rtment of Health and Human Services 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health 
Report of Investigations 9659 

Evaluation of Explosion-Resistant Seals, 

Stoppings, and Overcast for Ventilation 

Control in Underground Coal Mining 

By Eric S. Weiss, Kenneth L. Cashdollar, 

and Michael J. Sapko 
Report of Investigations 9659 

Evaluation of Explosion-Resistant Seals, 

Stoppings, and Overcast for Ventilation 

Control in Underground Coal Mining 

By Eric S. Weiss, Kenneth L. Cashdollar, 

and Michael J. Sapko 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Public Health Service 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health 

Pittsburgh Research Laboratory 

Pittsburgh, PA 

December 2002 
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DHHS (NIOSH) Publication No. 2003-104 
Page 

Abstract ...................................................................................... 1 

Introduction ................................................................................... 2 

Experimental mine and test procedures .............................................................. 2 

Mineexplosiontests .......................................................................... 2 

Instrumentation .............................................................................. 5 

Airleakagedetenninations ..................................................................... 6 

Cementitious pumpable plug seals .................................................................. 7 

Construction ................................................................................ 7 

Explosion and air leakage test results ............................................................. 10 

Australian design seals. stoppings. and overcast ....................................................... 12 

Construction of seals. stoppings. and overcast ...................................................... 12 

Seals ................................................................................... 13 

Stoppings ................................................................................ 17 

Overcast ................................................................................. 18 

Explosion and air leakage test results ............................................................. 22 

First explosion test (LLEM test 358) ........................................................... 22 

Second explosion test (LLEM test 359) ......................................................... 24 

Third explosion test (LLEM test 360) .......................................................... 24 

Fourth. fifth. and sixth explosion tests (LLEM tests 361.362. and 363) ................................ 26 

Seventh explosion test (LLEM test 364) ......................................................... 27 

Preloaded solid-concrete-block seal designs for friable rib conditions ...................................... 29 

Construction ................................................................................ 29 

Explosion and air leakage test results ............................................................. 31 

Conclusions ................................................................................... 32 

Acknowledgments ........................................................................... 33 

References .................................................................................. 34 

Appendix A.-Summary tables of air leakage measurements ............................................. 35 

Appendix B.-Summary tables of static pressure data for LLEM explosion tests .............................. 39 

Appendix C.-Summary table of flame arrival data for LLEM explosio~n tests ................................ 45 

Appendix D.-Summary tables of LVDT displacement data for LLEM explosion tests ......................... 46 

1 . Plan view of the Lake Lynn Experimental Mine ................................................. 3 

2 . SealtestareaintheLLEM .................................................................. 3 

3 . LVDTattachedtoaseal ................................................................... 5 

4 . Support posts and instrumentation on the back side of a seal ....................................... 5 

5 . Pressurized entry for leakage determination rates across the seals ................................... 6 

6 . Brattice in place for seal leakage test .......................................................... 7 

7 . Construction of the wood and brattice cloth form walls used to contain the pumpable cementitious grout slurry 8 

8 . Slurry injection using the three injection ports located near the mine roof ............................. 8 

9 . Completed ribfill seal in crosscut 3 ........................................................... 10 

10 . Horizontal cracks evident near the mine roof on the ribfill seal iin crosscut 3 after test 354 ................ 11 

11 . Schematic of vinyl bladder with internal baffles used for constru~ction of the seal and overcast designs ...... 14 

12 . Spreader bar anchored to the mine roof used to support the seal bladder system ........................ 14 

13 . Shotcreting of the spreader bar and hook assembly ............................................... 14 

14 . Inflated vinyl bladder assembly showing the injection port for the piers ............................... 14 

15 . Framework for construction of seal in crosscut 2 ............................................... 15 

16 . Construction of seal in crosscut 2 showing vinyl bladder in place, but not yet filled ..................... 15 

17 . Completed seal in crosscut 2 ................................................................ 15 

18 . Construction of seal in high roof section of crosscut 3, showing the vinyl bladder being installed ........... 16 

19 . Construction of seal in hgh roof section of crosscut 3, showing the grout injection hose attached to the bladder .... 16 
CONTENTS-continued 

Page 

20 . Construction of seal in crosscut 4 showing the vinyl tubes before filling .............................. 16 

2 1 Construction . of second seal in high roof section of crosscut 3 ...................................... 16 

22 . Construction of seal in crosscut 4 showing details of the tops of the vinyl tubes and light meshing overlay .... 17 

23 . Construction of water stopping in crosscut 3, with the individual tubes suspended from the roof-mounted 

spreaderbar ........................................................................... 17 

24 . Details of the Velcro and plastic clip fastening system for the water stopping in crosscut 3 ................ 18 

25 . Schematic drawing of overcast at the intersection of B-drift and crosscut 3 ............................ 18 

26 . Construction of side wall of overcast at the intersection of B-drift and crosscut 3 ....................... 19 

27 . Construction of overcast at the intersection of B-drift and crosscut 3: installation of deck on top of side wall . . 19 

28 . Construction of overcast at the intersection of B-drift and crosscut 3: installation of skirt around edge of deck 20 

29 . Top view of overcast deck showing reinforcing bars .............................................. 20 

30 . View underneath the overcast deck showing temporary supports while the deck cement cured ............. 20 

3 1 . Construction of wing wall along edge of overcast deck: side view of vinyl bladder for wing wall being installed ... 2 1 

32 . Construction of wing wall along edge of overcast deck: end view of wing wall above deck ............... 21 

33 . Completed overcast viewed from under the deck ................................................ 21 

34 . Side wall of overcast, as viewed from B-drift outby, showing instrumentation boxes and support frames ..... 21 

35 . Instrumentation on top of overcast deck: three LVDTs suspended above deck ......................... 21 

36 . Closeup of LVDT suspended from roof and attached to deck ....................................... 21 

37 . Completed water stopping in crosscut 3 ....................................................... 22 

38 . Release of individual water tubes of stopping during air leakage test ................................. 22 

39 . Air-inflated vinyl bladder of quickseal in crosscut 4 .............................................. 22 

40 . Condition of water stopping in crosscut 3 after test 358 ........................................... 23 

41 . Completed seal in the high roof section of crosscut 3 ............................................. 23 

42 . Pressure traces as a function of distance from the closed end (face) in C-drift for test 359 ................. 24 

43 . Seal in crosscut 2 after test 359 .............................................................. 24 

44 . Seal in crosscut 3 after test 359 .............................................................. 25 

45 . Seal in crosscut 2 after test 360 .............................................................. 25 

46 . Pressure and LVDT traces for seal 2 during test 360 .............................................. 26 

47 . Remains of crosscut 3 seal after test 360 ....................................................... 26 

48 . Pressure and LVDT traces for seal 3 during LLEM test 360 ........................................ 26 

49 . Pressure and LVDT traces for overcast during LLEM test 363 ...................................... 27 

50 . Completed new (second) seal in high roof section of crosscut 3 ..................................... 28 

5 1 . Completed new seal in crosscut 4 ............................................................ 28 

52 . Remains of crosscut 4 seal after test 364 ....................................................... 28 

53 . Unfilled Packsetter bags at the seal interface with the mine roof and ribs .............................. 30 

54 . Filled and pressurized Packsetter bags at the outby roof and rib seal interface showing full-size bags and one 

half-sizebagontheleft .................................................................. 30 

55 . Placement of the Packsetter bag at the mine rib and floor interface with the bottom course of the tongueand-groove solid-concrete-block seal ........................................................ 30 

56 . Hand-powered pump for filling the Packsetter bags .............................................. 30 

57 . Completed mortared seal with the Packsetter bags and floor hitching in crosscut 2 ...................... 31 

58 . Completed mortared seal with the Packsetter bags in crosscut 3 ..................................... 31 

59 . Mortared seal with floor hitching and Packsetter bags in crosscut 2 after test 366 ....................... 32 

60 . Mortared seal with Packsetter bags in crosscut 3 after test 366 ...................................... 32 

61 . Remains of the dry-stacked seal with the Packsetter bags in crosscut 4 after test 366 ..................... 32 

TABLES 

1 . Lake Lynn Experimental Mine explosion tests .................................................. 4 

2 . Guidelines for air leakage through a seal ....................................................... 7 

3 . Constmction schedule at the Lake Lynn Experimental Mine ........................................ 9 

4 . Sealsandstoppingssizedata ................................................................ 9 

5 . Evaluations of the seal, stopping. and overcast designs ............................................ 11 
Page 

A.1 . Air leakage measurements before the first explosion test (No . 35#4) of the HeiTech program ............... 

A.2 . Air leakage measurements after the first explosion test (No . 354) of the HeiTech program ................ 

A.3 . Air leakage measurements after sealant was reapplied and before: the second explosion test (No . 355) 

oftheHeiTechprogram .................................................................. 

A.4 . Air leakage measurements after the second explosion test (No . 3.55) of the HeiTech program .............. 

A.5 . Air leakage measurements before the first explosion test (No . 358) of the Barclay Mowlem program ........ 

A.6 . Air leakage measurements between the first (No . 358) and second (No . 359) explosion tests of the Barclay 

Mowlemprogram ....................................................................... 

A.7 . Air leakage measurements between the second (No . 359) and third (No . 360) explosion tests of the Barclay 

Mowlemprogram ....................................................................... 

A.8 . Air leakage measurements between the third (No . 360) and fourth (No . 361) explosion tests of the Barclay 

Mowlemprogram ........................................................................ 

A.9 . Air leakage measurements between the fourth (No . 361) and fifth (No . 362) explosion tests of the Barclay 

Mowlemprogram ........................................................................ 

A- 10 . Air leakage measurements before the seventh explosion test (No . 364) of the Barclay Mowlem program ..... 

A-1 1 . Air leakage measurements after the seventh explosion test (No . 364) of the Barclay Mowlem program ...... 

A-12 . Air leakage measurements before the first explosion test (No . 365) of the Packsetter seal program with the 

solidconcreteblock ...................................................................... 

A-13 . Second air leakage measurements before the first explosion test (No . 365) of the Packsetter seal program with 

thesolidconcreteblock .................................................................. 

A.14 . Air leakage measurements between the first (No . 365) and sec0n.d (No . 366) explosion tests of the Packsetter 

seal program with the solid concrete block ................................................... 

A- 15 . Air leakage measurements after the second explosion test (No . 366) of the Packsetter seal program with the 

solidconcreteblock ..................................................................... 

B-1 . HeiTech pumpable cementitious seals evaluation in the Lake Lynn Experimental Mine: pressure data. test 354 

B.2 . HeiTech pumpable cementitious seals evaluation in the Lake Lynn Experimental Mine: pressure data. test 355 

B.3 . Barclay Mowlem seal and stoppings evaluation in the Lake Lymi Experimental Mine: pressure data. 

test358 ............................................................................... 

B.4 . Barclay Mowlem seals evaluation in the Lake Lynn Experimental Mine: pressure data. test 359 ........... 

B.5 . Barclay Mowlem seals evaluation in the Lake Lynn Experimental Mine: pressure data. test 360 ........... 

B.6 . Barclay Mowlem seals and overcast evaluation in the Lake Lynr~ Experimental Mine: pressure data. 

test361 ............................................................................... 

B.7 . Barclay Mowlem seals and overcast evaluation in the Lake Lynr~ Experimental Mine: pressure data. 

test362 ............................................................................... 

B.8 . Barclay Mowlem seals and overcast evaluation in the Lake Lynr~ Experimental Mine: pressure data. 

test363 ............................................................................... 

B.9 . Barclay Mowlem seals and overcast evaluation in the Lake Lynn Experimental Mine: pressure data. 

test364 ............................................................................... 

B.10 . Packsetter solid-concrete-block seals evaluation in the Lake Lynn Experimental Mine: pressure data. test 365 

B-1 1 . Packsetter solid-concrete-block seals evaluation in the Lake Lynn Experimental Mine: pressure data. test 366 

C- 1 . HeiTech and Packsetter seals evaluation in the Lake Lynn Experimental Mine: flame arrival time data ...... 

C.2 . Barclay Mowlem seals. stoppings, and overcast evaluation in the Lake Lynn Experimental Mine: flame arrival 

timedata .............................................................................. 

D.1 . Barclay Mowlem seals evaluation in the Lake Lynn Experimental Mine: LVDT data. test 358 ............ 

D.2 . Barclay Mowlem seals evaluation in the Lake Lynn Experimental Mine: LVDT data. test 359 ............ 

D.3 . Barclay Mowlem seals evaluation in the Lake Lynn Experimental Mine: LVDT data. test 360 ............ 

D.4 . Overcast LVDT data. test 361 ............................................................... 

D.5 . Overcast LVDT data. test 362 ............................................................... 

D.6 . Overcast LVDT data. test 363 ............................................................... 

D.7 . Seal LVDT data. test 363 ................................................................... 

D.8 . Overcast LVDT data. test 364 ............................................................... 

D.9 . Seal LVDT data. test 364 ................................................................... 
L liter OC degree Celsius 

lb pound OF degree Fahrenheit 
EVALUATION OF EXPLOSION-RESISTANT SEALS, STOPPINGS, 

AND OVERCAST FOR VENTll-ATlON CONTROL 

IN UNDERGROUND COAL MINING 

By Eric S. Weiss,' Kenneth L. Ca~hdollar,~ and Michael J. Sapko3 

ABSTRACT 

A fundamental safety research area for the National Institute for Occupational Safety and Health (NIOSH) 

is to eliminate the occurrence of coal mine explosions or to mitigate their effects. One approach is to develop 

and evaluate new and innovative seal designs that provide increased explosion protection for mining personnel. 

The NIOSH Pittsburgh Research Laboratory (PRL) cooperated with HeiTech Corp. of Virginia, Barclay 

Mowlem Construction Ltd. of Queensland, Australia, and the Mine Safety and Health Administration (MSHA) 

in three separate research programs to evaluate the strength characteristics and air leakage resistance of 

numerous innovative seal designs and ventilation control structuires for use in underground coal mines. For each 

phase of the program, various full-scale seals, stoppings, and an overcast design were constructed in PRL's Lake 

Lynn Experimental Mine near Fairchance, Fayette County, PA. The seals and stoppings were built in crosscuts 

and were subjected to explosions to evaluate their strengths. 

Four pumpable cementitious seal designs ranging in thickness from 610 to 915 mm (24 to 36 in) were 

evaluated in the first cost-reimbursable research program with HeiTech Corp. A simple wooden framework 

with brattice liner was used as a form to contain the cementitious slurry during the curing period. As the seal 

designs decreased in thickness, higher compressive strength cementitious grout was used. All four seals 

withstood an explosion pressure pulse of at least 138 kPa (20 psi) while maintaining acceptable air leakage 

resistance. 

In the second cost-reimbursable research program with Bai:clay Mowlem Construction Ltd. of Australia, 

several innovative seal and stopping designs and an overcast design were evaluated. Each of the seal designs 

and the overcast side and wing walls used one or more air-inflated vinyl bladder assemblies anchored to the 

mine roof and hitched into the ribs and floor. The air within these bladders was displaced with a high-strength 

cementitious grout. The overcast deck consisted of a 200-mm ('7.8-in) thick reinforced cementitious slab. This 

was the first time that an overcast structure had been explosion tested under full-scale conditions. All of the 

seals, stoppings, and overcast design passed the air leakage tests before being subjected to a series of explosions 

with static pressure pulses ranging from 14 to 475 kPa (2 tab 69 psi). Instrumentation measured seal and 

overcast wall displacement as a function of time. The 450-mm (1 7.7-in) thick seal in the 2.8-m(9-ft) high third 

crosscut withstood an explosion pressure of 170 kPa (25 psi), but failed during a later test, which generated a 

peak static pressure of 475 kPa (69 psi) at the seal location. A similar 450-mm-thick seal in the 2.1-m (7-ft) 

high second crosscut withstood three explosion tests, which generated peak static pressures of 195, 205, and 

370 kPa (28, 30, and 54 psi) at the seal location. Next, the overcast design withstood four explosions, which 

generated static overpressures ranging from 16 to 47 kPa (2.3 to 6.8 psi). 

