Analysis of Safety Aspects And Mining Practices For Effective

Ground Control in Surface Mining

Suresh K. Bhatt, Mining Engineer

Christopher Mark, Supervisory physical scientist

National Institute for Occupational Safety and Health

Pittsburgh Research Laboratory

Pittsburgh, PA.

ABSTRACT

Fatalities caused by highwall/spoilbank failure in the

surface mines, coal and non-metal, increased to an alarming

rate of seven during 1999. To determine the causes of slope

failure and successful mining practices, the National Institute

for Occupational Health and Safety undertook a study. The

study included:

1. A review of accident statistics;

2. A review of Federal and state mining laws pertaining to

surface mining;

3. A literature review, and;

4. Mine visits.

The study emphasized surface mines in the states of West

Virginia, Ohio, and Pennsylvania.

The review of a decade’s accident statistics using the

Mine Safety and Health Administration’s (MSHA) database

showed that approximately 40% of all ground control related

incidents reported to MSHA occurred in just four eastern

states: Kentucky, West Virginia, Pennsylvania, and Ohio. The

comprehensive literature search provided a historical

perspective of highwall stability issues. Eleven mines were

visited to obtain data on their mining practice or design.

Commodities included coal, sandstone, and limestone. Based

on the visits, five case studies were developed to represent

typical mining methods and effective ground control practices

used in eastern surface mines. Benching was found to be a

common technique to reduce the overall highwall slope angle.

Decking in the softer zones, such as shale, proved useful in

controlling damage due to blasting.

INTRODUCTION

In recent years, highwall/spoilbank failures in the surface

mines have resulted in significant loss to human lives,

property, and production. A highwall is always changing as

the process of extracting coal or ore continues. The challenge,

therefore, is to maintain a stable highwall throughout the

mine's operating life. A stable highwall requires an optimum

slope under given conditions. Effective slope design includes

determining safe and workable bench height, bench face angle

, and bench width.

To determine the relationship of mine design

parameters/practices and effective ground control in surface

mining, this study was undertaken. It included coal and

nonmetal mines, and consisted of four parts:

• A review of accident statistics for the 1988-1997 period

and Mine Safety and Health Administration’s (MSHA)

accident investigation reports for the 1996-1999 period;

• A review of pertinent Federal mining laws and the State

laws of Pennsylvania, West Virginia, and Ohio;

• A comprehensive review of relevant published literature

over the past decade; and

• Visits to eleven operating surface mines representative of

the tri-state area.

The mining laws, both Federal and state, guide the design

of surface mines; significant regulations are summarized in

Appendix A.

The data obtained from the mine visits was utilized to

prepare five case studies to show the area’s different

geological settings, operating parameters, and effective ground

control practices under existing conditions.
The knowledge gained from this research will enable better

mine planning so that the health and safety of the surface mine

worker can be improved.

ACKNOWLEDGMENTS

The authors thank the managements of mining companies for

their participation in this study, and Deno M. Pappas of the

National Institute for Occupational Safety and Health, Pittsburgh

Research Laboratory for assisting with the MSHA data base on

accident statistics.

ACCIDENT ANALYSIS

Period 1988 - 1997

Highwall accident statistics from the MSHA data base were

analyzed for the ten-year period for incident frequency, degree of

injury, nature of injury, equipment involved, coal and non-metal

breakdown, worker activity at the time of accident, and other

relevant parameters. Salient results of the analysis are presented

below.

In all, there were 428 accidents caused by the highwall

instability in active coal and non-metal mines. Four mines had

four incidents each, 13 mines had 3, 35 mines had 2, and the

remaining 303 mines had one highwall incident. Thus, a total of

355 mines reported 428 incidents during the period. Mines with

multiple incidences, three and four, are listed in Appendix B. For

each mine, number of incidents, year of occurrence, failure type

(highwall/spoilbank), degree of injury, and the commodity mined

are provided. The table 1 shows the breakdown of all accidents

by degree of injury:

Table 1. Accidents by degree of injury

Degree category (definition) Occurrence, %

0 (No injury) . . . . . . . . . . . . . . . . . . . . . . . . . 5.0

1 (Fatal) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0

2 (Permanent disability) . . . . . . . . . . . . . . . . 0.0

3 (Days away from work) . . . . . . . . . . . . . . . 57.0

4 (Days away and restricted activity) . . . . . . 5.0

5 (Days of restricted activity) . . . . . . . . . . . . 4.0

6 (No days lost) . . . . . . . . . . . . . . . . . . . . . . . 22.0

Total . . . . . . . . . . . . . . . . . . . . . . . . . 100.0

Of the 28 fatal accidents, the majority (70%) occurred in

non-metal mines. This represents approximately three fatal

accidents per year over the 10-year period. Considering all

accident incidents (428), the distribution between coal and

nonmetal mines is about 50-50. On worker exposure basis, the

incidence rate at surface coal mines is about twice that at surface

nonmetal mines. Refer to the section on surface mine worker

population.

