Study of Reverse Torque Ratio in

the Helical Probe Test

iT'L INST. OF STAND & TECH

NBSIR 8

Koo Young Chung

Korea Institute of Construction Technology,

Civil Engineering Division 2

377 Mansu-Dong, Nam-Gu, Inchon 160-01

Republic of Korea

and

Felix Y. Yokel

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Gaithersburg, MD 20899

September 1986

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

QC

100

.U56

NO. 86-3423

1986 c.SL

NBSIR 86-3423

STUDY OF REVERSE TORQUE RATIO IN

THE HELICAL PROBE TEST

Koo Young Chung

Korea Institute of Construction Technology,

Civil Engineering Division 2

377 Mansu-Dong, Nam-Gu, Inchon 160-01

Republic of Korea

and

Felix Y. Yokel

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Gaithersburg, MD 20899

September 1986

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

ABSTRACT

A helical test probe, developed by the National Bureau of

Standards for shallow soil exploration does not extract soil

samples from the ground. A study was therefore conducted to

determine whether the ratio of the torque required to extract the

Helical Test Probe to the torque required to advance the probe

(the reverse torque ratio) can be used to determine the average

grain size (Dcjq) of the soil. On the basis of 274 test points in

sandy, silty, and clayey soils, it was concluded that the reverse

torque ratio decreases with increasing average grain size. The

relation between grain size and reverse torque ratio is apparently not sensitive to the magnitude of the torque required to

advance the probe.

Key Words : Const ruction supervision; field test equipment; helical

augers; in situ measurements; penetration tests; soil

investigation; test procedures.
.
TABLE OF CONTENTS

1. INTRODUCTION 1

2. TEST RESULTS 3

3. ANALYSIS OF TEST RESULTS 17

4. CONCLUSIONS 21

5. REFERENCES 21

6. ACKNOWLEDGEMENT 21

v
LIST OF TABLES

Table 1. Average Values of Reverse Torque Test Results 4

Table 2. Reverse Torque Ratios for the Groveton, VA Site .... 5

Table 3. Reverse Torque Ratios for 20 in-lb Torque Increments

at the Groveton, VA Site 6

Table 4. Reverse Torque for the McLean, VA Site 7

Table 5. Reverse Torque Ratios for 20 in-lb Torque Increments

at the McLean, VA Site 8

Table 6. Reverse Torque Ratios for the NBS Site 9

Table 7. Reverse Torque Ratios for 20 in-lb Torque Increments

at the NBS Site 10

Table 8. Reverse Torque Ratios for the Kingstowne, VA Site .. 11

Table 9. Reverse Torque Ratios for 20 in-lb Torque Increments

at the Kingstowne, VA Site 12

vi
LIST OF FIGURES

Figure 1. Grain Size Distribution for the Groveton, VA Site . 14

Figure 2. Grain Size Distribution for the NBS Site 15

Figure 3. Grain Size Distribution for the Kingstowne, VA Site 16

Figure 4. Correlation Between D^q and Reverse Torque Ratio .. 18

Figure 5. Variation of R with t 12 19

vn

1. INTRODUCTION

The National Bureau of Standards developed a helical test probe

for shallow soil exploration. In a previous study [1] the results

of helical probe tests (HPT) were correlated with other commonly

used in-situ tests, including the Standard Penetration test

( SPT ) , the Cone Penetration test (CPT) , and the flat plate

dilatometer test (DMT) , and it was shown that the results

obtained in these latter tests can be predicted on the basis of

the HPT torque. It was also shown that the HPT test can be used

to predict the dry density of compacted soils.

For shallow soil exploration, the HPT test is much more practical

and economical than other in-situ tests. However, when compared

with the SPT test, it has the disadvantage of not retrieving a soil sample. Thus, if it is important to determine the soil type,

soil samples have to be retrieved separately. The CPT test also

does not retrieve samples, but the soil type can be infered from

the correlation between the tip resistance and the side friction.

A similar parameter could probably also be derived from the HPT

test. When the helix is advanced, the torque needed is a measure

of the force required to penetrate the soil, expand a cavity for

the helix within the soil, and overcome the frictional resistance

of the sides of the helix. When the helix is retracted, the

torque required to retract the helix is solely a measure of the

frictional resistance of the side of the helix.

The ratio between the torque required to retract the helix and

the torque required to advance the helix is herein defined as the

"Reverse Torque Ratio" (R)

This report is part of a study which

has the objective of determining whether the reverse torque ratio

can be correlated with the soil type and used to characterize the

soil without retrieving soil samples.

1

2. TEST RESULTS

A total of 274 reverse torque measurements were performed in 32

separate test holes. Of these, 179 measurements in 20 borings

were in residual silts, 53 measurements in 6 borings were in

sands, and 42 measurements in 6 borings were in clays.

Average values for the test results are summarized in Table 1. In

the table, the soil type in Column 2 is defined in accordance

with ASTM D2487 [2]; "n" in column 3 is the number of tests; t -]_

in column 4 is the downward torque measured with the Y12 (3/4

inch diameter) test probe (refer to [1]); TR^ in column 5 is the

reverse torque taken in the same location as the torque in column

4 (the probe was turned 180° in the counterclockwise direction)

column 6 shows the reverse torque ratio , R, in percent [ (TR/t) x 100]; column 7 shows data on SPT blowcount, N, (if available);

column 8 shows CPT tip resistance, qc

, (if available); column 9

shows relative compaction data, RC, (ASTM D 1556 [3] ) , (if available) ; column 10 shows dry density, 7(^; and column 11 shows grain

size D^g, below which 50% of the sample by dry weight is smaller.