A third program at the request of MSHA evaluated the effectiveness of using pressurized grout bags 

(Packsetter bags) along the mine roof and ribs in lieu of floor and rib hitching for a standard-type solidconcrete-block seal. This program was initiated to address an urlusual geological mining condition encountered 

when building seals in entries where required rib hitching is not a viable option due to soft friable coal. Results 

showed that the use of these quick-setting grout-filled Packsetter bags pressurized internally to 300 kPa (44 psi) 

not only provides a seal that can withstand a 138-kPa static pressure explosion, but also provides a sealing 

option where rib hitching is not possible. 

'Supervisory mining engineer. 

'Research physicist. 

'Senior research physical scientist. 

Pittsburgh Research Laboratory, National Institute for Occupational Safety and Health, Pittsburgh, PA. 
INTRODUCTION 

During the course of underground coal mining it is 

sometimes necessary to install seals to isolate abandoned or 

worked-out areas of a mine. This eliminates the need to 

ventilate those areas. Seals are also used to isolate fire zones or 

areas susceptible to spontaneous combustion. To effectively 

isolate areas within a mine, a seal mustMinimize leakage between the sealed area and the active 

mine workings so as to prevent toxic andlor flammable gases 

from entering the active workings; 

Be capable of preventing an explosion initiated on one side 

from propagating to the other side; and 

Continue its intended function for 1 hr when subjected to 

fire conditions. 

30 CFR' 75.335 [I9971 requires a seal to "withstand a static 

horizontal pressure of 20 pounds per square inch (1 38 kPa)." 

Previous research by the U.S. Bureau of Mines (USBM) 

[Mitchell 19711 indicated that it would be unllkely for 

overpressures >I38 kPa to occur very far from the explosion 

origin provided that the area on either side of the seal contained 

sufficient incombustible and minimal coal dust accumulations. 

This regulation formed the basis for previous evaluations of 

explosion-resistant seals at the Lake Lynn Experimental Mine 

(LLEM) [Stephan 1990a,b; Greninger et al. 1991; Weiss et al. 

1993a,b,c; 1996; 1997; 19991. 

The Pittsburgh Research Laboratory (PRL) and the Mine 

Safety and Health Administration (MSHA) have been jointly 

evaluating the capability of various seal construction materials 

and designs to meet or exceed the requirements of the CFR. 

This work is in support of PRL's Disaster Prevention and 

Response Research Program to improve safety for underground 

mine workers. These have been the first full-scale research 

programs to evaluate seal designs in entry geometries similar to 

those of current U.S. underground coal mines. Past seal 

research program had addressed, through explosion testing at 

the LLEM, the integrity of solid-concrete-block seals [Stephan 

1990a; Greninger et al. 199 11, low-density cementitious block 

seals [Stephan 1990b; Weiss et al. 1993~1, cementitious foam 

seals [Stephan 1990a; Greninger et al. 1991; Weiss et al. 

1993~1, wood-block seals [Weiss et al. 1993~1, cellular concrete 

seals [Weiss et al. 19961, and polymer seals [Weiss et al. 19961. 

The overall objective of this research is to determine whether 

seals built from various materials and designs can withstand a 

13 8-kPa explosion pressure pulse without losing their structural 

integrity. The seal must not only be physically strong, but also 

minimize air leakage. A safety benefit will also result from 

these evaluations in that many of these new seal designs require 

less materials handling and fewer worker-hours to install than 

the standard-type solid-concrete-block seal. 

This report discusses the construction techniques, testing 

methods, and explosion test data collected for the pumpable 

cementitious seals; the seal, stopping, and overcast designs for 

the Australian program; and the Packsetter preloaded solidconcrete-block seal. 

EXPERIMENTAL MlNE AND TEST PROCEDURES 

MINE EXPLOSION TESTS 152 m long and connects drifts C and D. The drifts and 

All of the explosion and air leakage determination tests were 

done at the LLEM [Mattes et al. 1983; Triebsch and Sapko 

19901. Lake Lynn Laboratory is located about 80 km southeast 

of Pittsburgh, near Fairchance, Fayette County, PA. It is one of 

the world's foremost mining laboratories for conducting largescale health and safety research. The LLEM is unique in that it 

can simulate current U.S. coal mine geometries for a variety of 

mining scenarios, including multiple-entry room-and-pillar 

mining and longwall mining. 

Figure 1 shows a plan view of the LLEM. The underground 

entries consist of about 7,620 m of old workings developed in 

the mid-1960s for the commercial extraction of limestone and 

2,370 m of new entries developed by the USBM in 1980-8 1 for 

research [Mattes et al. 19831. These more recent entries are 

depicted in figure 1 as drifts A through D, each of which is 

-520 m long and closed at the inby end, and drift E, which is 

4Code of Federal Regulalions. See CFR in references. 

crosscuts range from 5.5 to 6.0 m wide and are about 2 m high. 

The LLEM was designed to withstand explosion overpressures 

up to -700 kPa (100 psi). During 1982-2001, a total of 406 

consecutively numbered explosion tests were conducted at the 

LLEM. 

Figure 2 shows a closeup view of the seal test area in the 

multiple-entry section of the LLEM. All of the seals and 

stoppings were built in the crosscuts between B- and C-drifts. 

The roof in one section of crosscut 3 had been enlarged 

previously to -2.8 m high to more closely represent those of 

typical Australian and some U.S. underground coal mines 

[Weiss et al. 19991. The roof in the intersection of B-drift and 

crosscut 3 was enlarged during this series of tests to 

accommodate the overcast design. Details on the designs for the 

seals, stoppings, and overcast are found in the "Construction" 

section for each of the three programs found later in this report. 

Before each explosion test, a 60-t hydraulically operated, 

track-mounted, concrete and steel bulkhead was positioned 

across E-drift to contain the explosion pressures in C-drift 
Surface quarry 7 

Ventilation shaft 

0 - 50 100 

Scale, m 

Legend - Data-gathering station 

Figure 1.-Plan view of the Lake Lyn~n Experimental Mine. 

(figure 2). For a typical evaluation test on a seal design for use 

in a U.S. coal mine, 18.7 m3 (66 1 f?) of natural gas (-97% CH,) 

was injected into the closed end of C-drift. An electric fan with 

an explosion-proof motor housing was used to mix the natural 

gas with the air in the ignition zone. A plastic diaphragm was 

used to contain the natural gas and air mixture within the first 

14.3 m of the entry, resulting in a -2 10-m3 gas ignition zone. 

Sample lines within the ignition zone were used to continuously 

monitor the gas concentrations using an infrared analyzer. In 

addition, samples were collected in evacuated test tubes and sent 

to the PRL analytical laboratory for more accurate analyses 

using gas chromatography (GC). The GC analyses verified the 

infrared analyzer readings of -9% of methane in air. Three 

electrically activated matches, in a triple-point configuration 

equally spaced across the face (closed end) of the entry, were 

used to ignite the flammable natural gas and air mixture. Barrels 

0 

Ld 

30 

Scale, m 

legend 

Data-gathering station - 

- 1 Crosscut 

filled with water were located in the gas ignition zone to act as Figure 2.-Seal test area in the LLEM. 

turbulence generators to achieve the projected -140-kPa 

(20-psi) pressure pulse. The pressure pulse generated by the section) than in smaller entries such as in PRL's Bruceton 

ignition of this methane-air zone generally resulted in static Experimental Mine (-5-m2 cross section), presumably because 

pressures ranging from -1 50 kPa at crosscut 1 to -1 15 kPa at of the smaller surface-to-volume ratio at the LLEM [Sapko et al. 

the most outby location (in some instances as far outby as 19871. 

crosscut 5, or 150 m from the ignition source). Explosion S~unmary data for the 1 1 explosion tests from the programs 

studies have shown that the explosion pressure pulse decays less discussed in this report are found in table 1. In the table, the 

rapidly with distance in the larger LLEM entries (-1 3-m2 cross tests are identified chronologically within each of the three 
Table 1.-Lake Lynn Experimental Mine explosion tests 

Average maximum Average flame 

Test No. Date pressure' speed2 Fuel type 

psi kPa m/s 

HEITECH PROGRAM 

354 . . . . . Nov. 6,1997 . . . . . . 24 165 NA 18.7-m3 CH, + 14.5kg coal. 

355 . . . . . Nov. 20,1997 . . . . . 23 160 -190 (26-71 m) 18.7-m3 CH, + 14.5kg coal. 

BARCLAY MOWLEM PROGRAM 

358 . . . . . Feb. 11,1998 . . . . . 3.2 22 - 8.2-m3 CH,. 

359 . . . . . Feb. 27,1998 . . . . . 27 185 -225 (26-93 m) 18.7-m3 CH, + 14.5kg coal. 

360 . . . . . Mar. 3,1998 . . . . . . 63 435 -385 (26-93 m) 18.7-m3 CH, + 120-kg coal. 

361 . . . . . Mar. 26,1998 . . . . . 2.7 19 - 8.2-m3 CH,. 

32.3 6 

362 . . . . . Mar. 31, 1998 . . . . . 5.1 35 - 9.0-m3 CH,. 

34.3 330 

363 . . . . . Apr. 1,1998 . . . . . . 7.7 53 -1 60 (26-41 m) 9.6-m3 CH,. 

36.8 347 

364 . . . . . Apr. 3,1998 . . . . . . 23 160 -340 (26-56 m) 18.7-m3 CH, + 7.3-kg coal. 

93.0 341 

PACKSETTER SEALS WITH SOLID-CONCRETE-BLOCK 

365 . . . . . June 22, 1998 . . . . . 20 140 -380 (26-41 m) 18.7-m3 CH,. 

366 . . . . . June 25,1998 . . . . . 23 160 -1 90 (26-71 m) 18.7-m3 CH, + 14.5-kg coal. 

'Average static pressures calculated in C-drift from 26 m to transducer just beyond last seal. 

'Average flame speed calculated over distances (m) in C-drift, as noted in parentheses. 

%tatic pressure in crosscut 3, leading to overcast. 

programs and also by the LLEM test number. Most of the tests 

(354, 355, 359, 364, 365, and 366) were set up in a similar 

manner to that described in the above paragraph, with a -2 1 0-m3 

gas ignition zone. To ensure that all of the seal designs would 

see at least a 140-kPa explosion pressure pulse, a small amount 

of coal dust was used for several of these tests in addition to the 

gas ignition zone (see last column of table 1). The coal dust was 

loaded onto shelves suspended from the mine roof on 3-m 

increments starting 13 m from the closed end (near the end of 

the gas ignition zone). For tests 354 and 355 of the HeiTech 

program, test 359 of the Barclay Mowlem program, and test 366 

of the Packsetter program, 14.5 kg of coal dust was loaded 

equally onto four shelves from 13 to 23 m from the closed end. 

The nominal coal dust concentration of this -1 2-m-long dusted 

zone was -100 g/m3. When ignited, this coal dust increased the 

average explosion overpressure from -140 kPa for the pure gas 

zone (test 365 plus some earlier tests) to -166 kPa (24 psi) for 

tests with the hybrid gas-dust ignition zone. During the seventh 

Barclay test (LLEM test 364), only 7.3 kg of coal dust was 

loaded onto two shelves at 13 and 17 m from the closed end. 

When ignited, this ignition zone resulted in a slightly lower 

explosion overpressure. The average explosion pressures in 

table 1 were calculated from the pressure transducers in C-drift 

from 26 m to just beyond the last seal tested. For explosions 

with pressures >I40 kPa (20 psi), the pressures in table 1 were 

rounded to the nearest 5 kPa (1 psi). The average flame speeds 

listed in table 1 were calculated from the flame arrival times 

listed in appendix C. 

To acheve an explosion pressure pulse significantly in 

excess of 140- 166 kPa, a larger quantity of coal dust was placed 

on shelves for a longer distance outby the gas ignition zone in 

C-drift. During the third explosion test (LLEM test 360) of the 

Barclay Mowlemprogram, a 64-m-long zone of coal dust (13 to 

78 m from the closed end) was used in addition to the gas 

ignition zone. The pulverized coal dust (Pittsburgh Seam 

bituminous) was loaded onto the shelves to provide a nominal 

coal dust concentration of 150 g/m3; this assumed a uniform 

dispersion of the coal dust over the entire cross section of the 

mine entry. A total of 120 kg of coal dust was used during ths 

third seal evaluation test. This gas and coal dust mixture 

produced an explosion with an average overpressure of 435 kPa 

(63 psi). 

To achieve the low explosion pressures (<70 kPa) necessary 

to evaluate the stopping and overcast designs during the first, 

fourth, fifth, and sixth tests (LLEM tests 35 8, 36 1-363) of the 

Barclay Mowlem program, the length of the gas ignition zone 

was reduced from 14.3 m to only 8.2 m from the closed end of 

C-drift, giving an ignition volume of-1 15 m3. During tests 358 

and 361, 8.2 m3 (290 ff) of natural gas was injected within the 

gas zone, giving a methane concentration of -7%. When 

ignited, the resulting gas explosions produced average overpressures in C-drift of -20 kPa (3 psi). The small decrease in 

the average overpressure from test 358 to test 361 was mainly 

due to the number and types of ventilation structures being 

evaluated at the time. During test 362, 9.0 m3 (319 ff) of 

natural gas was used and resulted in an average explosion 

overpressure in C-drift of about 35 kPa (5.1 psi). During 

test 363,9.6 m3 (340 ft?) of natural gas was used and resulted in 

an average explosion overpressure in C-drift of about 53 kPa 

(7.7 psi). The pressures in the overcast area were somewhat 

lower, as noted in table 1. 
approximately the total pressure (combination of static and 

dynamic pressures) generated on the stoppings/seals during each 

of the explosion tests. The reason that the pressures may not 

have been quite equal to the true total pressures was that the 

housings were not designed in an ideal manner to measure the 

dynamic part of the total pressure. The "total" pressure data 

from these transducers located in front of the stoppings/seals 

were higher than the interpolated static pressure data. 

An additional type of sensor was used during the Barclay 

Mowlem and Packsetter seal evaluation programs: linear 

variable differential transducers (LVDTs) to measure movement 

of the seals. The LVDT is shown attached to the back (B-drift 

side) of a seal in figure 3.5 The Schlumberger Industries LVDTs 

provide a reliable method for precision measurement of linear 

displacement in the direction of the wall movement, perpendicular to the plane of the seal or overcast wall or deck. The 

LVDT is calibrated by varying the position of the core (the thin 

rod extending out from the cylindrical housing in figure 3) by 

known distances and then measuring the corresponding output 

voltages. Each LVDT was attached to an aluminum housing 

that was clamped to a steel post behind the seal, as shown in 

5~11 photographs in this report were taken by Eric S. Weiss, Kenneth L. 

Cashdollar, or William A. Slivensky of the NIOSH Pittsburgh Research 

Lsboratory. 

Figure 4.--Support posts and instrumentation on the back side 

of a seal. 

figure 4. The square cross-section posts were bolted to the roof 

and floor. The main cylindrical body of each LVDT was held 

by the aluminum block, as shown held by the engineer in 

figure 3. The movable thin rod extending from the LVDT was 

attached to a small plate that was epoxied to the back face of the 

seal. These sensors were then interfaced to the.nearest datagathering station. 