The 428 accidents were categorized by the nature of injury

caused and are as follows (table 2):

Table 2. Accidents by nature of injury

Nature of injury Occurrence, %

Contusions, bruises . . . . . . . . . . . . . . 23.0

Multiple injuries . . . . . . . . . . . . . . . . 18.0

Cut, laceration, puncture . . . . . . . . . . 17.0

Sprain, strain . . . . . . . . . . . . . . . . . . . 8.0

Others* . . . . . . . . . . . . . . . . . . . . . . . . . 34.0

Total . . . . . . . . . . . . . . . . . . . 100.0

*Has over 30 injury classifications.

Approximately 26% of all accidents caused by highwall

failure involved heavy earth moving equipment, such as the

drill, front-end loader, dozer, shovel/dragline, and trucks.

Approximately half of the injuries were caused when the failed

material hit the victim directly. The remaining 24% involved

miscellaneous equipment items (over 40). Figure 1 shows this

breakdown.

Handling supplies or material was found to be the single

most frequent (11%) worker activity when injured, followed

by idle category (7%). Handling explosives, drilling face, and

surface equipment (not elsewhere classified) each represent

about 6% of all accidents (18% total). The remaining 64% are

distributed over 80 mine worker activities. Figure 2 shows

this breakdown.

Figure 1. Accidents by worker involvement
Surface 

Equipment

6%

Drilling Face

6%

Handling 

Explosive

6%

Handling 

Supplies

11%

Idle

7%

M isc. 

Activities

64%

Figure 2. Accidents by worker activity

Four eastern states, Kentucky, West Virginia, Pennsylvania,

and Ohio, experienced some 40% of all highwall incidents during

the study period.

Accident narratives do not provide accurate information on

the size of rock falls. It can generally be estimated that about 50%

of highwall instability incidents are caused by falling of small

rocks or fragments.

A review of months of incident occurrence does not provide

a significant correlation. In other words, winter months were not

significantly accident prone due to freeze-thaw cycles.

Current Data

MSHA's Fatalgrams and accident investigation reports were

reviewed for fatalities in 1998 and 1999. In 1998, there was one

highwall failure accident in a coal operation. In 1999, there were

seven fatalities, four in coal and three in non-metal mines. This is

over two-fold increase compared to the average of approximately

three fatalities per year during the ten-year study period. Salient

findings/data for the eight accidents are presented below.

Two accidents were caused when spoilbank collapsed, the

remaining six resulted due to falling rock from the highwall of

active mining operations. In three cases, failed highwall material

directly hit the victim; whereas, workers were operating equipment

in the remaining situations. The equipment involved in the

accidents include highwall drill, excavator (shovel), and truck.

The occupation of workers included all phases of operations, i.e.,

truck driver, drill operator, excavator/shovel operator, and a

company owner.

The size of rock falls varied between unspecified amount to

massive or extremely large. Some reports mentioned the size as

one kilogram, one tonne, and several tonnes.

Best practices, recommended by MSHA, to avoid the

accidents were given as:

• Examine and monitor highwall often.

• Follow ground control plan.

• Train miners to recognize hazardous highwall conditions.

• Scale-down or support the hazardous highwall areas.

• Keep drill and other mobile equipment operators away

from highwall face or highwall hazards by positioning

them in safe locations.

• Employ mining methods that will maintain wall, bank, and

slope stability in places where persons work or travel.

• Provide adequate berms to prevent over-travel at dump

locations.

MSHA’s accident investigation reports for the 1996-1999

period were thoroughly analyzed. Twelve fatality reports are

summarized in Appendix C. The table includes data such as

the commodity mined, types of failure, accident description,

worker activity at the time of accident, weather conditions,

citations, victim’s occupation, equipment involved, and the

height of highwall.

SURFACE MINE WORKER POPULATION

Mine Injury and Worktime, Quarterly from MSHA

provided approximate surface mine employment data for 1998:

Commodity No. of workers

Coal (includes anthracite and contractors) . 36,350

Non-metal (includes stone and contractors) 68,300

 Total . . . . . . . . . . . . . . . . . . . . . . 104,650

As can be seen from the above, over 104,000 workers are

exposed to the hazards of highwall instability in the United

States mining industry.

LITERATURE REVIEW

Literature review pertaining to slope stability is provided

below in three categories.

Mine Planning and Design

Mining parameters in a surface mine are influenced by

strata conditions and their subsequent design for actual mining

process. The structural aspects of overburden and floor

material play a significant role in the predictive behavior of

rock masses in response to the mining operations, especially of

highwall stability and the formation of spoil dumps (1), and

therefore, the choice of mining parameters. These parameters

include bench width, height, and slope angle.
Planning of open-pit mines on a business-risk basis (2)

emphasizes that confidence for slope design should be categorized

using the same fundamental approach as that adopted for resource

definitions–such as proven and possible reserves. For example, a

proven slope angle requires that the continuity of the stratigraphic

and lithological units within the affected rock mass is confirmed

in space from adequate intersections. A possible slope angle,

whereas, corresponds to typical slope angles based on experience

in similar rocks and along discontinuities. A risk balance between

mineral resources and slope angle is needed for developing

efficient mine plans.

Study of South Wales open-pit site (3) provides significant

relationships between the slope design and structural geological

factors. The geological parameters that are most relevant to rock

slope stability are:

• The persistence, attitude, and nature of discontinuities within

the rock mass.

• The shear strength characteristics both within the rock mass

and along discontinuities.

• The rock density.

• The potential for build-up of water pressure in the rock mass

and in tension cracks in rock slopes.

Bedding planes are the most common through-going

discontinuities, followed by joints, in coal measure sequences.

Transcurrent (strike-dip) faults, unless major, do not lead to slope

instability. Open-pit designs should attempt to avoid the presence

of adversely oriented structurally controlled discontinuities in the

highwall.

Gregg River Mine (4) in Alberta, Canada, had two highwall

slopes 160 and 219.5 m (525 and 720 ft) high excavated in a

dipping strata in approximately the same lithologic and structural

environment. In the earlier phase of mining, the highwall

experienced instability. In the later phase, using flatter bench face

angles, the slope did not experience any significant movements.

It was found that 50° bench face angle prevented toppling failure.

Also, horizontal drain holes in critical areas of slope were

successful in keeping water away.

A slope stability analysis performed at the Beulah lignite mine

(5) indicated that most failures were in spoil piles more than 27.4

m (90 ft) high. Circular arc failures mostly occurred when the

spoil slope were too steep for the height. The study recommended

decreasing the pit width and lowering the overall slope angle by

use of a spoil bench.

Mining Practice

Controlled blasting methods are commonly used in Australian

mines (6) to maintain pit wall stability. The methods include

cushion blasting, pre-splitting, post-splitting, and using them with

production blasts. Pre-splitting requires a row of closely spaced

blast holes drilled along the design excavation limit, charged very

lightly and detonated simultaneously before the blast holes in

front of them. It gives better results than post-splitting but is

costly. It is suitable for situations where rock strength is

moderate to very high with few joints. The desired results after

excavation is a clean face with the hole traces visible on the

final wall. Cushion blasting is the simplest and least expensive

smooth wall blasting technique. It requires the back row holes

lightly charged and are delayed sequentially and detonated after

the more heavily charged production hole in the front. Postsplit or trim blast consists of a row of parallel, closely spaced

blast holes drilled along the pit limit. The holes are charged

lightly and fired after the production blast holes have

detonated.

In the United States, poor highwall stability is contributed

partly by faulty blasting practices (7). In these cases, the

explosive energy not only fractures the rock to be excavated but

also the rock that borders the excavation.

Operating costs in open-pit mines (8) are a function of pitwall angle. As the pit-wall is steepened, less waste rock has to

be mined which results in reduced blasting, excavation, and

transportation requirements. In addition, there are dewatering

costs that include engineering design, installation of horizontal

drains or wells, pumping, and water treatment. A decision

analysis framework was used to assess the economic benefit of

pit-wall depressurization in open-pit mines. The framework

can be used to evaluate each proposed pit-wall configuration

and dewatering system design and identify the optimum

alternative.

Effective mountaintop removal operations in West

Virginia (9) require sound engineering practices. The mining

begins by clearing the trees from the permitted area so that

wood is not commingled with the waste. A contour cut is then

made on the lowest mineable seam. This mining provides

control drainage and a bench to prevent the downslope

placement of material. This is done with a large front-end

loader and end-dump trucks haul overburden to a valley fill.

After the contour cut is completed and appropriate drainage is

in place, pre-stripping for the dragline begins.