During the first test ofthe Barclay Mowlemprogram, the seal 

in crosscut 2 was instrumented with four LVDTs on the B-drift 

side (side of the seal opposite to the explosion). One LVDT was 

installed at the exact center (midheight and midwidth) of the 

seal (referred to as "middle" in the tables in appendix D). This 

is the sensor that is slightly below and to the right of the 

instrumentation box on the left post in figure 4. A second 

LVDT was installed at a three-quarter height and rnidwidth 

point (above and to the right of the left instrumentation box in 
figure 4). (This is referred to as "upper" in the tables in 

appendix D.) A third LVDT was installed at a one-quarter 

height and midwidth point on the left post (referred to as 

"bottom" in the tables in appendix D). The fourth LVDT was 

installed at midheight and quarter-width (halfway between the 

seal center and the outby rib, just below the instrumentation box 

on the right post in figure 4). No sensors were installed on any 

of the stoppings since they were designed to release and vent the 

explosion overpressures. The overcast was instrumented with 

LVDTs (in a pattern similar to that used for the seals) on the 

outby B-drift side wall. Three LVDTs were also used on the 

overcast deck to measure the displacement of the deck. One 

LVDT was used for one of the overcast wing walls. Details of 

the instrumentation for the overcast are in the "Overcast" section 

for the Australian program found later in this report. For 

stronger explosion tests in which the seals and overcast had the 

potential to fail, some or all of the expensive LVDT sensors 

were removed so that they would not be destroyed. 

The data gathered during the explosion tests were relayed 

from each of the data-gathering stations to an underground 

instrument room off of C-drift and then to an outside control 

building. A high-speed, 64-channel, PC-based computer data 

acquisition system was used to collect and analyze the data. 

This system collected the sensor data at a rate of 1,500 samples 

per channel over a 5-s period. The data were then processed 

using LabView, Excel, and PSI-Plot software and outputted in 

graphic and tabular fonn, as will be shown and discussed in the 

"Explosion and Air Leakage Test Results" sections for each of 

the three programs found later in this report. The reported data 

were averaged over 10 ms (1 5-point smoothing). This PC data 

analysis system allowed the data traces to be expanded in time 

and pressure (or other sensor value) so that the peak values 

could be read and recorded precisely. 

AIR LEAKAGE DETERMINATIONS 

An important factor to be considered for any seal design is its 

ability to minimize air leakage through the seal. Measurements 

of air leakages across the seals, stoppings, and overcast were 

taken before and after each of the explosion tests. For these air 

leakage tests, the D-drift bulkhead door (see figure 1) was 

closed. This directed all of the ventilation flow (from a vertical 

air-shaft in E-dnft) toward C-dnft. A wooden framework with 

brattice cloth or curtain was erected across C-drift outby the last 

seal or stopping position (figure 5). This curtain effectively 

blocked the ventilation flow, which resulted in a pressurized 

area on the C-drift side of the seals, stoppings, and overcast. By 

increasing the speed of the four-level LLEM main ventilation 

fan while in the blowing mode, the resultant pressure exerted on 

the structures increased from about 0.25 Wa (1-in H20) for the 

lowest fan speed setting to nearly 1.0 Ha (3.7-in H20) for the 

highest fan speed setting. 

On the B-drift side of each seal and stopping design, 

a diaphragm of brattice cloth was installed across each crosscut 

(figure 5). A typical brattice with a 465-cm2 opening near the 

Figure 5.-Pressurized entry for leakage determination rates 

across the seals. 

center is shown in figure 6. For the Barclay Mowlem overcast 

air leakage tests, three diaphragms were constructed: one inby 

the overcast in B-drift, one outby the overcast in B-drift, and 

one in the crosscut between A- and B-drifts. The 465-cm2 

center opening was only on pne of these brattices. A vane 

anemometer was used to monitor the airflow through these 

openings on the brattices to determine the leakage rates through 

each design (figure 6). During construction of the seals, 

stoppings, and overcast, a copper tube was positioned through 

each of these structures with one end of the tube extending out 

on either side. This tube served as a way of measuring the air 

pressure exerted by the fan on each structure. During these air 

leakage tests, a pressure gauge was attached to the copper tube 

on the B-drift side to monitor the differential pressure across the 

structure. 

As the ventilation fan speed was increased, the pressures on 

and the airflows through each structure were recorded. Based 

on data previously collected during the testing program with 

solid-concrete-block and cementitious foam seals [Stephan 

1990a; Greninger et al. 199 11, U.S. guidelines for acceptable air 

leakage rates through seals were developed for the LLEM seal 

evaluation programs. The air leakage rates through the seals 

during both pre- and postexplosion leakage tests were evaluated 

against these established guidelines. Table 2 lists these 

maximum acceptable air leakage rates as a function of pressure 

differential. For pressure differentials up to 0.25 kPa (1-in 

H20), air leakage through the seal must not exceed 2.8 m3/min 

(100 ch). For pressure differentials over 0.75 Wa (3-in H20), 

air leakage must not exceed 7.1 m3/min (250 ch). The flow 

rate was calculated from the linear air speed measured by the 

vane anemometer and the area of the opening through the 

brattice cloth behnd each seal. 

When a postexplosion visual inspection of any seal revealed 

substantial structural damage, that seal was considered not 

to meet the minimum standards as specified in the CFR for 

an underground coal mine seal and therefore "failed." 
were designed to partially vent the explosion pressure. >0.75 . . . . . . . . >3.0 ~7.1 <250 

CEMENTITIOUS PUMPABLE PLUG SEALS 

Since 1990, several research programs have been conducted 

at the LLEM to evaluate the strength characteristics and air 

leakage resistance ofpumpable cementitious plug seals [Stephan 

1990a; Greninger et al. 1991; Weiss et al. 1993c; 1996; 19991. 

These types of plug seal designs are not required to be hitched 

or keyed into the mine ribs and floor. Test results from those 

programs have shown that for a pumpable cementitious seal 

design to be deemed suitable by MSHA for use in an underground coal mine, that seal must be at least 1.2-m (4-ft) thick 

with a minimum grout compressive strength of 1.4 MPa 

(200 psi). Several seals using either cement foams [Stephan 

1990a; Greninger et al. 199 11 or cellular concretes [Weiss et al. 

19961 are currently in use today in coal mines as a direct result 

of these LLEM seal evaluation programs. 

In 1997, HeiTech Corp. entered into an agreement with PRL 

to evaluate four new cementitious pumpable seal designs. 

Under the agreement, HeiTech reimbursed NIOSH for all 

expenses incurred by NIOSH during this program. The seals 

were installed by HeiTech personnel. The following two 

sections discuss the construction process and the performance of 

these seals when subjected to a 138-kPa explosion pressure 

pulse. 

CONSTRUCTION 

As ~lth te previously evaluated pumpable cementitious seal 

designs, these new HeiTech designs used a similar wooden 

framework and brattice liner to contain the cementitious slurry. 

Before installing these form walls, the concrete mine floor of the 

LLEM was roughened. (In a coal mine installation, the mine 

floor must be cleaned to the solid.) All loose material was 

removed from the LLEM roof, ribs, and floor. No hitching or 

keying of the seal is required with pumpable cementitious seal 

designs. The upright posts of the walls consisted of 15- by 

15-cm (6- by 6-in) rough-cut posts wedged at the floor and roof 

(figure 7). The post pattern required a 76-cm spacing, with a 

maximum spacing not to exceed 9 1 cm. The end posts of each 

form wall are set as close to the rib as possible. The front form 
a 15-cm overlap to the inside mine surfaces. 

The cementitious slurry is mixed and pumped into each seal 

using a mixer-type placer pump. For each seal design, a threeport injection process was used during the pumping of the final 

slurry. These injectionports, with equal horizontal spacings, are 

Figure 7.--Construction of the wood and brattice cloth form 

walls used to contain the pumpable cementitious grout slurry. 

bolt extended into the seal. The floor bolts were embedded and 

grouted into the floor to a depth of about 0.8 m; the rest of the 

bolt extended into the seal. Next, the front and back form walls 

were installed. An aggregate was stowed between the two walls 

Figure 8.--Slurry injection using the three injection ports 

located near the mine roof. 
Table 3.--Construction schedule at the Lake Lynn Experimental Mine 

Shotcrete and Designltype Position Grout injection final installation Removal 

HEITECH PROGRAIbl 

Seal, hvdrocrete ...... Crosscut 2 .... Oct. 17, 1997 ............ - - . - Seal, ribfill ........... Crosscut 3 .... Oct. 15, 1997 ............ Seal, hydroseal ...... Crosscut 4 .... Oct. 16,1997 ............ 

stopping, water-filled .. Crosscut 3 .... - Feb. 7,1998 ............. After No. 358. 

Stopping, air-filled .... Crosscut 4 .... - Feb. 1 1,1998 ............ After No. 358. 

Seal ............... Crosscut 3, Feb. 17-1 8,1998 ......... Feb. 20,23,1998 ......... After No. 360. 

high roof. 

Overcast ............ Intersection of Mar. 7.9-1 1, 14, 16, 18-1!9, Mar. 11, 13, 17-21,23-24, - 

crosscut 3 and 1998. 1998. 

B-drift. 

New seal ........... Crosscut 4 .... Mar. 24,1998 ............ Mar. 24-25,1998 ......... - 

New seal ........... Crosscut 3, Apr. 1,1998 ............. Apr. 2,1998 ............. 7 

high roof. 

PACKSETTER SEALS WlTH SOLID-CONCRETE-BLOCK 

Seal, mortared ....... Crosscut 2 .... May 21,1998' ........... - - Seal, mortared ....... Crosscut 3 .... May 21,1998' ........... - - 

Seal, dry-stacked ..... Crosscut 4 .... May 19,1998' ........... May 20,1998' ........... - 

'Grout filling of Packsetter bags. 

'Sealant application to block wall. 

Table 4.--Seals and stoppinip size data 

Stoooinalseal size 

Designltype Position -- Thickness Width, Height, Area, 

mm in m m mz 

HEITECH PROGRAM 

Seal, hydrocrete ........ Crosscut 2 ........... 865, 34 5.9 2.1 12.4 

Seal, ribfill ............. Crosscut 3 ........... 91 51 36 5.9 2.1 12.4 

Seal. hydroseal ........ Crosscut 4 ........... 760 30 5.8 2.3 13.3 

Seal, hydroseal ........ Crosscut 5 ........... 61 0 24 6.0 2.2 13.2 

BARCLAY MOWLEM PROGRAM 

Stopping, water-filled .... Crosscut 3 ........... 170 7 5.9 2.1 12.4 

Stopping, air-filled ...... Crosscut 4 ........... 300 12 5.8 2.3 13.3 

Seal ................. Crosscut 2 ........... '4501 18 5.8 2.1 12.2 

Seal - ................. Crosscut 3, high roof ... '4501 18 5.9 2.8 16.5 

New seal ............. Crosscut 3, high roof ... '240 10 5.9 2.8 16.5 

New seal ............. Crosscut 4 ........... '165 7 5.8 2.3 13.3 

PACKSETTER SEALS WlTH SOLID-CONCRETE-BLOCK 

Seal, mortared ......... Crosscut 2 ........... '405 16 5.8 2.1 12.2 

Seal, mortared ......... Crosscut 3 ........... '405 16 5.9 2.1 12.4 

Seal, dry-stack ........ Crosscut 4 ........... '405 16 5.8 2.2 12.8 

'In addition, a 25-mm-thick coating of gunite was applied to C-drift side of each seal. ' -80-cm by -40-cm center pilaster. 

to a depth of -76 cm. The cementitious slurry was then pumped 

through a -1 5-m-long, 30-mm-diam hose to the seal location 

until the slurry filled the void spaces between the aggregate. 

Once the slurry level reached the top of the first aggregate lift, 

a 36-cm-high second lift of aggregate was stowed, followed by 

subsequent sluny injection. The third lift was similar to the 

second, and the fmal lift of 71 cm completed the seal. About 

12.5 t of aggregate and 157 bags, or 3,920 kg, of hydrocrete 

were used to build this seal. Compressive strength tests of the 

samples done by MSHA averaged -4.1*2.1 MPa (-600 psi); 

those by an independent lab, -5.W3.4 MPa (-840 psi). The 

differences in the compressive strength test results are, in 

part, due to the continuous injection process used during the 

construction of these seals. This means that the dry powder and 

water are continuously mixed as the seal is poured. This leads 

to more variability than a batch-mixing process where the exact 

amotu-its of dry powder and water can be blended together 

thorolughly before injection. Although there is considerable 

variation in the compressive strength data, the data fiom MSHA 

and the independent lab agreed to within the standard 

devia~tions. 
an independent lab, 2.7 1.2 MPa (390 psi). For the 610mm

thick crosscut 5 seal, the compressive strength tests of the 

sample cylinders tested by MSHA averaged -5.2*1.9 MPa 

(-750 psi); those by an independent lab, -4.12~1.9 MPa 

(-600 psi). 

also observed on the Cdrift (explosion) side of this seal where 

the explosion forces had pulled the brattice away from the 

seal (figure 10). Postexplosion air leakage rates for seal 3 

(table A-2) were well in excess of the established guidelines. 

After the postexplosion air leakage test, the front and back form 

Figure 9.--Completed ribfill seal in crosscut 3. the form walls were removed from each seal), the gaps between 
the ribfill grout and the mine roof were filled with ribfill grout 

for the seal in crosscut 3. The results of this second preexplosion air leakage test (table A-3 in appendix A) showed that 

all four seal designs were well within the established guidelines. 

The second explosion test subjected the seals to the following 

peak static pressures (details are in table B-2 and summarized in 

table 5): 190 kPa (27 psi) for the 860-mm-thick aggregate1 

hydrocrete design in crosscut 2, 165 kPa (24 psi) for the 

915-mm-thick ribfill design in crosscut 3, 150 kPa (22 psi) for 

the 760-mm-thick hydroseal design in crosscut 4, and 125 kPa 

(18 psi) for the 610-mm-thick hydroseal design in crosscut 5. 

The unsmoothed pressure data interpolated for seal 5 showed 

peaks >I38 kPa. Observations of the seals after the second 

explosion test (LLEM test 355) revealed no apparent damage to 

any of the four seals. Postexplosion air leakage measurements 

(table A-4) were within the established guidelines for all four 

seals. 

Figure 10.-Horizontal cracks evident near the mine roof on the Based on these results, MSHA has determined that these four 

ribfill seal in crosscut 3 after test 354, L~~~~ gaps between the HeiTech .seal designs are suitable for use in underground U.S. 

mine roof and the top level of the cured ribfill are evident where coal mines with the following restrictions. These seal designs 

incomplete closure was obtained during the initial grout injection as constructed and tested in the LLEM cannot be used in entries 

process. 
spontaneous combustion within the sealed area. The over

pressures generated from the methane ignition resulted in the 

failure of several seals that were newly installed about 22 hr 

before the ignition. As a result of this disaster, a considerable 

public outcry demanded that an in-depth inquiry be conducted 

to determine the cause of the explosion and to recommend ways 

to prevent future occurrences in the Queensland coal mines. 

In late 1997 and early 1998, PRL collaborated on a joint 

research project with Barclay Mowlem Construction Ltd. of 

Queensland, Australia, to investigate the capability of various 

seal and stopping designs and an overcast design to meet or 

exceed the requirements of the Queensland Department of 

Mines and Energy's [I9961 Approved Standard for Ventilation 

Control Devices. This standard was the result of deliberations 

and investigations by Task Group 5, which was formed by the 

recommendation of the Warden's Inquiry concerning the Moura 

No. 2 mine explosion [Roxborough 19971. Task Group 5 was 

charged with the reassessment of the regulatory provisions for 

explosion-resistant seals and the investigation of mine inerting 

techniques. Similar to an evaluation program done in 1997 with 

Tecrete Industries Pty. Ltd. of New South Wales, Australia 

[Weiss et al. 19991, this evaluation program with Barclay 

Mowlem Construction Ltd. at the LLEM tested designs within 

a range of overpressures to match the recommendations of Task 

Group 5. The overpressure ratings for underground ventilation 

agg o.to .8 g. e geooad bee

enlarged previously, forming a roadway with dimensions that 

are representative of those found in Australian underground 

coal mines and some U.S. coal mines. As with the previous 

Australian program, one particular requirement of the Barclay 

Mowlem program was to test an isolating seal design that 

could withstand an explosion producing a static horizontal 

overpressure of -140 kPa within 24 hr of its completion. 

Additionally, this Barclay Mowlem program was the first time 

that an overcast design had ever been evaluated for strength 

characteristics and air leakage resistance when subjected to fullscale explosion overpressures. 

CONSTRUCTION OF SEALS, STOPPINGS, 

AND OVERCAST 

Several Barclay Mowlem seal and stopping designs and an 

overcast design, using specially designed reinforced vinyl 

bladders in-filled with cementitious grout, were tested in the 

LLEM. There were two parts to the testing program. The first 

part involved building and testing two seal designs at explosion 

overpressures of r 140 kPa (20psi). Two stopping designs were 

also evaluated at explosion overpressures of 14-19 kPa (2-3 psi). 

The second part of the program was the testing of an overcast 

design and two additional seal designs. 
The Barclay Mowlem seal and overcast designs all used 

a vinyl bladder system suspended by a metal framework 

anchored to the mine roof. The bladders were made with a 

double-sided white polymeric coated polyester fabric 

(VYNA 5 16, manufactured by Southcorp Industrial Textiles, 

Clayton, Victoria, Australia) with antistatic and fire-retardant 

characteristics. The various vinyl bladder configurations are 

discussed in the next section on "Seals." These vinyl bladders 

were preinflated with air before the grout-filling process. The 

portland cement-based grout, B M Mine Grout, was made in 

Australia by Blue Circle Southern Cement Ltd., Greystances, 

New South Wales, Australia. Compressive strength tests on the 

grout as conducted by Blue Circle Packaging in Australia 

provided the following results: 10 MPa (1,450 psi) at 1 day, 

18 MPa (2,610 psi) at 2 days, 48 MPa (6,960 psi) at 7 days, and 

68 MPa (9,860 psi) at 28 days. The grout was pumped into the 

suspended, preinflated vinyl bladders using a GP 2000 pump. 

This is a compressed air-driven modular unit that encompasses 

a mixing bowl mounted over a receiver hopper that has a screw 

feed to a small positive displacement pump. The prebagged dry 

grout mix was combined with a measured amount of water to 

achieve the correct material strength characteristics and then 

pneumatically pumped through a 50-rnrn-diam hose into the 

vinyl bladder. Shotcrete operations used the same prebagged 

shotcrete grout mix that was used inside the vinyl bladders of the 

seals and overcast. The shotcrete was spray applied using a 

Meyro Piccola machine. This shotcrete machine pneumatically 

delivers the dry shotcrete to a mixing nozzle where an operator 

can adjust the volume of water to achieve the desired consistency of the material applied. When handling these 

cementitious products, all safety data sheet instructions should 

be adhered to by the operators. 

A summary of the construction data for the four seals, two 

stoppings, and overcast is found in tables 3 and 4. The grout 

injection dates and final shotcreting dates are listed in table 3. 

The last column of table 3 shows the LLEM explosion test after 

whch the stopping or seal was removed. The dimensions of the 

stoppings and seals are listed in table 4. Additional construction 

details for the seals, stoppings, and overcast are found in the 

next three sections of this report. The designs were built in 

the LLEM under conditions similar to those that may be 

encountered during seal construction in an underground coal 

mine. As in the installation of any seal, all loose material had 

to be removed fromthe seal construction site, leaving competent 

strata. It must be noted that the test environment at the 

LLEM is one of solid, nonyielding strata. Previous practice 

during some seal evaluations in the LLEM was to provide edge 

restraint by bolting 150-mm by 150-mm steel angle (12 mm 

thick) to the floor and ribs. These steel angles were attached 

using 600-rnm-long, 25-mm-diam grade 8 steel all-thread rod 

(embedded 450 mm) or 230-mm-long, 25-mm-diam Hilti Kwik 

bolt fasteners as manufactured by Hilti, Inc., of Tulsa, OK. 

Both rods and bolts used 450-mm spacings on the floor and rib. 

Several U.S. operating coal mines have been permitted to use a 

similar type of edge restraint in areas with hard sandstone floors 

in which standard keying would be very difficult. To acheve 

the desired hitching (recessing) for this program, the concrete 

floor was trenched to a depth of either 150 or 300 mm (6 or 

12 in) and/or the 150-mm (6-in) steel angle was used. The 

hitching on the ribs was simulated by bolting the 150-mm by 

150-rrm by 12-mm-thick steel angle to each of the ribs on either 

side of the structure. The 25-mm-diam steel bolts were fullresin anchored and embedded 900 mm into the ribs on 

appro:uimately 450-mm centers. 

The mine air temperature during the 3-month construction 

and testing period ranged from 8 OC to 19 OC (47 OF to 66 OF) 

and averaged 1 1.5 OC (52.5 OF). The relative humidity ranged 

from 52% to 76.5% and averaged 66%. Heaters were used in 

the immediate vicinity of the seal and overcast locations to raise 

the mine temperature during the grouting operations. The grout 

used in this program was formulated for use in Australian coal 

mines, which are typically 5 OC to 10 OC (10 OF to 20 OF) 

warmer than U.S. mines. Initial compressive strength test results 

from the grout samples taken during the construction of the first 

seal showed that the cooler temperature of the LLEM slowed the 

cure tiime of this grout, thereby affecting the short-term strength 

characteristics of the grout, i.e., the compressive strengths of the 

grout samples as cured in the LLEM were typically lower 

for a given cure period compared with those obtained from 

samples taken in the warmer Australian mines. Given the time 

constraints of the program, the heaters were used to compensate 

for the cooler mine temperatures and allowed the grout to cure 

in temperatures typical of Australian coal mines. 

Seals 

During this Barclay Mowlem program, the seals were built 

with a cementitious-based grout with polyfibers. The grout was 

pumped into a vinyl bladder assembly. The vinyl bladder used 

for th~e first two seal designs and the overcast wall designs 

consisted of a series of interlocking tubes joined together by 

baffles (figure 11). The baffles provide a means to allow the 

grout to flow through the interlocked vinyl tubes. This results 

in a wziform distribution of the grout throughout the entire width 

of the seal. Two 25-mm-diam valves (shown as "bleeder ports" 

in figure 1 1A) are attached to the bladder as a means to inflate 

air before the grout injection process and for subsequent air 

release during the grout injection process. Two 50-mm-diam 

valves are attached to the bladder for the grout injection. 

At the start of the seal installation, a spreader bar, which is 

built from 50-mm by 50-mm medium gauge tubing spaced 

300 nlrn apart, is attached to the mine roof. During installation, 

the spreader bar assembly is held in position by roof jacks 

(figure 12). A flat metal strap is placed over the spreader bars 

and then bolted to the mine roof using 900-mm-long by 25-mmdiam fully encapsulated resin roof bolts on 2-m spacings. After 

the spreader bar assembly is installed, the roof jacks are 

removed and shotcrete is applied to the spreader bar assembly 

(figure 13). The vinyl bladder is pulled into place by ropes 

attached to a series of hooks on the spreader bar (figures 13- 14) 

and then inflated. Between each of the Inflated large vinyl 

bladdier tubes are smaller 100-mm-diam piers (see figure 1 1 A) 
Figure 12.--Spreader bar anchored to the mine roof used to 

support the seal bladder system. 

that are interlocked to the outside and overlapped under the 

main bladder assembly. The piers are made from the same vinyl 

fabric as the bladder. For additional reinforcement, a light chain 

is attached to the spreader bar hooks and then dropped into each 

pier. At the bottom, the chains from the piers on either side of 

the seal are tucked under the main vinyl bladder. Figure 14 

shows the vinyl bag attached to the spreader bars, with an 

additional person holding one of the injection ports. 

Figure 14.-Inflated vinyl bladder assembly showing the 

injection port for the piers. 

Variations occurred during the installation of the seals in the 

LLEM compared to the standard installation in an Australian 

coal mine. Ths was due, in part, to the solid limestone strata, 

the concrete floor, and the- entry geometry in the LLEM; 

Recessing of the seal into the roof and ribs was simulated using 

the 150-mm by 150-mrn by 12-mm-thick black steel angle 

(standard coal mine installation would require recessing to 

300 mm). Recessing of the seals into the floor was by a 

combination of trenching and/or steel angle. The concrete floor 

of the LLEM was trenched to a depth of 300 mm for the first 

two seal designs (installed in crosscuts 2 and 3); this was similar 

to the requirement for a standard seal installation in a coal mine. 

Steel angle was also used on the floor on the B-drift side of the 

crosscut 2 seal, providing an equivalent hitching depth of 
described in the above paragraphs (see figures 15 17). The 

450-mm-thick seal in the 2.8-m-high roof section of crosscut 3 

was also built (figures 18-19) in a similar manner, except that 

the spreader bar was not recessed into the mine roof. Samples 

were taken during the grout injection process for compressive 

strength analyses at an independent lab. The compressive 

strength of the grout samples averaged 2.4 MPa (350 psi) after 

Figure 15.- Framework for construction of seal in crosscut 2. 

Figure 16.--Construction of seal in crosscut 2 showing vinyl I 

bladder in place, but not yet filled. Figure 17.--Completed seal in crosscut 2. 
Figure 18.--Construction of seal in high roof section of 

crosscut 3, showing the vinyl bladder being installed. 

Figure 20.--Construction of seal in crosscut 4 showing the 

vinyl tubes before filling. 

Figure 19.-Construction of seal in high roof section of Figure 21.-Construction of second seal in high roof section 

crosscut 3, showing the grout injection hose attached to the d crosscut 3. 

bladder. 
side. A 25

rnmthick coating of shotcrete was sprayed on the 

entire face and perimeter of the C-drift side (explosion side) of 

each seal. Shotcrete was then sprayed on the back (B-drift side) 

perimeter of each seal. 

Figure 22.--Construction of seal in crosscut 4 showing details 

of the tops of the vinyl tubes and light meshing overlay. 

stone dust in order to conform to the irregularities of the mine 

Figure 23.--Construction of water stopping in crosscut 3, with 

the individual tubes suspended from the roof-mounted spreader 

bar. 
simulate a 150-mm recess on the C-drift ribs and floor. The 

contour of the mine roof and ribs on the B-drift side of the 

quickseal location provided recessing >I50 mm. The bladder 

of the quickseal was not attached to the mine roof and was only 

held into position by the frictional forces exerted on the mine 

strata due to the internal pressure of the inflated bladder. No 

shotcrete was used. 

Figure 24.-Details of the Velcro and plastic clip fastening 

system for the water stopping in crosscut 3. 

w. PERSPECTIVE VlEW 

6. SIDE WW =& 

C. TOP VlEW OF DECK 

Figure 25.--Schematic drawing of overcast at the intersection 

of Bdrift and crosscut 3. A, perspective view; B, side wall 

showing instrumentation positions, as viewed from Bdrift outby; 

C. top view of deck showing instrumentation positions. 
was that a short extension wall was required to be built at each 

end of both side walls in order to extend the side walls to and 

beyond the intersection corners (and away from the electrical 

and water connections embedded in the LLEM ribs). These 

extension walls are not shown in the figure 25 schematic, but 

(figure 30). Grout was pumped into the top deck form, filling it 

to the top of the metal skirt. After the grout had set, 900-mmlong by 25-mm-diam full-resin bolts were installed on 1.5-m 

spacings down through the 200-mm-thick top deck slab and into 

the top edge of the side wall. 

Figure 26.4onstruction of side wall of overcast at the Figure 27.4onstruction of overcast at the intersection of Bintersection of 6-drift and crosscut 3. drift and crosscut 3: installation of deck on top of side wall. 
Figure 29.-Top view of overcast deck showing reinforcing 

bars. 

The two wing walls sit on the edges of the top deck parallei 

to B-drift (figure 25) and seal the area between the top deck 

and the overhanging roof line. In the LLEM installation, the 

wing walls seal the void space above the top deck toward A- and 

C-drifts in crosscut 3, thereby forcing the ventilating air to flow 

under the overcast deck in the crosscut and above the deck in 

B-drift. Vinyl straps attached to the top of the vinyl bladders 

(wing wall grout fonns) are tied to 150-mm-long by 25-mmdiam Hilti Dyna bolts anchored in the mine roof. No spreader 

bars, piers, or chains are used for the top wing walls. The grout 

is pumped into the inflated vinyl wing wall bladders in the same 

manner as the side walls, with all ofthe air and water completely 

bled from the bladder as the grout fills the bladder. Figure 3 1 is 

a side view of the installation of a wing wall. Figure 32 is an 

underneath the deck. Three steel angle braces were anchored to 

the outside of each of the IMQ overcast s~de walls and to ti)!: 

concrete mne floor using the IIlltl Dyna bolts. ?'he use oi'thc.>c. 

angle braces is not standard ~nstallat~on practice; they uesc uhcd 

in the ILEM evaluat~oni since the side walls could not be 

directly rccessed lnto the nllile rlbs because of the larger six 01' 

tile intersectior,. 1% final coating of shotcrete was applied to thc 

entire overcast structure to seal the wlng wall structures to the 

mine strata and to seal aii bolted areas. 

Instlumentation was then placed on the s~de ualis, deck, an3 

wing walls of the co~npleted overcast. Steel angle frames west 

erected beside the outb). side wall ir, U-drift to suppon t11c 

instrumentation boxes and LVDTs, as shown in figure 34. ( )ne 

I.VDT was placed at the center of the side wall, one at quarter-. 

height and midwidth, one at three-quartcrs height and midwidth. 

and one at midheight at one-quarter of the way from thc side 

(figures 255 and 34). This was the same positioning uscd for 

the L.VDTs on the seals. The LVDTs on the deck were 

suspended from the roof by steel frames (figure 35). A detail of 

the LVDT attached to the top of the deck is shown in figure 36. 

.4 top view of the deck showing LVDT positions is shown in 

figure 25C. One LVD?. was also positioned at the rniddle of the 

wing wall facing C-drift. 
Fiaure 35.-Instrumentation on to~ of overcast deck: three 

Figure 32.4onstruction of wing wall along edge of overcast LVDTS-suspended above deck. 

deck: end view of wing wall above deck. 

Figure 33.--Completed overcast viewed from under the deck. 

Figure 36.41oseup of LVDT suspended 

from roof and attached to deck. 
differentials up to 1 kPa. The water

filled tube stopping showed 

significant air leakage up to 0.55-kPa pressure differential. At 

1 -kPa pressure differential, the water tubes separated from 

the bottom support (figure 38). Note that this stopping was 

designed to release in this manner during low-level explosion 

pressures. These water-filled tubes were reattached to the 

stopping base and shotcrete was reapplied. The air leakage 

through this stopping was then remeasured before the first 

explosion test. as listed in table A-5. The air-inflated vinvl 

Figure 38.-Release of individual water tubes of stopping during air leakage test. 

Figure 37.--Completed water stopping in crosscut 3. Fi~ure 39.-Air-inflated vinyl bladder of quickseal in crosscut 4. 
seal designs against higher impulse loadings. The calculated 

pressure-time integral for either static or total pressure for the 

seal in crosscut 2 was about 9 Wa-s, giving a total impulse of 

1 10 kN-s. 

Postexplosion observations showed, as expected, no 

structural damage to the seal in crosscut 2. However, a portion 

of the shotcrete coating had been removed by the explosion, 

exposing some of the vinyl bladder. The water-filled tube 

stopping in crosscut 3 withstood the explosion pressure 

(figure 40). The individual water tubes released, water was 

dispersed throughout the area, and the pressure was successfully 

vented as designed. However, all except two of the water tubes 

unexpectedly ruptured along each bottom tube seam, resulting 

in a complete loss of water from each tube. Under ideal 

performance, about one-half of the water would have remained 

in each tube after the explosion. The tubes, although emptied of 

water, performed as expected and restored partial ventilation. 

The quickseal air-inflated vinyl bladder in crosscut 4, although 

dislodged, withstood the low-level explosion without rupturing. 

Because of a programchange, the standard anchoring techmques 

to the mine strata and the remote deployment method were not 

~mplemente~ with the quickseal design as originally planned. 

Figure 40.--Condition of water stopping in crosscut 3 after test 

358. 