Examination and Monitoring

The need for predicting movements of large-scale slope

failure is great considering the operation hazards related to the

displacement. The focus of this study (10) was to predict

future displacement. Fourteen slope failures that progressed to

partial or total collapse were reviewed. Monitoring of

instability in coal and non-coal mines in South America was

accomplished through the use of both wire extensometers and

EDM prism surveying at the surface. In a Colombian coal

mine, although total collapse of the slope did not develop, a

greatly accelerated movement of 20.4 m (67 ft) did occur over

a four-hour period. The slope failure involved sliding along

non-daylighted, clay-shale bedding surfaces to a depth of 10.1

m (33 ft). Bedding and slope angle varied from 18 to 22° in the

121.9 m (400 ft) high footwall slope.
Figure 3. General mine location map

Middelburg Mine, South Africa, has been experiencing

highwall stability problems. The highwalls at this mine are

vertical, between 15.2 to 35.4 m (50 to 116 ft) high and are

normally aligned to suit lease boundaries. The problems include

potential toppling failure against the pre-split line and plane

failure along joints in the rock mass. The mine management (11)

has developed a rating system to identify and demarcate the

problem areas. Some of the aspects covered include:

• Bench height – higher benches being higher risk.

• Work still to be done – subsequent blasting and loading of

two seams and partings being high risk; low risk if not much

work needed.

• Presence of water.

• Presence of potential plane or wedge failures.

• Overhang or poor pre-split problems on the highwall.

Microseismic monitoring of a slope failure was attempted at

the Cardinal River open-pit mine in Alberta, Canada, in the mideighties (12). The project was not fully successful, but pointed out

problems associated with microseismic procedures applicable to

steep coal seams and geologically disturbed surroundings.

Eagle Butte Mine in Wyoming provides numerous challenges

from geotechnical stand-point as the coal seam is 33.5 m (110 ft)

thick, and overburden and interburden are weak with underclay at

the mine site. In addition, a major sand channel complicates the

stability conditions. Successful extraction of coal at this mine is

contingent upon having a sound geotechnical mine plan and an

effective slope monitoring program. A suite of field techniques

have been employed in geotechnically sensitive areas which

include surveying displacements, graphing displacements against

time, field inspections, and setting stakes along displacement

cracks (13).

Surveying methods have found widespread use as a means of

monitoring wall stability in Australian open-pit mines (14). These

methods include regular visual inspection on foot, in areas of

concern; go/no-go switches across a crack; posts placed on either

side of movement zones with measurement by a vernier calliper or

tape; surveying methods including angular intersection and

electronic distance measurements, and borehole extensometers

with a depth gauge or displacement transducer. Other methods

that may find use include:

• Terrestrial photogrammatic methods.

• Inclinometers.

• Global positioning systems.

• Radar.

• Time domain reflectrometry.

MINE VISITS

Eleven coal and non-metal mines were selected for mine

visits. The purpose of the visits was to obtain relevant

information form mine managers/engineers who are involved

in the design of surface mines and highwall stability. The

mines were selected based on parameters to include the

distribution and frequency of highwall accidents, geography,

geology, material mined, management, mining method, and

equipment employed.

In addition to gathering information from the mine

personnel, an operating surface mine was visited at each

location. The mine visits covered parts of West Virginia,

Pennsylvania, and Ohio. Materials mined include coal

(anthracite and bituminous), limestone, and sandstone. Of the

eleven mines, eight are coal, two limestone, and one sandstone.

Figure 3 shows the general location of these mines in the

eastern United States. Five case studies are provided to

represent the mining practices and safety aspects of the study

area. Typically, a case study addresses the geological setting

and operational parameters (bench width, height, and slope

angle) in a mining area for effective ground control. Figure 4

shows the geological settings and operational parameters for

the five case studies.
Figure 4. Geological settings and operational parameters

This study was limited to a small mining region with

generally good geologic/mining conditions. Complex slope

stability problems, therefore, were not encountered.

Additional mines throughout the united States may need to be

studied for answers to difficult ground control issues.

Case Study 1– Coal, Mountaintop Removal

Five coal seams are mined in benches (up to 9), two being

the main seams each with about 2.7 m (9 ft) thick coal and

separated by approximately 77.7 m (255 ft) of interburden.

The overburden over the upper seam is about 29 m (95 ft),

massive sandstone. The interburden mostly consists of

sandstone and shale with bands of clay, and number of coal

seams. The strata is almost horizontal and can be considered

strong (good rating for stability purposes). The benches are

15.2 m (50 ft) high and plus 4.6 m (15 ft) wide. Highwalls in

the area typically average 30.5 m (100 ft) and are about 15° off

vertical. Haul roads are 30.5 m (100 ft) wide with maximum

grade of 10%. Berms are maintained at 1.2 m (4 ft) or truck

axle height.

Highwalls are visually examined three or four times per

shift. Smaller charges and more decks are used in softer zones

(shale and clay) for controlled breakage within and outside

blasting area. Scaling is done using dozers, end loaders,

shovels, and dragline.