Postexplosion air leakage tests were not Grfo-d against Figure 41.--Completed seal in the high roof section of crossthe water stopping or the quickseal air-inflated bladder since cut 3. 
10.7 rnrn for the LVDT at the right

side position (farthest outby) 

on the back of the seal. The movement at the middle position on 

this seal was 5.6 mrn. The greatest movement for seal 3 was 

4.5 rnrn for the LVDT at the right-side position. The movement 

at the middle position on this seal was 2.0 mm. Subsequent air 

leakage tests (table A-7) provided marginal results compared to 

the established U.S. guidelines. The crosscut 2 seal exceeded 

the leakage guidelines for all pressure differentials >0.25 Wa, 

and the crosscut 3 seal in the high roof area exceeded the 

guidelines for a pressure differential >0.75 kPa. Smoke tube 

evaluations revealed the location of the main air leaks for both 

seals. One air leak was at the grout injection port on the 

crosscut 2 seal; the other leaks were along the riblines behind 

the steel strapping on both seals. This may not pose a significant problem in an actual coal mine installation since the 

seals will be recessed into the ribs with subsequent shotcrete 

coatings. 

Third Explosion Test (LLEM Test 360) 

On March 3, 1998, a third explosion test was done to subject 

the two similar seal designs to an explosion overpressure 

>345 kPa (50 psi). The seals would be rated as "type D" based 

on the Queensland Department of Mines and Energy's Approved 

Standard for Ventilation Control Devices if they successfully 

0 1 2 3 4 5 

TIME AFTER IGNITION, s 

Figure 42.-Pressure traces as a function of distance from the 

closed end (face) in Cdrift for test 359. 

Figure 43.-Seal in crosscut 2 after test 359. 
pypg

??!;-kl'a (54-psi) static pressure and a 380-kPa (55-psi) "total" 

pressure agalnst the scal in crosscut 2 (table B-5). However, for 

the sea: in crosscut 7. the peak static pressure was 475 Wa 

(09 psi) and the "total" pressure was 545 kPa (79 psi). This 

variation in pressure on the two seals was probably due to 

prcTsure piling as the explosion traveled through the coal dust 

z:)ne. l3ased on the very limited number of explosion tests in the 

LLEM that generated peak pressures >250 kPa, no guarantee 

could he provided during this program on the ability to achieve 

a uniform -73.5 -kPa pressure pulse throughout the seal test zone. 

Future studies may attcnlpt to better achieve this goal through 

experimentation, such as varying the coal dust loading through 

the zone. 

Postexplos~on observations showed that thc seal in crosscut 2 

survived the 370-kPa static overpressure with only minor 

damage to the surface shotcrete coatings (figure 45). Subsequent air leakage evaluations for this seal (table A-8) showed 

that the leakage rates were at or slightly above the established 

air leakage guidelines. An interesting result of this test was that 

the postexplosion air leakage for seal 2 (table A-8) was lower 

than the preexplosion leakage (table A-7). For example, the 

postexplosion air leakage was 32% lower at 1-kPa pressure 

differential. One potential explanation for this phenomenon is 

that if a seal is not significantly damaged during an explosion, 

pppg, 

LVDTs at the middle and bottom positions on the seal are 

shown. They show the seal being displaced by the pressure 

pulse and then returning to its original position as the pressure 

decays,. The maximum displacements for all of the LVDTs on 

this seal are listed in table D-3. The greatest seal movement was 

1 2.2 mm for the LVDT at the right-side position (farthest outby) 

on the 'back of the seal. The movement at the middle position on 

the seal was 5.6 rnrn. 

The seal in the high roof area of crosscut 3 was destroyed by 

the 475-Wa (69-psi) static pressure pulse (figure 47). From 

postexl~losion observation of the seal, it seemed that the seal 

failure started at the top of the seal, where only a minimum of 

hitching was achieved due to the contour of the hard limestone 

mine roof. Figure 48 shows the static pressure data from the 

two transducers on either side (71 and 93 m) of the seal in 

crosscut 3 compared to the total pressure data from the 

transducer in front of the seal (75 m). As in figure 46, the time 

scales of the two static pressure traces were shifted so that the 

peaks matched with that of the transducer at the seal. In the 

upper part of figure 48 are the traces from the LVDTs at the 

middle and bottom positions on the seal. The maximum 

displacements for all of the LVDTs on this seal up to the tlme of 

seal failure are listed in table D-3. The greatest seal movement 

was -30 rnm at three of the LVDTs. The times of seal failure 
Figure 47.-Remains of crosscut 3 seal after test 360. 

can be determined fiom the LVDT traces. For LLEM test 360, 

the LVDTs were set at an initial position corresponding to about 

-5 V. This would allow them to measure a large signal up to 

about +10 V, or a total movement of about 45 mrn. The sudden 

drop in the LVDT signals and return to -0 V (-15 mrn) in 

figure 48 signifies that the seal failed and the LVDTs were 

destroyed. Failure occurred at -0.84 s for the bottom LVDT 

and at -0.89 s for the middle LVDT. The LVDT traces for the 

seal in crosscut 3 do not gradually return to their original 

positions as they did for the seal in crosscut 2 (figure 46). The 

rubble from the destroyed seal in crosscut 3 was removed before 

the next series of tests against the overcast. 

intersection of crosscut 3 and B-drift during March 7-24, 1998. 

The explosions originated at the face of C-drift, and the 

pressures traveled down C-drift and then through crosscut 3 to 

the underside of the overcast (figure 25). The fourth explosion 

test (L.LEM test 361) on March 26, the fifth test (LLEM test 

362) on March 31, and the sixth test (LLEM test 363) on 

April 11, 1998, were designed to generate overpressures ranging 

from about 15 kPa to 50 Ha at the overcast location. This is 

the fir!jt time that an overcast design has ever been explosion 

tested under full-scale conditions. Before conducting the first 

explosion test against the overcast design, an air leakage test 

(table ,443) was done. To accomplish the air leakage test on the 

overcast, both B- and C-drifts were sealed outby the overcast 

location using brattice curtain attached to a wooden framework 

custom-fit to the entry. In addition, the crosscut between A- and 

B-drifts in crosscut 3 was sealed, as was B-drift inby the 

overcast location. The pressure differential under (or through) 

the overcast increased as the ventilation fan speed increased. 

Any air leakage through the overcast deck, side walls, or 

wing walls was detected through the 465-cm2 center opening in 

the B-drift inby curtain. The air leakage rates through the 

overcast design (table A-8) were well within the air leakage 

guidelines established for seal designs. The overcast withstood 

the 16-, 30-, and 47-kPa explosion overpressures generated 

during tests 36 1,362, and 363, respectively (see tables 1,5, and 
B-6 to B-8). These pressures were measured by a transducer 

located in the inby rib of croescut 3. Therefore, they are the 

static pressures that would be exerted on the inner sides of 

the side walls and the underside of the deck of the overcast. 

Cracking of the cementitious top deck became more pronounced 

after each of the three explosion tests and was a result of 

the upward pressure exerted on the deck as the explosion 

pressure vented through the overcast. However, the leakage 

rates (table A-9) through the overcast after the 16-kPa (2.3-psi) 

explosion test 361 were still well within the established 

guidelines. After this leakage test, shotcrete was reapplied to 

the overcast on all visible cracks. These cracks were mainly on 

the overcast deck and the interface of the deck with the side 

walls and wing walls. The leakage rates fiom a subsequent air 

leakage test showed only nominal improvements compared to 

those of the first test. No further air leakage tests were done for 

the overcast design after LLEM test 361. The LVDT data for 

the overcast tests are listed in tables D-4 through D-6. The data 

show almost no movement (<I mm) of the side wall in any of 

the tests. The LVDT on the wing wall recorded a maximum 

movement of 2.6 mm during LLEM test 363. The maximum 

upward movements of the deck in LLEM tests 361, 362, and 

363 were 5.5, 14.5, and 16.4 mm, respectively. The LVDTs 

located off-center on the deck usually recorded smaller 

movements than the middle LVDT. The upward movements of 

the deck were followed by maximum downward rebound 

movements of 1.4, 15.7, and 15.7 mm in LLEM tests 361,362, 

and 363, respectively. Examples of the LVDT traces for the 

overcast are compared to the pressure trace for LLEM test 363 

in figure 49. The static pressure was measured at the inby 

crosscut rib leading from C-drift to the underside of the 

overcast. The LVDT traces include the one on the wing wall, 

two on the deck, and the middle one on the side wall (see 

table D-6 for summary data and figure 25 for locations). In 

figure 49, positive deflection on the wing wall is toward C-drift. 

On the deck, positive deflection is upward; on the side wall, 

positive deflection is outby. 

Seventh Explosion Test (LLEM Test 364) 

The seventh and final explosion test of this program was 

done on April 3, 1998, to evaluate the capability of two 

additional seal designs to withstand a pressure pulse of at least 

140 kPa. This test also provided additional evaluation of the 

overcast. The test setup was similar to that of the second 

explosion test (LLEM test 359) in terms ofgas ignition zone and 

coal dust loading on each shelf, except that only two shelves 

were used instead of four. The resultant explosion generated an 

explosion overpressure that averaged 160 kPa (23 psi) through 

the seal test area. Detailed data on the pressures at various 

distances down the entry and at the seals are listed in the 

table B-9. The flame speed averaged 340 mls for this test. 

The 240-mm-thick seal in crosscut 3 consisted of individual 

bladder tubes attached to a single vinyl unit. This unit was 

suspended using chains from the steel framework bolted to the 

mine roof. This chain was also installed into each of the bladder 

J 1 I 

LVDT, wing wall 

I 

L 

I I b 

I I 

LVDT, side wall - -3 

- 

I I L 

0 1 2 3 

TIME, s 

Figure 49.-Pressure and LVDT traces for overcast 

cluring LLEM test 363. 

tube!; before the grout injection into the tubes. The back side of 

the completed seal is shown in figure 50, with one LVDT in the 

center of the seal. The seal in crosscut 4 (figure 51) was very 

sirnil.ar in design, but used 165-mm-diam tubes. This smaller 

seal design was installed in crosscut 4 before the low-level 

explosion tests against the overcast design to allow for a longer 

cure period for the grout. The new 240-mm-thick seal in the 

high roof section of crosscut 3 was installed after the overcast 

evaluation tests. This seal was explosion tested about 24 hr after 

its completion. 

Before this seventh and final explosion test of the Barclay 

Mov~rlem program, shotcrete was reapplied to seal 2. The seals 
Figure 51.--Completed new seal in crosscut 4. 

were then leakage tested (table A- 10). No air leakage could be 

detected through any of the three seals at pressure differentials 

up to 0.34 kPa For pressure differentials of 0.55 and 1.06 kPa, 

only minor leakages were measured, but they fell well within the 

established guidelines for these seal evaluation programs. The 

data in table A- 10 for seal 2 show that the additional shotcrete 

significantly reduced the air leakage from the values measured 

earlier (see table A-8). 

The ignition of the gas zone and subsequent burning of the 

coal dust generated pressures of 195 kPa (28 psi) at the 

450-mm-thick seal in crosscut 2, 160 kPa (23 psi) at the 

240-mm-thick seal in the high roof area of crosscut 3, and 

115 kPa (1 7 psi) at the 165-mm-thick seal in crosscut 4. Both 

new seals in crosscuts 3 and 4 were destroyed by the explosion. 

As figure 52 shows, the individual grout columns of the 

165-m-thick seal in crosscut 4 were apparently not thick 

enough to withstand the explosion pressure pulse, which resulted in nearly complete destruction. Except for a few of the 

thick seal in crosscut 2 survived this explosion as it had the 

previous ones. As shown in table A-l 1, the postexplosion air 

leakage rates for this seal were well within the acceptable 

guideljnes. 

It was originally anticipated by Barclay Mowlem that the 

seal in crosscut 3 and probably the seal in crosscut 4 would 

survive this explosion, and therefore the pressure pulse would 

continue outby in C-drift until it reached the next open crosscut 

(crosscut 5). It would then vent through the crosscut and travel 

back inby in B-drift. The pressure pulse would then pass over 

the overcast (figure 25) and exert a downward pressure load on 

the overcast deck. Therefore, before the test, the LVDTs were 

moved from positions on the outby face of the side wall and the 

top of the deck to positions under the overcast. One LVDT was 

positior~ed underneath the deck in the middle of the deck, and a 

second LVDT was positioned halfway between the middle and 

the C-dnft edge of the deck. No LVDTs were placed on the side 

wall. Pw a result of the failure of the seal in crosscut 3, the 

pressure pulse traveled down crosscut 3 and the overcast was 

subjected to an overpressure of 4 1 kPa (6 psi) under the overcast 

deck. The maximum upward movement of the overcast deck 

during ,this test was 15.8 mrn; the details on the other 

measurements are in table D-8. This upward deflection was 

comparable to that observed in LLEM test 363, whch had a 
slightly higher pressure underneath the overcast. Because the the later downward rebound before being destroyed. The LVDT 

pressure pulse came under the deck rather than above as toward C-drift may have been destroyed before recording the 

originally expected, the two LVDTs were tom from their downward rebound. The overcast itself survived explosion test 

supports during the test. However, the middle LVDT on the 364, a!; it had test 363. 

deck was able to record both the initial upward deflection and 

PRELOADED SOLID-CONCRETE-BLOCK SEAL DESIGNS 

FOR FRIABLE RIB CONDITIONS 

In 1998, PRL and MSHA jointly participated in a research 

program to evaluate the strength characteristics and air leakage 

resistance of preloaded solid-concrete-block seals for use in 

underground coal mines. These seals were specifically designed 

for use in areas of mines where the standard method of hitching 

or keying of the concrete block seal into the mine ribs was 

impractical due to the weak coal (i.e., fhable ribs). These seals 

were jointly designed by personnel from the United Mine 

Workers of America (UMWA) at Jim Walter Resources, Inc.'s 

Blue Creek No. 5 Mine; Strata Products, Inc.; and Jim Walter 

Resources, Inc., in Alabama. Assistance was provided by 

MSHA and PRL personnel. 

Installation ofthe standard solid-block seal requires floor and 

rib htching to meet the intended explosion pressure resistance 

of 138 kPa (20 psi). Standard seal strength is due to an arching 

action that occurs through the thickness of the seal, which 

applies lateral thrust to the coal ribs, floor, and roof. Jim Walter 

Resources, Inc.'s No. 5 Mine encountered extremely soft and 

fhable ribs conditions, malung conventional rib hitching of the 

standard seal almost impossible. The coal was so soft that large 

sections of the rib coal can be removed by hand, making it very 

difficult to interface with competent coal. Injection grouting to 

strengthen the ribs was not considered economically feasible. 

The alternative seal designs tested under this program were 

based on better coupling between the seal and the mine roof and 

ribs by preloading the seal with pressurized grout bags. These 

pliable fiberglass Packsetter bags were placed along the 

perimeter of the seal and pressurized with a cementitious grout. 

CONSTRUCTION 

Three solid-concrete-block seals were installed in the LLEM 

(tables 3 and 4). The seals were very similar to the standardtype solid-concrete-block design described in the CFR. Each 

seal used solid concrete block with nominal size of 20 cm by 

20 cm by 40 cm (8 in by 8 in by 16 in). These were tongue-andgroove solid blocks supplied by Willcut Block & Supply Co., 

Inc., of Tuscaloosa, AL. Based on a random sampling, the 

average weight per block was 26.4 kg. Two of the three seals 

used hlly mortared joints (seals in crosscuts 2 and 3); one seal 

used only dry-stacked blocks (seal in crosscut 4). The Quikrete 

portland cement mortar was from Independent Cement Corp., 

Hagerstown, MD. This mortar exceeds the compressive strength 

requirements of ASTM C-387 and ASTM C270, type N. For 

each seal, the vertical block joints between courses were 

staggered, the main seal wall was 405 mm thick, and an 

interlocked 8 1 -cm by 40-cm center pilaster was used. The seals 

did noit use any rib hitching. Floor hitching was used to augment 

the strength of one seal (crosscut 2); no floor hitching was used 

for the other two seals. The floor hitching for the seal in 

crosscut 2 was simulated by anchoring 15-cm by 15-cm by 

13-mnn-thick steel angle to the mine's concrete floor in a 

position abutting the lower course of concrete block. The steel 

angle was anchored to the floor using 25-mm-diam by 230-mmlong E[ilti Kwik Bolts I1 on 46-cm centers. Any gaps between 

the steel angle and the seal were filled with mortar. The 

mortared block seals in crosscuts 2 and 3 required 276 and 300 

concre:te blocks, respectively. The dry-stacked design in 

crosscut 4 required 355 blocks. For the seals in crosscuts 2 

and 3, half-size concrete block (10-cm by 20-cm by 40-cm) 

were used to minimize the gap near the mine roof. 

The main difference between these concrete block seals and 

the design described in the CFR is the use of pliable bags 

pressurized with cementitious grout on the mine ribs and roof in 

place of conventional hitching. These pressurized bags are 

referred to as "Packsetter bags." The Packsetter grout bags, 

manufactured by Strata Products, Inc., Marietta, GA, have a 

130-cln by 80-cm outer shell of plastic weave with a 122-cm by 

76-cm inner plastic bladder. The Packsetter bags have a oneway valve constructed in the filling port. This valves permits 

the flow of grout into the bag and closes to prevent the grout 

from flowing back out of the bag. The Packsetter bags are 

positioned at the interface between the seal and the roof and ribs 

(figure 53) and then filled with grout (figure 54). For the seals 

in crosscuts 2 and 3, 1 1 full-size and 1 half-size Packsetter bag 

(figure 54) were required along the seals' interfaces to the mine 

roof and ribs. For the dry-stacked seal in crosscut 4,10 full-size 

and 10 half-size Packsetter bags were used. For this seal, the 

interface with the mine roof used a combination of full- and 

half-sized bags. The bags were overlapped a minimum of 

15 cm. The distance between the mine rib and block should be 

<2-5 cm. During the LLEM evaluations, the blocks were 

installed tight against the bag and rib (figure 55). The gaps 

between the top block course and mine roof ranged from 5 to 

12 cm. 

To facilitate the construction process, the grout was injected 

into the Packsetter bags using the mine's compressed air to 

power the grout pump. As an alternative method for filling the 

bags where a compressed air supply may not be available, a few 

of the Packsetter bags during this construction process were 
show1 in figures 57-58. Upon completion of the Packsetter 

seals, sealant was applied to selected perimeter areas on both 

sides of the seals in crosscuts 2 and 3. The sealant was applied 

Figure 54.-Filled and pressurized Packsetter bags at the outby 

roof and rib seal interface showing full-size bags and one half-size 

bag on the left. 

Figure 55.-Placement of the Packsetter bag at the 

mine rib and floor interface with the bottom course of the 

tongue-andgroove solidconcrete-block seal. 

Figure 56.-Hand-powered pump for filling the 

Packsetter bags. 
increase the static pressure levels during this second test. 

14.5 lrg of pulverized coal dust was loaded onto shelving that 

was suspended from the mine roofjust outby the gas zone from 

Figure 57.--Completed mortared seal with the Packsetter bags 13 to 23 m from the face. The nominal coal concentration of 

and floor hitching in crosscut 2. this -12-m-long dusted zone was -100 g/m3. The resultant 

explosion generated a static pressure pulse of 185 Wa (27 psi) 

at the crosscut 2 seal, 155 kPa (22 psi) at the crosscut 3 seal, and 

125 kPa (18 psi) at the crosscut 4 seal (see tables 5 and B-11). 

The rnortared block seal with the Packsetter bags and floor 

hitching in crosscut 2 survived the explosion wlth no evidence 

of outward damage (figure 59). The mortared block design wlth 

the Packsetter bags but without the floor hitching in crosscut 3 

showed a slight movement at the mine floor, as evidenced by the 

separation of the sealant applied to the blocWfloor interface 

(figure 60). Three vertical hairline cracks were evident on the 

B-drift (nonexplosion) side of the seal between the center 

pilaster and the outby rib. Portions of the perimeter sealant on 

each side of the seal were also dislodged during the explosion. 

The dry-stacked block design with the Packsetter bags was 

dest~oyed by the explosion. Only the bottom course of block, 

which was mortared to the mine floor for leveling purposes, and 

Figure 58.--Completed mortared seal with the Packsetter bags Parts of the seal near the mine ribs remained (figure 61). 

in crosscut 3. 
As alternative ventilation structure designs andlor construction materials are introduced to the mining industry 

to address the wide range of geologic, geometric, and environmental conditions encountered in underground coal mines, 

evaluations of these seal designs and materials must be done to 

ensure that the designs perform the intended function and that 

they provide the required protection to underground personnel, 

as described in 30 CFR 75.335, prior to use in mines. Testing 

the strength characteristics of these ventilation structures against 

methane ignitions and/or coal dust explosions and measuring the 

air leakages in the full-scale LLEM is one accepted method. 

This report describes several unique and innovative seal, 

stopping, and overcast designs that were evaluated in three 

programs during 1997-98. 

In the first program, several pumpable cementitious plug 

seals that do not require floor or rib hitching were subjected to 

a minimum static pressure pulse of 138 kPa (20 psi) and were 

shown to meet or exceed the strength requirements mandated 

by the CFR while maintaining acceptable air leakage rates. 

These designs were developed by HeiTech, a U.S. seal 

manufacturer that hnded the program. These included a 

6 10-mm-thick seal using a pumpable cementitious grout with an 

average compressive strength of 4.7 MPa, a 760-mm-thick seal 

with an average grout compressive strength of 3.3 MPa, and a 

915-~rnrn-thick seal with an average grout compressive strength 

of 3.10 MPa. Before this program, any pumpable cementitious 

plug seal used in an underground coal mine needed to be at least 

1.2 nn thick with a minimum compressive strength of 1.4 MPa. 

It wa!s also shown, by the removal of the form wall before the 

secoind explosion test in this program, that the form walls used 

to contain the cementitious grout slurry need not be considered 

as part of the seal design. However, if these form walls are 

removed, the exposed cementitious grout must be coated with an 

approved MSHA sealant. 

In the second program, four reinforced cementitious seals and 

two stopping designs (tables 4 and 5) developed by Barclay 
Mowlem Construction Ltd. of Australia were evaluated for 

strength characteristics and air leakage resistance. This program 

was funded by Barclay Mowlem. These full-scale designs were 

air leakage tested, then subjected to a series of explosions. The 

main objective of the tests was to determine if the seal and 

stopping designs were of sufficient strength and leakage 

resistance to meet or exceed the requirements of the Queensland 

Department of Mines and Energy's Approved Standard for 

Ventilation Control Devices. This objective was achieved 

during this program. 

A summary of the evaluations is listed in table 5. The two 

stopping designs withstood the first explosion test. The static 

pressure exerted on the water tube stopping was 19 Wa; the 

pressure on the air-inflated vinyl bladder Quickseal, 14 Wa. 

The vinyl water tubes, although still suspended from the mine 

roof, had drained of water because of a rupture of the bottom 

seal of each tube. The Quickseal stopping was dislodged from 

its original position, but the vinyl bladder was still inflated. 

During the second explosion test, the static pressures on the two 

450-mm-thick seals ranged from 170 to 205 Wa for the seals in 

crosscuts 3 and 2, respectively. These two seals physically 

survived the explosion, but postexplosion air leakage resistance 

data for each seal were near or slightly above the upper limit 

guidelines established for this program. 

A higher level explosion test was then conducted. The 

450-mm-thick seal in crosscut 2 withstood a peak explosion 

pressure of 370 Wa. As had been observed after the previous 

explosion test, the air leakage resistance data for this seal after 

this larger explosion test were near or slightly above the upper 

limit guidelines established for this program. The 450-mmthick, 2.8-m-high vinyl bladder seal in crosscut 3 was destroyed 

by a peak pressure of 475 Wa. 

A large part of the Barclay Mowlem program was dedicated 

to evaluating the strength and air leakage resistance of an 

innovative, full-scale overcast design when subjected to lowlevel explosion tests. This overcast design withstood four 

explosion tests, which generated overpressures at the overcast 

location ranging from 1 6 to 47 Wa. An air leakage test after the 

16-Wa explosion test revealed that the leakage through the 

overcast design fell well within the established guidelines for air 

leakage through a seal. 

A late modification to the Barclay Mowlem program was 

the evaluation of a seal design that might be capable of 

withstanding a 140-Wa explosion overpressure within -24 hr 

after construction. Therefore, a second 240-mm-thick seal, 

composed of individual vinyl tubes, was built in the 2.8-m-high 

crosscut 3 and explosion tested -24 hr after construction. This 

particular seal was destroyed by the 160-Wa explosion pressure 

gener<ated during the last test of the program. A similar seal in 

crosscut 4, composed of a series of connected 165-mm-diam 

vinyl tubes, was also destroyed by this explosion test, which 

gener<ated an overpressure of 1 15 Wa at the seal location. 

At the request of MSHA and with support from the UMWA 

and Jim Walter Resources, Inc., an innovative modification to 

the 405-mm-thick standard-type, solid-concrete-block seal 

descr1,bed in the CFR was evaluated in a third program for 

potential use in areas with friable coal where other seal designs 

had failed because of the weakness of the rib coal. This 

modiiication involved the use of pressurized grout-filled bags, 

referred to as "Packsetter bags," along the interface of seal with 

the mine roof and ribs. The purpose of the Packsetter bags was 

to eliminate the need for hitching of the seal into the mine floor 

and/or ribs. The two solid-concre te-block designs using full 

mortar joints, staggered vertical block joints, a center pilaster, 

and P'acksetter bags in place of the rib and/or floor hitching 

survived the minimum 138-Wa static pressure pulse while 

maintaining air leakage rates within the acceptable guidelines. 

A second similar seal design without the mortared block joints 

(i.e., dry-stacked) was destroyed by a 125-Wa explosion. This 

mortared Packsetter seal, when used in an entry with hable 

coal, lhas been demonstrated at the Jim Walter Resources, Inc., 

mine :in Alabama to provide a seal that can continue its intended 

function for a longer period compared with other conventional 

and al!ternative sealing methods. The mortared solid-concreteblock seals using the Packsetter bags in place of floor and rib 

hitching have been deemed suitable by MSHA for use under 

certain conditions in underground coal mines. 

NIOSH will continue to develop and/or evaluate, through 

programs similar to those discussed in this report, new and 

innovative seal designs that will provide increased protection 

for U.S. miners. These new seal designs may reduce materials 

handling, thereby reducing personnel injuries; reduce overall 

seal installation times, resulting in reduced mine personnel 

exposure when installing seals under hazardous conditions; 

and/or enhance seal performance in terms of strength characteristics, air leakage resistance, and better durability in areas of 

high convergence or unusual geological conditions. 

ACKNOWLEDGMENTS 

The authors thank John Breedlove, Vice President, Joe to the coordination, construction, and evaluation of the 

Bower, Northern Region Manager, and Rodney Howery, Sales cemerltitious pumpable seals. 

Manager, of HeiTech Corp.; Duncan Hird, Technical Sales The authors also thank Cliff Robinson, Development 

Manager, Blue Circle Special Cements, Cedar Bluff, VA; and Manager of Mine Services, Barclay Mowlem Construction Ltd., 

Phil Smith, Mining Consultant, Blue Circle Industries PLC, Moorooka, Queensland, Australia; Barry Sturgeon, Joanne 

Barnstone, U.K. These individuals significantly contributed Sturgeon, Collin Furbank, and Leslie Retschlag, formerly with 
Barclay Mowlem; and Michael Downs, BHP Coal of Australia. 

These individuals sigmficantly contributed to the coordination, 

construction, and evaluation of the high-strength cementitious 

pumpable seals, overcast designs, and stopping designs. 

In addition, the authors thank Joe Main, Administrator, 

Occupational Health and Safety, UMWA; Kenneth Randall 

Clements, President, Local 2368 UMWA District 20 during the 

test program and now Safety Committee Member, Local 2368 

of Jim Walter Resources, Inc., Blue Creek Coal No. 5 Mine, 

Brookwood, AL; Kenneth Howard, Director of Technical 

Support, and Clete Stephan, Principal Mining Engineer, of 

MSHA; Thomas McNider, Manager of Ventilation, and Scott 

Jinks, Mine Engineer, of Jim Walter Resources, Inc., Blue Creek 

Coal, Brookwood, AL; and Ed Barbour, Sales and Marketing 

Manager, and Joe Atkins, Application Technician, of Strata 

Products, Inc., Marietta, GA. These individuals contributed to 

the coordination, construction, and evaluation of the Packsetter 

seals. 

The authors acknowledge the following PRL personnel 

without whose contributions this program could not have been 

accomplished: Kenneth W. Jackson, Electronics Technician, 

and Deepak Kohli, Electrical Engineer, for sensor calibrations 

and installations, for modifications to and installation of the data 

acquisition systems, and for their participation in the testing and 

data analyses; and William A. Slivensky, Frank A. Karnack, and 

Donald D. Sellers, Physical Science Technicians, for their 

extensive participation in the installation of sensor mounting 

equipment, seal installations, construction monitoring, explosion 

and air leakage testing, and cleanup. 

REFERENCES 

CFR. Code of Federal regulations. Washington, DC: U.S. Government 

Printing Office, Office of the Federal Register. 

Greninger NB, Weiss ES, Luzik SJ, Stephan CR [1991]. Evaluation of 

solid-block and cementitious foam seals. Pittsburgh, PA: U. S. Department of 

the Interior, Bureau of Mines, RI 9382. 

Mattes RH, Bacho A, Wade LV [1983]. Lake Lynn Laboratory: 

construction, physical description, and capability. Pittsburgh, PA: U.S. 

Department of the Interior, Bureau of Mines, IC 891 1. 

Mitchell DW [1971]. Explosion-proof bulkheads: present practices. 

Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 7581. 

Queensland Department of Mines and Energy [1996]. Approved Standard 

for Ventilation Control Devices Including Seals and Surface Airlocks, 

ODM967396. Queensland Department of Mines and Energy, Safety and Health 

Division, Coal Operations Branch. 

Roxborough FF [1997]. Anatomy of a disaster: the explosion at Moura 

No. 2 coal mine, Australia. Mining Techno1 79(906):37-43. 

Sapko MJ, Weiss ES [2001]. Evaluation of new methods and facilities to 

test explosion-resistant seals. In: Proceedings of the 29th International 

Conference of Safety in Mines Research Institutes. Vol. 1. Katowice, Poland: 

Central Mining Institute, pp. 157-166. 

Sapko MJ, Weiss ES, Watson RW [1987]. Size scaling of gas explosions: 

Bruceton Experimental Mine versus the Lake Lynn Mine. Pittsburgh, PA: U.S. 

Department of the Interior, Bureau of Mines, RI 9136. 

Sawyer SG [1992]. Mortar for use in the construction of concrete-block 

stoppings and seals in underground mines. Pittsburgh, PA: U.S. Department 

of Labor, Mine Safety and Health Administration, Industrial Safety Division 

(ISD) report No. 02-174-92, June 22, 1992. 

Stephan CR [1990a]. Construction of seals in underground coal mines. 

Pittsburgh, PA: U.S. Department of Labor, Mine Safety and Health 

Administration, Industrial Safety Division (ISD) report No. 06-213-90, 

August 1, 1990. 

Stephan CR [1990b]. Omega 384 block as a seal construction material. 

Pittsburgh, PA: U.S. Department of Labor, Mine Safety and Health 

Administration, Industrial Safety Division (ISD) report No. 10-3 18-90, 

November 14,1990. 

Triebsch GF, Sapko MJ [1990]. Lake Lynn Laboratory: a state-of-the-art 

mining research laboratory. In: Proceedings of the International Symposium on 

Unique Underground Structures. Golden, CO: Colorado School of Mines, Vol. 

2, pp. 75-1 to 75-21. 