Case Study 2–Coal, Mountaintop Removal and Contour

Two coal seams are mined in three benches, the upper

seam coal being of 2.4 m (8 ft) thick and the lower one about

1.8 m (6 ft). Both seams are separated by approximately 41.1

m (135 ft). Overburden over the upper seam is massive

sandstone, 71.6 m (235 ft) thick. The interburden between the

seams is mainly sandstone with bands of clay, shale, and a

number of coal seams. The strata is almost horizontal and can

be considered strong (good rating for stability purposes). The

benches are 30.5 m (100 ft ) high and 9.1 m (30 ft) wide.

typically, highwalls are approximately 30.5 m (100 ft) high.

They, however, reach up to 106.7 m (350 ft) in places. The

highwalls are nearly vertical (off 10°). Haul roads are 38.1 m

(125 ft) wide with berms maintained at truck axle height. Presplitting is done by blasting a row of holes before production

shots.

Highwalls are visually examined three or four times per

shift. During adverse weather conditions (snow and rain), the

spoilbanks are carefully examined. Attempt is made at all

times to compact the spoil material to safe angle (<50°).

Scaling is done using dozers and backhoe.

Case Study 3–Limestone, Benching

The overburden over a limestone deposit consists of soil

and loose limestone rock, about 19.8 m (65 ft) thick. The

limestone bed lies vertically and is mined for approximately 61

m (200 ft) in depth. The general areas has minor faults and

folds, and the mineral bed can be considered strong (good

rating for stability purposes).

Mining is done in four benches, 15.2 m (50 ft) high by

15.2 m (50 ft) wide each, keeping highwalls nearly (8° off)

vertical. The maximum highwall height in this case is 15.2 m

(50 ft). Haul roads are about 18.3 m (60 ft) wide with berms

maintained at somewhat more than the truck axle height.

Highwalls are visually examined three times per shift.

Hazards are removed when they pose danger to workers or

equipment. Scaling is done with a hydraulic excavator.
Case Study 4–Coal, Area Stripping

The overburden over a 1.2-m (4-ft) coal seam is 49.1 m

(161 ft) thick, comprising of claystone, shale, sandstone,

limestone, and shaley sandstone. Majority of the geologic

column (39.6 m (130 ft)) can be divided into two groups–18.3

m (60 ft) sandstone and 21.3 m (70 ft) shale. The strata is

horizontal and can be considered strong (good rating for

stability purposes).

Highwalls in the area average 38.1 m (125 ft) high, nearly

6° off vertical. Typically, two separate lanes (plus 12.2 m (40

ft) wide each) are used for hauling material, one for empty and

the other for loaded trucks. Berms are maintained at 1.8 m (6

ft) (plus truck axle height). Highwalls are visually examined

three times per shift. Visual indicators (cracks, overhangs)

trigger more intensive scaling efforts. Also, frequency of

inspection increases to four times per shift during adverse

weather (snow and rain) conditions. By continued

experimentation, the current blasting design is arrived at to

provide smooth/clean highwalls. Scaling is done by a

dragline.

Case Study 5–Limestone, Contour (Open-pit)

The overburden over a 16.5-m (54-ft) limestone deposit

is soil, sand, and gravel, about 12.2 m (40 ft) thick, most of

which was mined earlier. The limestone bed is horizontal and

massive, and can be considered very strong (excellent rating

for stability purposes).

Mining is done in one bench, 16.5 m (54 ft) high by 12.2

m (40 ft) wide, keeping highwalls vertical. The maximum

highwall height in this case is 16.5 m (54 ft). Haul roads are

about 24.4 m (80 ft) wide with berms maintained at truck axle

height. Pre-splitting is done by blasting a row of holes prior

to production shots. Highwalls are examined visually each

shift. Any cracks and loose material that have potential for

failure are corrected immediately. Scaling is done using end

loaders and backhoes. Blasting pattern was carefully designed

to minimize damage to the nearby structures.

\

CONCLUSIONS

• Considering all accident incidences, the distribution

between coal and nonmetal mines is about 50-50. On

worker exposure basis, the incidence rate at surface coal

mines is about twice that at surface nonmetal mines.

• In half the incidents, the workers get injured when the

failed highwall material hits them directly. Workers in all

occupations are vulnerable to the highwall failure

incidents.

• No single worker activity stands out to be the most

accident prone. Just being at the pit, working or idle, puts

the worker at risk.

• Approximately 50% of highwall accidents are caused by

falling of small rocks or fragments.

• About 30-m (100-ft) highwalls can be maintained in

stable conditions if the area strata is strong, such as

massive sandstone. These highwalls are nearly vertical

(off 5 to 15°) to vertical.