Weiss ES, Greninger NB, Perry JW, Stephan CR [1993a]. Strength and 

leakage evaluations for coal mine seals. In: Proceedings of the 25th 

International Conference on Safety in Mines Research Institutes. Pretoria, 

Republic of South Africa: Conference Papers for Day One, pp. 149-1 61. 

Weiss ES, Greninger NB, Slivensky WA, Stephan CR [1993b]. Evaluation 

of alternative seal designs for coal mines. In: Proceedings of the Sixth U.S. 

Mine Ventilation Symposium, Salt Lake City, UT: University of Utah, 

chapter 97, pp. 635-640. 

Weiss ES, Greninger NB, Stephan CR, Lipscomb JR [1993c]. Strength 

characteristics and air-leakage determinations for alternative mine seal designs. 

Pittsburgh, PA: U.S. Department of the Interior, Boreau of Mines, RI 9477. 

Weiss ES, Slivensky WA, Schultz MJ, Stephan CR;Jackson KW [1996]. 

Evaluation of polymer construction material and water trap designs for 

underground coal mine seals. Pittsburgh, PA: U.S. Department of Energy, 

RI 9634. 

Weiss ES, Slivensky WA, Schultz MJ, Stephan CR [1997]. Evaluation of 

water trap designs and alternative mine seal construction materials. In: 

Dhar BB, Bhowmick BC, eds. Proceedings of the 27th International 

Conference on Safety in Mines Research Institutes. Vol. 2. New Delhi, India: 

Oxford & IBH Publishing Co. Pvt. Ltd., pp. 973-981. 

Weiss ES, Cashdollar KL, Mutton IVS, Kohli DR, Slivensky WA [1999]. 

Evaluation of reinforced cementitious seals. Pittsburgh, PA: U.S. Department 

of Health and Human Services, Public Health Service, Centers for Disease 

Control and Prevention, National Institute for Occupational Safety and Health, 

DHHS (NIOSH) Publication No. 99-136, RI 9647. 
APPENDIX A.-SUMMARY TABLES OF AIR LEAKAGE MEASUREMENTS 

Table A-1 .-Air leakage measurements befare the first explosion test 

(No. 354) of the HeiTech program 

Air leakage rates, m3/min, 

at pressure differential ofLocation 

0.17 0.32 0.50 0.86 

kPa kPa kPa kPa 

Seal in crosscut 2 .......... 0.0 0.9 1.2 1.8 

Seal in crosscut 3 .......... 1.1 1.7 2.2 2.9 

Seal in crosscut 4 .......... 0.0 0.8 1.1 1.8 

Seal in crosscut 5 .......... 0.0 0.8 1 .O 1.7 

Table A-2.-Air leakage measurements after the first explosion test 

(No. 354) of the HeiTech program 

Air leakage rates, m3/min, 

at Dressure differential ofLocation 

0.16 0.30 0.51 1.01 

kPa kPa kPa kPa 

Seal in crosscut 2 .......... 1.2 1.8 2.7 3.5 

Seal in crosscut 3 .......... 17.0 21.9 31.6 37.5 

Seal in crosscut 4 .......... 0.8 1.3 2.1 2.9 

Seal in crosscut 5 .......... 0.9 1.3 1.9 2.7 

Table A-3.-Air leakage measurements after sealant was reapplied and 

before the second explosion test (No. 35511 of the HeiTech program 

Location 

Air leakage rates, m3/min, 

at pressure differential of0.21 0.35 0.55 1.06 

Seal in crosscut 2 .......... 1.5 2.1 2.8 3.6 

Seal in crosscut 3 .......... 0.0 c0.7 1 .O 1.8 

Seal in crosscut 4 .......... 0.9 1.3 1.7 2.7 

Seal in crosscut 5 .......... 1 .O 1.4 1.9 2.8 

Table A-4.-Air leakage measurements after the second explosion test 

(No. 355) of the HeiTech program 

Location 

Air leakage rates, m3/min, 

at pressure differential ofkPa kPa kPa kPa 

Seal in crosscut 2 .......... 1.6 2.1 2.8 3.8 

Seal in crosscut 3 .......... 0.9 1.2 1.6 2.8 

Seal in crosscut 4 .......... 1.1 1.4 2.2 3.2 

Seal in crosscut 5 .......... 0.9 1.3 1.9 3.0 
Table A-5.-Air leakage measurements before the first explosion 

test (No. 358) of the Barclay Mowlem program 

Air leakage rates, m3/min, 

at pressure differential ofLocation 

0.20 0.34 0.55 1.02 

kPa kPa kPa kPa 

Seal in crosscut 2 ........... 0.0 0.0 0.0 1.1 

Water stopping in crosscut 3 ... 13.3 19.1 27.4 - '4.8 '6.5 '9.3 '16.1 

'Second air leakage test after re-securing water tubes that were dislodged 

during first leakage test. 

Table A-6.-Air leakage measurements between the first (No. 358) and 

second (No. 359) explosion tests of the Barclay Mowlem program 

Air leakage rates, m3/min, 

at pressure differential ofLocation 

0.22 0.36 0.56 1.10 

kPa kPa kPa kPa 

Seal in crosscut 2 ........... 1.1 1.5 2.1 3.0 

Seal in crosscut 3 ........... 1.6 2.3 2.8 4.2 

Table A-7.-Air leakage measurements between the second (No. 359) and 

third (No. 360) explosion tests of the Barclay Mowlem program 

Air leakage rates, m3/min, 

Location 

at pressure differential ofkPa kPa kPa kPa 

Seal in crosscut 2 ........... 2.7 4.8 7.4 12.7 

Seal in crosscut 3 ........... 2.4 3.6 5.2 8.4 

Table A-8.-Air leakage measurements between the third (No. 360) and 

fourth (No. 361) explosion tests of the Barclay Mowlem program 

Air leakage rates, m3/min, 

at pressure differential ofLocation 

0.21 0.36 0.55 1.03 

Seal in crosscut 2 ........... 3.0 4.3 5.8 8.6 

Seal in crosscut 3 ........... ('1 ('1 (I ) ('1 

Overcast in B-drift at intersection 

with crosscut 3 ............ 1.0 1.0-1.6 1.6-1.9 2.4-2.8 

Seal in crosscut 4 ........... 0.0 0.0 0.0 0.0 

'Seal was destroyed by pressure pulse. 

Table A-9.-Air leakage measurements between the fourth (No. 361) and 

fifth (No. 362) explosion tests of the Barclay Mowlem program 

Air leakage rates, m3/min, 

at differential ofLocation 

0.21 0.36 0.55 1.03 

Seal in crosscut 2 ............ - - - - 

Overcast in B-drift at intersection 

with crosscut 3 ............. 1.7-2.2 2.5-2.8 2.8-3.7 4.5-5.3 

'1.6-2.1 '2.3-2.8 '3.2 '4.2-5.1 

Seal in crosscut 4 ............ 0.0 0.0 ~0.7 0.9 

'0.0 

A dash ( - ) indicates that no data were measured. 

'Second leakage test following gunite patching of overcast and crosscut 4 seal. 
Table A-10.-Air leakage measurements before the seventh explosion test 

(No. 364) of the Barclay Mowlem program 

Air leakage rates, m3/min, 

at pressure differential ofLocation 

0.21 0.34 0.55 1.06 

kPa E;Pa kPa kPa 

Seal in crosscut 2' ........... 0.0 0.0 1 .O 1.6 

Seal in crosscut 3 ............ 0.0 0.0 1 .O 1.7 

Overcast in B-drift at intersection 

with crosscut 3 ............. - - - - 

Seal in crosscut 4 ............ 0.0 10.0 0.0 0.9 

A dash ( - ) indicates that no data were measured. 

'Seal in crosscut 2 was re-gunited before air leakage test. 

Table A-1 1 .-Air leakage measurements after the seventh explosion test 

(No. 364) of the Barclay Mowlem program 

Air leakage rates, m3/min, 

at pressure differential ofLocation 

0.19 0.34 0.51 1.03 

kPa I(Pa kPa kPa 

Seal in crosscut 2 ............ 1 .O 1.4 2.0 2.9 

Seal in crosscut 3 ............ (' ) ('1 (' ) (') 

Overcast in 6-drift at intersection 

with crosscut 3 ............. - - - - 

Seal in crosscut 4 ............ (' 1 (') ('1 (') 

A dash ( - ) indicates that no data were measured. 

'Seal was destroyed by pressure pulse. 

Table A-12.-Air leakage measurements before the first explosion test 

(No. 365) of the Packsetter seal program wi,th the solid concrete block 

Air leakage rates, m3/min, 

at pressure differential ofLocation 

0.21 0.36 0.52 1.02 

Seal in crosscut 2 ........... 4.5 6.4 8.6 14.5 

Seal in crosscut 3 ........... 6.7 9.3 12.3 18.9 

Seal in crosscut 4 ........... 10.8 14.9 19.1 27.8 

Table 8-1 3.-Second air leakage measurements; before the first explosion test 

(No. 365) of the Packsetter seal program with the solid concrete block 

Air leakage rates, m3/min, 

Location 

at pressure differential ofSeal in crosscut 2 ........... 0.8 1.1 1.5 2.6 

Seal in crosscut 3 ........... 0.9 1.3 1.8 3.0 

Seal in crosscut 4 ........... 3.7 4.9 6.6 9.6 - '3.9 '5.0 '7.4 

A dash ( - ) indicates that no data were measured. 

'Air leakage rates obtained after reapplying sealant for a third time. 
Table A-14.-Air leakage measurements between the first (No. 365) and 

second (No. 366) explosion tests of the Packsetter seal program 

with the solid concrete block 

Location 

Air leakage rates, m3/min, 

at pressure differential ofSeal in crosscut 2 ........ 0.8 1.2 1.7 2.8 

Seal in crosscut 3 ........ 1.3 1.8 2.6 3.5 

Seal in crosscut 4 ........ 14.6 19.8 24.3 32.8 

Table A-15.-Air leakage measurements after the second explosion test 

(No. 366) of the Packsetter seal program with the solid concrete block 

Air leakage rates, m3/min, 

at pressure differential ofLocation 

0.24 0.37 0.56 1 .OO 

Seal in crosscut 2 ........... 0.9 1.3 1.8 2.8 

Seal in crosscut 3' .......... 1.7 2.4 2.9 4.5 

Seal in crosscut 4 ........... (2) (2) (*) (2) 

'prior to this air leakage test, a small (unauthorized) amount of additional sealant was 

inadvertently applied by the vendor to seal 3 at the perimeter areas where the original 

sealant was dislodged and along the block/floor interface where the sealant had 

separated during the explosion. 

2Seal was destroyed by pressure pulse. 
APPENDIX B.-SUMMARY TABLES OF STATIC PRESSURE DATA 

FOR LLEM EXPLOSIOlN TESTS 

Table B-1.-HeiTech pumpable cementitious seals evaluation in the Lake Lynn Experimental Mine: 

pressure data, test 354 (November 6,1997) 

TRANSDUCER - 

''ma Pressure-time Time of Distance, ft (m) 10-ms (1 5-pt) avg integral JPdt 

Pmaxv S - psi kPa psi-s kPa 

13 (4.0) ....................... 0.51 0 39.0 270 20.0 138 

59 (18.0) ...................... 0.495 28.5 200 6.8 47 

84 (25.6) ...................... 0.500 28.0 193 7.0 49 

134 (40.8) ...................... 0.520 27.0 185 6.4 44 

184 (56.1) ...................... 0.550 29.0 200 6.8 47 

234 (71.3) ...................... 0.578 24.0 165 5.2 36 

304 (92.7) ...................... 0.614 23.0 160 4.8 33 

403 (122.8) ..................... 0.678 22.0 150 3.9 27 

501 (152.7) ..................... 0.744 17.0 120 4.2 29 

SEAUSTOPPING 

pmax Pressure-time 

Location and distance, ft (m) Type 1 Cl-ms (1 5-pt) avg integral JPdt 

o:;i kPa ~si-s kPa 

Seal in crosscut 2: 156 (47.5) ....... Static ...... 28#.0 190 6.6 46 

Seal in crosscut 3: 246 (75.0) ....... Static ...... 24.0 165 5.1 36 

Seal in crosscut 4: 355 (108.2) ...... Static ...... 22.5 155 4.3 30 

Seal in crosscut 5: 452 (137.8) ...... Static ...... 191.5 135 4.0 28 

NOTE.-Pressure results are listed to nearest 0.5 psi and to nearest 5 kPa. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include 

the second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 1 kPa-s. 

Table B-2.-HeiTech pumpable cementitious seals evaluation in the Lake Lynn Experimental Mine: 

pressure data, test 355 (Novemlber 20, 1997) 

TRANSDUCER 

Distance, ft (m) 

'ma Pressure-time Time of 10-ms (1 5-pt) avg integral JPdt 

"ma* S ~si kPa ~si-s kPa 

13 (4.0) ....................... 0.71 7 39.0 270 22.2 

59 (1 8.0) ...................... 0.677 24.0 165 6.7 

84 (25.6) ...................... 0.685 25.0 175 7.3 

134 (40.8) ...................... 0.688 27.0 185 6.3 

184 (56.1) ...................... 0.714 28.0 195 5.7 

234 (71.3) ...................... 0.735 24.5 170 5.3 

304 (92.7) ...................... 0.780 23.5 160 4.9 

403 (1 22.8) ..................... 0.841 20.0 140 3.7 

501 (152.7) ..................... 0.91 0 16.0 110 1.8 

SEAUSTOPPING 

p,, Pressure-time 

Location and distance, ft (m) Type 10-ms (1 5-pt) avg integral J Pdt 

plsi kPa psi-s kPa 

Seal in crosscut 2: 156 (47.5) ....... Static ...... 27.5 190 6.0 41 

Seal in crosscut 3: 246 (75.0) ....... Static ...... 24.0 165 5.2 36 

Seal in crosscut 4: 355 (108.2) ...... Static ...... 22.0 1 50 4.3 30 

Seal in crosscut 5: 452 (1 37.8) ...... Static ...... 113.0 125 2.8 19 

NOTE.-Pressure results are listed to nearest 0.5 psi and to nearest 5 kPa. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include 

the second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 1 kPa-s. 
pressure data. test 359 (February 27,1998) 

TRANSDUCER 

pm, Pressure-time 

Distance, fl (m) Time of 10-ms (15-pt) avg integral JPdt 

Pmw S psi kPa psi-s kPa 

13 (4.0) ....................... 0.58 36.0 250 23.5 162 

59 (1 8.0) ...................... 0.55 27.0 185 6.1 42 

84 (25.6) ...................... 0.52 29.0 200 6.4 44 

134 (40.8) ...................... 0.54 31.5 21 5 5.7 39 

184 (56.1) ...................... 0.58 28.0 190 3.6 25 

234 (7 1.3) ...................... 0.59 26.0 180 4.2 29 

304 (92.7) ...................... 0.65 18.5 125 2.7 19 

403 (1 22.8) ..................... 0.74 15.0 100 2.0 14 

501 (152.7) ..................... 0.80 11.5 80 0.9 6 

598 (1 82.3) ..................... 0.86 8.0 55 0.7 5 

757(230.7) ..................... 0.98 5.5 40 - 

SEAUSTOPPING 

pm, Pressure-time 

Location and distance, fl (m) Type 10-ms (1 5-pt) avg integral JPdt 

osi kPa osi-s kPa 

Seal in crosscut 2: 156 (47.5) ....... Static ...... 30.0 205 4.8 33 

Total ...... 39.5 270 5.4 37 

Seal in crosscut 3: 246 (75.0) . ....... Static ...... 25.0 170 3.9 27 , 

Total ...... 32.0 220 3.8 26 

NOTE.--Pressures are listed to nearest 0.5 psi and to nearest 5 kPa. 

Pressure-time integral is calculated up to the time that the pressure trace retums to -0 psi; it does not include 

the second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 1 kPa-s. 