• Benching improves the stability of highwalls. The bench

height normally does not exceed 15.2 m (50 ft) if the

strata comprises of multiple coal seams, shale, sandstone,

and limestone, making it somewhat weak.

• Pre-splitting in hard, massive rocks provides smooth

highwall face, improving resource recovery without

compromising highwall safety.

• Blasting pattern should be specifically designed for each

mine site. Decking or small charges, in soft rock zones

(shale and clay) minimizes damage to the highwall.

• Spoilbanks, at all times, should be kept compacted to a

safe angle (less than 50°). Thorough visual examinations

are needed in adverse weather (rain and snow)

conditions.

• Berms along the haul roads and dump areas need to be

maintained at more than the truck axle height, preferably

by 0.3 m (1 ft).

REFERENCES

1. Mishra M P. Benches-Haul Roads–berms and Spoil

Heaps in Open-cast Mining. Journal of Mines, Metals,

and Fuels, January 1998, pp. 14-18.

2. Steffen OKH. Planning of Open Pit Mines on a Risk

Basis. Journal of the South African Institute of Mining

and Metallurgy, Mar/Apr 1997, pp. 47-56.

3. Gayer R, Hathaway T. Davis J. Structural Geologic

Factors in Open Pit Coal Mine Design. European Coal

Geology, Geological Society Special Bulletin No. 82,

1995, pp. 233-249.

4. Stewart AF, Gilmore BM, Pearson MJ, Savoie LM.

Improving Highwall Stability at the Gregg River Mine.

Mining Engineering, Nov. 1998, pp. 49-52.

5. Vender CS. Knife River's Beulah Mine–A Three-Seam

Challenge. Mining Engineering, Apr. 1991, pp. 396-398.

6. Pilcher BC. Controlling Blasting Operations and

Highwall Stability in Surface Mining in Australia.

Mining Technology, Vol. 79, No. 914, 1997, 10 pp.

7. Stachura VJ, Cumerlate CL. Changing Powder

Distribution in the Highwall Holes Reduces Overbreak

and Rockfall Hazards. In the Proceeding of the 15th

Conference on Explosives and Blasting Techniques,

Nov., New Orleans, LA, 1989, pp. 11-24.

8. Sperling T, Freeze RA. A Risk-Cost-Benefit Framework

for the Design of Dewatering Systems in Open Pit Mines.

Canadian Geotechnical Conference, 1987, pp. 65-66.

9. White MA, Barata FA. State-of-the-Art in Mountaintop

Removal and Contour Mining. Mining Engineering,

Dec. 1995, pp. 1111-1114.
10. Ryan TM, Call RD. Applications of Rock Mass

Monitoring for Stability Assessment of Pit Slope Failure.

Rock Mechanics Proceedings of the 33rd Symposium,

Santa Fe, NM, June 1992, pp. 221-229.

11. Latilla J. Personal communications. Middelberg Mine,

South Africa, June 1999.

12. Stuart N, Vladut T. Microseismic Data Processing

Associated with Monitoring of Mine Slope Instabilities.

Canadian Geotechnical Conference, 1986, pp. 51-58.

13. Nicholson M, Preber T, Scott TR. Field Monitoring and

Mining Methods Used at the Eagle Butte Coal Mine.

Western Regional Conference on Precious Metals, Coal

and Environment, 1994, pp. 16-29.

14. Lang AM, Swindells CF, Higham GJ. Survey Based

Open Pit Wall Monitoring. Australian Conference on

Geotechnical Instrumentation and Monitoring in Open Pit

and Underground Mining, Kalgoorlie, Australia, 1993,

pp. 303-309.

APPENDIX A.–FEDERAL AND STATE LAWS

Significant regulations pertaining to surface mine design

are paraphrased in this appendix. For details and complete

language, refer to particular stipulations in the relevant book.

FEDERAL REGULATIONS

Code of Federal Regulations, 30, Minerals Resources,

stipulates regulations for coal and non-metal resources using

surface mining methods. It provides guidance for mine design

including ground control coal, crushed stone, and non-metal

mines.

Coal

Part 77, subpart K provides regulations for coal and

significant regulations are discussed 

below.

• Each operator shall establish and follow a ground control

plan for the safe control of all highwalls, pits, and

spoilbanks, which shall be consistent with prudent

engineering design and insure safe working conditions.

The mining methods employed by the operator shall be

selected to insure highwall and spoilbank stability. A

copy of such plan shall be filed with the appropriate coal

mine health and safety district office.

• Loose hazardous material shall be stripped for a safe

distance from the pit top or highwall and the loose

unconsolidated material shall be sloped to the angle of

repose or barriers, baffle boards, screens, or other devices

be provided that afford equivalent protection.

• To insure safe operation, the width and height of benches

shall be governed by type of equipment to be used and

operation to be performed.