A dash ( - ) indicates that data were not available. 
Table B-5.-Barclay Mowlem seals evaluation in the Lake Lynn Experimental Mine: 

pressure data, test 360 (March 3,1998) 

TRANSDUCER 

Time of Distance, ft (m) Pm,, s 

Pm, 10-ms (1 5-pt) avg 

psi kPa 

90.0 620 

integral jPdt 

psi-s kPa 

55.0 379 

757 (230.7) ..................... 0.89 14.0 100 5.8 40 

SEAUSTOPPING 

'ma Pressure-time 

Location and distance, ft (m) Type 10-ms (1 5-pt) avg integral JPdt 

ps ii kPa psi-s kPa 

Seal in crosscut 2: 156 (47.5) ....... Static ...... 54 370 13.1 90 

Total ...... 55 380 14.8 102 

Seal in crosscut 3: 246 (75.0) ....... Static ...... 69 475 - - 

Total ...... 79 545 '-8 '-55 

'Integral up to time of failure. 

NOTE.-Pressures are listed to nearest 0.5 psi and to nearest 5 kP<a. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include 

the second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 1 kPa-s. 

A dash ( - ) indicates that data were not available. 

Table B-6.-Barclay Mowlem seals and overcast evaluation^ in the Lake Lynn Experimental Mine: 

pressure data, test 361 (March 26,1998) 

TRANSDUCER 

Pmm Pressure-time 

Distance, ft (m) Time of 10-.ms (1 5-pt) avg integral JPdt 

pm,, s psi kPa psi-s kPa 

13 (4.0) ....................... 1.49 4.0 27 1.5 10.5 

59 (1 8.0) ...................... 1.46 3.5 24 1.2 8.5 

84 (25.6) ...................... 1.48 3.3 23 1.1 7.5 

134 (40.8) ...................... 1.50 3.2 22 1 .O 7.0 

184 (56.1) ...................... 1.56 3.0 21 0.9 6.0 

234(71.3) ...................... 1.59 2.3 16 0.7 5.0 

246 (75.0) ...................... 1.62 2.41 16 0.8 5.0 

304 (92.7) ...................... 1.65 2.3 16 0.7 5.0 

403 (1 22.8) ..................... 1.72 1 .E) 13 0.5 3.5 

501 (152.7) ..................... 1.81 1.3 9 0.5 3.5 

598 (1 82.3) ..................... 1.87 1 .O 7 0.5 3.5 

757 (230.7) ..................... 2.16 1 .I1 8 0.5 3.5 

SEAUSTOPPING 

pm, Pressure-time 

Location and distance, ft (m) Type 10-ms (1 5-pt) avg integral JPdt 

ps~i kPa psi-s kPa 

Seal in crosscut 2: 156 (47.5) ....... Static ...... 3.1 21 1 .O 6.5 

Total ...... 3.5 24 1 .O 7.0 

Overcast, crosscut 3 and Bdrift 

intersection: 246 (75.0) ......... Static ...... 2.11 16 0.6 4.0 

Seal in crosscut 4: 355 (1 08.2) ...... Static ...... 2.1 14 0.6 4.0 

Total ...... 2. 21 16 0.6 4.0 

NOTE.-Pressures are listed to nearest 0.1 psi and to nearest 1 kPa. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include the 

second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 0.5 kPa-s. 
Table B-7.-Barclay Mowlem seals and overcast evaluation in the Lake Lynn Experimental Mine: 

pressure data, test 362 (March 31,1998) 

TRANSDUCER 

Distance, ft (m) Time of 

"maw s 

Pm, 

1 0-ms (1 5-pt) avg 

~si kPa 

Pressure-time 

integral JPdt 

pm, Pressure-time 

Location and distance, ft (m) TY pe 10-ms (1 5-pt) avg integral J Pdt 

psi kPa psi-s kPa 

Seal in crosscut 2: 156 (47.5) ....... Static ...... 5.9 4 1 1.4 9.5 

Total ...... 6.8 47 1.5 10.5 

Overcast, crosscut 3 and B-drift Static ...... 4.3 30 0.8 6.0 

intersection: 246 (75.0) ........... 

Seal in crosscut 4: 355 (108.2) ...... Static ...... 4.0 28 0.9 6.0 

Total ...... 4.7 33 0.9 6.5 

NOTE.-Pressures are listed to nearest 0.1 psi and to nearest 1 kPa. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include the 

second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 0.5 kPa-s. 

Table B-8.-Barclay Mowlem seals and overcast evaluation in the Lake Lynn Experimental Mine: 

pressure data, test 363 (April 1, 1998) 

TRANSDUCER 

''ma Pressure-time 

Distance, ft (m) Time of 10-ms (1 5pt) avg integral JPdt Pmaxt s psi kPa psi-s kPa 

13 (4.0) ....................... 0.88 16.5 114 12.0 82.0 

59 (1 8.0) ...................... 0.83 9.5 66 2.3 15.5 

84 (25.6) ...................... 0.82 9.4 65 2.2 15.0 

1 34 (40.8) ...................... 0.84 8.9 6 1 1.9 12.5 

184 (56.1) ...................... 0.88 8.9 6 1 1.5 10.0 

234 (71.3) ...................... 0.88 6.8 47 1.1 7.5 

246 (75.0) ...................... 0.92 5.8 40 1.2 8.5 

304 (92.7) ...................... 0.95 6.3 44 1.3 8.5 

403 (1 22.8) ..................... 1.02 5.9 4 1 0.8 5.5 

"ma Pressure-time 

Location and distance, ft (m) TY pe 10-ms (1 5-pt) avg integral JPdt 

psi kPa psi-s kPa 

Seal in crosscut 2: 156 (47.5) ....... Static ...... 8.9 6 1 1.7 11.5 

Total ...... 11.1 77 1.8 12.5 

Overcast, crosscut 3 and B-drift Static. ..... 6.8 47 0.9 6.0 

intersection: 246 (75.0) ........... Seal in crosscut 4: 355 (108.2) ...... Static ...... 6.1 42 1 .O 7.0 

Total ...... 7.1 49 1.1 7.5 

NOTE.-Pressures are listed to nearest 0.1 psi and to nearest 1 kPa. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include the 

second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 0.5 kPa-s. 
Table B-9.-Barclay Mowlem seals and overcast evaluation in the Lake Lynn Experimental Mine: 

pressure data, test 364 (April 3,1998) 

TRANSDUCER 

Pm, Pressure-time 

Distance, ft (m) Time of 10-rns (1 5pt) avg integral [Pdt Pmaxg S - psi kPa psi-s kPa 

13 (4.0) ....................... 0.57 38.0 265 21 .O 145 

Location and distance, ft (m) Type 10-rns (lgpt) avg integral JPdt 

psi kPa psi-s kPa 

Seal in crosscut 2: 156 (47.5) . ....... Static ...... 28.01 195 5.0 34 , 

Total ...... 35.01 240 4.8 33 

Seal in crosscut 3: 246 (75.0) ....... Static' ..... 23.01 160 - - Total ...... 29.01 200 21 .4 21 0 

Overcast, crosscut 3 and Bdrift Static.. .... 6.01 4 1 1.1 8 

intersection: 246 (75.0) ........... Seal in crosscut 4: 355 (108.2) ...... Static ...... 17.0 115 - - Total ...... 20.0 135 21 .3 29 

'Weighted average of 234 ft and 304 ft, then averaged with 246 ft. 

*Integral up to time of failure. 

NOTE.-Pressures are listed to nearest 0.5 psi and to nearest 5 kPa~. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include the 

second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 1 kPa-s. 

A dash ( - ) indicates that data were not available. 

Table B-10.-Packsetter solidconcrete-block seals evaluatio~in the Lake Lynn Experimental Mine: 

pressure data, test 365 (June 22,1998) 

TRANSDUCER 

p,, Pressure-time 

Distance, ft (m) Time of 10-nns (1 5-pt) avg integral JPdt 

Pmaxn S - psi kPa psi-s kPa 

13 (4.0) ....................... 0.548 34.0 235 23.0 159 

59 (1 8.0) ...................... 0.51 7 23.5 165 4.9 34 

84 (25.6) ...................... 0.521 22.5 1 55 5.0 34 

1 34 (40.8) ...................... 0.547 22.0 150 4.5 31 

184 (56.1) ...................... 0.571 22.0 155 4.0 28 

234 (71.3) ...................... 0.61 9 18.5 130 3.2 22 

304 (92.7) ...................... 0.650 19.5 135 2.8 19 

403 (122.8) ..................... 0.71 3 16.0 110 1.7 12 

Total ...... 27.5 190 4.6 32 

Seal in crosscut 3: 246 (75.0) ....... Static ...... 18.5 130 3.1 21 

Total ...... -30 -21 0 3.3 23 

Seal in crosscut 4: 355 (108.2) ...... Static ...... 17.5 120 2.2 15 

Total ...... -25 -170 2.3 16 

NOTE.-Pressure results are listed to nearest 0.5 psi and to nearest 5 kPa. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include 

the second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 1 kPa-s. 
Table B-11.--Packsetter solid<oncrete-block seals evaluation in the Lake Lynn Experimental Mine: 

pressure data, test 366 (June 25,1998) 

TRANSDUCER 

Pmax Pressure-time 

Distance, ft (m) Time of 10-ms (1 5pt) avg integral JPdt 

Pmax* S ~si kPa ~si-s kPa 

Pmax Pressure-time 

Location and distance, ft (m) Type 10-ms (1 5pt) avg integral JPdt 

psi kPa psi-s kPa 

Seal in crosscut 2: 156 (47.5) ....... Static ...... 26.5 185 5.3 36 

Total ...... 35.5 245 5.6 39 

Seal in crosscut 3: 246 (75.0) ....... Static ...... 22.5 1 55 4.0 27 

Total ...... -32 -220 4.1 28 

Seal in crosscut 4: 355 (108.2) ...... Static ...... 18.5 125 2.6 18 

Total ...... -27 -190 2.6 18 

NOTE.-Pressure results are listed to nearest 0.5 psi and to nearest 5 kPa. 

Pressure-time integral is calculated up to the time that the pressure trace returns to -0 psi; it does not include 

the second (reflected) pressure pulse. 

JPdt data are to nearest 0.1 psi-s and to nearest 1 kPa-s. 

A dash ( - ) indicates that data were not available. 
APPENDIX C.-SUMMARY TABLE OF: FLAME ARRIVAL DATA 

FOR LLEM EXPLOSICIN TESTS 

Table C-1 .-HeiTech and Packsetter seals evaluation in the Lake Lynn Experimental Mine: 

flame arrival time dat,a 

Flame sensor Flame arrival time, s 

distance, Test Test Test Test 

ft (m) 354 355 365 366 

0.34 

0.64 

0.66 

0.72 

0.88 

Small 

ND 

ND 

NA Data not available. 

ND No detectable signal. 

"Small" means that the signal was <1 V. 

NOTE.-Flame arrival time corresponds to 11-V signal on flame sensor. Data are relative to 

ignition time. 

Table C-2.-Barclay Mowlem seals, stoppings, and overcast evalluation in the Lake Lynn Experimental Mine: 

flame arrival time data 

Flame sensor Flame arrival time, s 

distance, Test Test Test Test Test Test Test 

ft (m) 358 359 360 36 1 362 363 364 

13 (4.0) ............. 1.120 

84 (25.6) ............ 1.287 

1 34 (40.8) ............ ND 

184 (56.1) ............ ND 

234 (7 1.3) ............ ND 

304 (92.7) ............ ND 

403 (1 22.8) ........... ND 

598 (1 82.3) ........... ND 

ND No detectable signal. 

"Small" means that the signal was <1 V. 

0.535 

0.941 

Small 

ND 

ND 

ND 

ND 

ND 

0.432 

0.793 

0.888 

Small 

ND 

ND 

ND 

ND 

0.315 

0.547 

0.584 

0.637 

0.875 

Small 

ND 

ND 

NOTE.-Flame arrival time corresponds to 21-V signal on flame sensor. Data are relative to ignition time. 
APPENDIX D.-SUMMARY TABLES OF LVDT DISPLACEMENT DATA 

FOR LLEM EXPLOSION TESTS 

Table D-1 .-Barclay Mowlem seals evaluation in the 

Lake Lynn Experimental Mine: 

LVDT data, test 358 

(February 11,1998) 

Location and 

instrument 

Maximum 

displacement, mm 

Seal in crosscut 2: 

LVDT Upper ................. 0.2 

LVDT Middle ................ 0.3 

LVDT Bottom ................ 0.1 

LVDT Right ................. 0.2 

Table D-2.-Barclay Mowlem seals evaluation in the 

Lake Lynn Experimental Mine: 

LVDT data, test 359 

(February 27,1998) 

Location and 

instrument 

Maximum 

displacement. mm 

~ealincrosscut 2: 

LVDT Upper ................. 2.3 

LVDT Middle ................ 5.6 

LVDT Bottom ................ 1.8 

LVDT Right ................. 10.7 

Seal in crosscut 3: 

LVDT Upper ................. 0.8 

LVDT Middle ................ 2.0 

LVDT Bottom ................ 1.3 

LVDT Right ................. 4.5 

Table D-3.-Barclay Mowlem seals evaluation in the 

Lake Lynn Experimental Mine: 

LVDT data, test 360 

(March 3,1998) 

Location and 

instrument 

Maximum 

displacement. mm p-- 

Seal in crosscut 2: 

LVDT Upper ................. LVDT Middle ................ LVDT Bottom ................ LVDT Right ................. 

Seal in crosscut 3:' 

LVDT Upper ................. LVDT Middle ................ LVDT Bottom ................ LVDT Right ................. 

'Destroyed. 
Table D4.--Overcast LVDT data, test 36'1 (March 26,1998) 

Instrument Maximum di:splacement, mm - - 

Deck: 

Middle ........... Toward Cdrift ..... Outby ............ 

Side wall, outby: 

Top ............. Middle ........... Middle-Right ....... Bottom ........... Wing wall: 

Middle ........... 

-- 

Up Down 

5.5 0.9 

3.0 1.4 

1.2 0.2 

Outby , lnby 

- - 

Toward Adrift . Toward Cdrift 

-0.2 -0.2 

Table D-5.-Overcast LVDT data, test 362 (March 31,1998) 

Instrument 

Deck: 

Middle ........... Toward Cdrift ..... Outby ............ 

Side wall, outby: 

Top ............. Middle ........... Middle-Right ....... Bottom ........... 

Wing wall: 

Middie ........... 

- - 

Maximum disdacement. mm 

Up Down 

14.5 15.7 

outby - lnby 

0.6 0.0 

0.5 0.0 

Toward A-drift _ Toward C-drift 

0.0 1.4 

Table D-6.--Overcast LVDT data, test 3163 (April 1, 1998) 

Instrument Maximum d~isplacement, mm - - -- - - 

Deck: Up own 

Middle ........... 15.1 15.7 

Toward C-drift ..... 16.4 14.6 

Ou tby ............ 15.2 15.6 

Side wall, outby: Outby lnby 

Top ............. 0.7 

Middle ........... 0.7 

Middle-Right ....... - 

Bottom .. - ........... 0.4 0.1 

Wing wall: Toward A-drift - Toward C-drift 

Middle ........... 0.6 2.6 

A dash ( - ) indicates that data were not available. 

Table D-7.-Seal LVDT data, test 363 (April 1,1998) 

Location and 

instrument 

Maximum 

displacement. mm 

Seal in crosscut 4: 

LVDT Middle ................ -0.1 
Table D-8.--Overcast LVDT data, test 364 (April 3,1998) 

Maximum displacement, mm Instrument 

UP Down 

Deck: 

Middle ............... 15.8 14.0 

Toward Cdrift ........ 1.4 1.4 

Table D-9.--Seal LVDT data, test 364 (April 3,1998) 

Location and 

instrument 

Maximum 

displacement, mm 

Seal in crosscut 3: 

LVDT Middle ................ 12.6 

Seal in crosscut 4: 

LVDT Middle ................ 17.0 
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