• Highwall banks, benches, and terrain sloping into the

working areas shall be examined after each rain, freeze,

or thaw before men work in such areas, and such

examination shall be made and recorded. Overhanging

highwalls and banks shall be taken down and other

unsafe ground conditions shall be corrected promptly, or

the area shall be posted.

• Hazardous areas shall be scaled before any other work is

performed in the hazardous area. When scaling of

highwalls is necessary to correct conditions that are

hazardous to persons in the area, a safe means shall be

provided for performing such work. Whenever it

becomes necessary for safety to remove hazardous

materials from highwalls by hand, the hazardous material

shall be approached from a safe direction and the

material removed from a safe location.

• Men, other than those necessary to correct unsafe

conditions, shall not work near or under dangerous

highwalls, and those involved in repair work shall take

special safety precautions.

Non-Metal and Crushed Stone

Part 55.3 addresses ground control of non-metal mines

and Part 56.3 covers crushed stone operations. Regulations

for both are identical and include the above stipulations for

coal. There are, however, a few additions as discussed below:

• Material, other than hanging material, to be broken by

secondary drilling and blasting, shall be blocked to

prevent hazardous movement before persons commence

breaking and will work from a safe location, if the

material movement occurs.

• A scaling bar of sufficient length shall be provided where

manual scaling is required.

• When rock bolts are used for ground support, anchorage

test procedures shall be established and tests will be

conducted to determine the anchorage capacity of rock

bolt installation.

STATE MINING LAWS

State mining laws for the three states that pertain to

surface mine design including ground control are presented

below.

Pennsylvania

For anthracite mines, while excavating, the spoilbanks

and earth cuts shall be sloped no more than 45°. An

examination shall be made at frequent intervals to determine

if danger exists from slides or overhang and when such

conditions present, they shall be immediately corrected.

Chapter 77, Title 25 of the Pennsylvania Code deals with

noncoal mining and pertinent regulations are discussed below.
• The maximum height of the working face of a bench in

consolidated material may not exceed 15.2 m (50 ft), and

that in unconsolidated material may not exceed 7.6 m

(25 ft). A waiver may be granted for greater or lower

working heights if geologic and safety considerations

(stability analysis) so require. The minimum width for a

horizontal bench between successive working faces shall

be 7.6 m (25 ft).

• An operator shall provide a stability analysis when

requesting a waiver for developing greater than 15.2 m

(50 ft) face. The analysis shall include a stereo net

analysis or equivalent for the working face strata. Manmade features within a distance equivalent to three times

the maximum proposed depth of the pit measured from

the maximum lateral extent of the final working face shall

be identified.

• There are no specific regulations for surface mining of

coal that pertain to slope stability.

West Virginia

Regulations for open-pit coal and limestone mines are

identical and are provided in Title 56, Series 6 and 7,

respectively, which originate from the Office of Miners'

Health, Safety and Training. Significant stipulations are

presented below.

• Highwall overburden shall be sloped to minimize slides

and overhanging ledges and all loose material scaled.

• If the highwall shows evidence of movement, or appears

to be weakened in anyway, the areas shall be made safe

or abandoned and dangered off.

• Blasted material shall be loaded in such a manner as to

minimize the danger of rock slides endangering

workmen.

• Regulations for quarry operations are included in Title

56, Series 3. Significant stipulations are as follows,

which are in addition to the above.

• When a bench is required to insure safe operations, its

width and height shall be governed by the type of

equipment to be used, the operations to be performed,

type of material, and height of the walls.

• Spoilbanks shall be kept free of bodies of water and spoil

material shall be sloped to the angle of repose or other

measures taken to prevent the material from sliding into

the pit.

Ohio

Ohio state mine safety laws do not have specific

requirements pertaining to the highwall/slope stability in coal

and non-metal surface mines.

APPENDIX B. HIGHWALL FAILURE- MINES WITH MULTIPLE

INCIDENCES (MORE THAN TWO) 1988-1997

Line ref. Mine, state Year Commodity

mined Highwall/spoilbank Degree of

injury

No. of

incidences

Fatalities

1 Coal mine, AL 90,91,92,92 Coal Highwall 3 4

2 Coal mine, KY 90,91,91,92 Coal 1 Spoilbank, 3 Highwall 6,3,3,3 4

3 Coal mine, PA 91,91,93,93 Coal Highwall 1,3,3,0 4 One

4 Coal mine, WV 92,92,94,95 Coal Highwall 6,3,3,3 4

5 Coal mine, IL 89,91,92 Coal Highwall 3,3,3 3

6 Non-metal mine, KY 91,91,97 Stone Highwall 4,3,5 3

7 Non-metal mine, KY 90,90,95 Stone Highwall 1,6,6 3 One

8 Coal mine, MT 93,94,94 Coal Highwall 0,0,0 3

9 Non-metal mine, PA 90,95,95 Slate Highwall 6,3,3 3

10 Non-metal mine, VT 92,94,96 Granite Highwall 3,1,4 3 One

11 Coal mine, PA 88,89,90 Coal Highwall 6,0,3 3

12 Non-metal mine, VT 94,94,95 Slate Highwall 3,3,3 3

13 Non-metal mine, WA 95,95,95 Stone Highwall 1,3,1 3 Two 

14 Coal mine, WV 90,90,92 Coal Highwall 3 3

15 Coal mine, WV 93,94,94 Coal Highwall 3,3,6 3

16 Coal mine, WV 89,90,96 Coal Highwall 1,6,3 3 One

17 Non-metal mine, MO 88,88,91 Stone Highwall 6,6,3 3

Source: Mine Safety and Health Administration
APPENDIX C.-- HIGHWALL FATALITIES 1996-1999.

Line

ref. Mine, state Date Commodity Spoilbank/ Highwall Msha category Final highwall, ft Overburden geology Special features cited Accident description Rock volume Weather Citations issued Occupation Equipment involved

1 Non-metal

Mine, AL

Oct-99 Limestone Highwall Fall of Highwall 110 Limestone Splicing cable when rock fell,

hit his head.

Small rocks Failure to scale loose

ground, to exam, test loose

ground above work area.

Electrician

2 Coal Mine,

PA

May99 Anthracite Spoilbank Fall of Highwall 130 Spoil-rock and dirt Preparing to load truck when spoil pile collapsed on

shovel.

Few tons Failed to report, correct

hazardous conditions, no

benching approved in plan. 

Shovel

Operator

Shovel

3 Non-metal

Mine, AL

Mar99 Limestone Highwall Machinery 95 Clay seam in highwall Removing mud seam when rock fell, hit equipment 2,700 lb Clear, warm Failed to exam highwall, failed to scale loose

ground, failed to log exam

record.

Excavator

Operator

Excavator

4 Coal Mine,

IN

Feb99 coal Highwall Fall of Highwall 74 Shale, sandstone, 3

coal seams

Faults

/fractures

Walking to highwall when

rock fell, hit him.

7 cu yd Cloudy, 

snow 

Failed to exam highwall,

unsafe conditions existed,

inadequate ground control

plan.

Driller

5 Non-metal

Mine, AL

Feb99 Limestone Highwall Fall of Highwall 232 Limestone, shale & mud Drilling hole, rock fell, hit in head, hard hat broken. 2 lb, 13 oz Cloudy, rains Failed to scale loose ground, method did not

provide wall stability, no

benching used.

Driller

6 Coal Mine,

WV

Jan-99 Coal Spoilbank Powered

Haulage

when dumping spoil, pile

failed under wheels, truck fell

below.

Freeze, thaw,

rain

Middle dump collapsed

under truck weight.

Truck Driver Truck

7 Coal Mine,

KY

Jan-99 coal Highwall Fall of Highwall 60 Sandstone &

shale

Faults/open

joints

Drilling near highwall base,

when rocks fell.

Large

sections

Freeze, thaw Unsafe ground conditions

,not corrected or posted, no

new employee training

given.

Driller Drill

8 Coal Mine,

KY

Oct-98 Coal Highwall Fall of Rock 73 Sandstone &

shale

While drilling hole, large

rock fell.

210 cu ft Sunny, 84° Loose rock not scaled,

inadequate on-shift exam,

ground control plan not

followed.

Driller Drill

9 Non-metal

Mine, MO

Feb97 Limestone Highwall Fall of Highwall While operating, rock fell on excavator 14,400 cu ft Hazardous ground conditions not corrected,

incomplete highwall exam.

Excavator

Operator

Excavator

10 Coal Mine,

KY

Dec96 coal Highwall Fall of Material 65 Silt, clay, sand &

gravel

Highwall

intersected

old river

channel

Loading truck when mud &

water flooded backhoe.

Large

volume

Rain, 32° Backhoe

Operator

Backhoe

11 Non-metal

Mine, NC

May96 Sandstone Highwall Fall of Highwall 30 Sandstone End loader removing waste, worker hit by loose rocks. 3 cu ft Highwall not scaled properly, not wearing hard

hat.

Vice President

12 Non-metal

Mine, PA

Dec96 Limestone Highwall Fall of Ground 44 Limestone Standing on overhanging ledge that gave in, fell

covered with rock.

Ground conditions not

corrected, post blast exam

of loose ground not made.

Blaster

Source: Mine Safety and Health Administration