Tables 2 to 9 present the detailed test results. Tables 2 and 3

are for the Groveton, VA site (CH) , tables 4 and 5 are for the

McLean, VA site (ML) , tables 6 and 7 are for the NBS site (ML)

,

and tables 8 and 9 are for the Kingstowne VA site (SP)

For each site the test results are given in two tables. The first

table shows the test results for each boring. The downward arrows

signify downward torque, the upward arrows upward torque, and R

is the reverse torque ratio. The average reverse torque ratio, R,

and sample standard deviation, sR, for each depth range for all

the borings are listed in the last column to the right. The

average of the torques, reverse torques, and reverse torque

ratios for each boring , as well as the sample standard deviation

3
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l l «-h

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5
Table 3. Reverse Torque Ratios for 20 in-lb Torque Increments

at the Groveton, VA Site

Torque

(lb-in)

1

1 1 - 20

1

1 21 - 40

1

1 41 - 60

No.

1 ’

1

1 / / R 1

1 / / R 1

1 / / R

1

1

1 15 14 93.3

1

1 25 13 52.0

1

! 42 25 59.5

2

1

1 19 12 63.2

1

1 30 14 46.7

1

1 44 30 68.2

3

1

1 12 6 50.0

1

1 28 18 64.3

1

1 53 29 54.7

4

1

1 16 7 43.8

1

1 31 23 74.2

1

1 41 24 58.5

5

1

1 18 7 38.9

1

1 25 12 48.0

1

1 41 24 58.5

6

1

1

1 19 11 57.9

1

1 36 16 44.4

1

1 43 26 60.5

7 1

1 16 8 50.0

1

1 36 18 50.0

1

I

8

1

1

1

1 35 21 60.0

1

1

9

1

1

1

1 36 22 61.1

1

1

10 1

1

1

1 27 10 37.0

1

1

11 1

1

1 33 15 45.5

1

1

12

1

1

1

1

1 29 19 65.5

1

1

13

1

1

1

1 31 18 58.1

1

1

14 1

1

1 24 15 62.5

1

1

15

1

1

1

1 28 17 60.7

1

1

16

1

1

I

1

1 28 18 64.3

1

1

17 1

1

1

1 27 18 66.7

1

1

18 1

1

1 32 20 62.5

1

1

19

1

1

1

1 38 24 63.2

1

1 20

1

1

I

1

1 22 12 54.5

1

1 21

1

1

|

1

1 30 14 46.7

1

1 22

1

1

1

1 35 16 45.7

1

1

23

1

1

|

1

1 38 24 63.2

1

1

24

1

1

1

1 27 11 40.7

1

1

25

1

1

1

1 30 14 46.7

1

1

26

1

1

1

1 35 15 42.9

1

1

27 1

1

1 37 23 62.2

1

1

28

1

1

1

1 36 26 72.2

1

1

29

1

1

1

1 38 26 68.4

1

1 Average 1 16 4 9 .3 56.7 1 31. 3 17. 7 56.2 1 44 0 26. 3 60.0

SR 1 (18.1) 1 (10.1) 1 (4.5)

6
Table

4.

Reverse

Torque

Ratios

for

the

McLean,

Va

Site

f-i-i I -- 14-

i i in co rH <o CN VO CO in rH vo i

i cc in VO CN (Tv CN ao r* o in i «r *y m in m *y •«y in m '

i

i 00 *y

1 1 i V o ON m o <71 <71 o o CO av

i co rH CN CN *"* rH CN CN CN rH

av

1 H CN rH CO OV CN m CN rH o CO CN CO CO *y *y ^y *y CO

OV CO rH CN C7V vo co © r- ___ I CN |

1 cc VO CN rH rH *y CO CO av CN • | CO m m r- m *»y in m m o | rH |

1 r- CN w 1

i l I N av in CN co co GO rH co av

rH CN CN CN rH rH CN CN rH

1 co CO

J X rH CO CO CO CN CO VO av VO

CN CO *y CO CO CO CO CO CO

O o o •*y *y CO VO av o *y - ! • • • • • • • • • CN I

1 cc "T CN rH in r- CO o av in • | CN CN *y co *y VO m *y *y VO i rH |

1 VO VO w 1

1 1 1 vo CN <71 o co O’ CN GO in VO

rH CN CO CN «y •*y CN CN CN

1 co

CO

1 ^ m o <T> CN in CN CN in rH vo

CN m VO vo <7V VO in in in

CN m rH m m CO O o CO rH

p* t

t cc r» rH <7V vo CO r-> VO in • i TT m m <y m «y in 'y *y CN 1 rH |

l in co w 1

! i

1 "V. m CN CN CN o CN rH co •«y CN CO CN CN CO CO CN CN CN

1 co CO

1 N* (Tv CO VO r- CO o vo o av O

CN m in co •<T VO vo in in in —. m m o r* vo in co •*y in r- 1 CN |

1 cc co vO CO o VO CN 03 •<y CN vo • | CO <y *r in **y in m *y VO |

i

1 | 1 © ON CO o- rH o VO r-* CN av

rH CN CN CN CN CN rH

1 CO CN

1 ^ m CN in O m CO CO CN CO

CN in vo vO *y CO CO CO •*y *T m CO o co r* in av VO O 1

1 cc m VO o VO CO o- rH vo in • 1 CO »y VO CO *y m in *y in av i

1 co p*

l 1 1 co av vo <7v av o co 00 rrH CN CN CO CN CO CO CO CN

1 co av

1 '•» m CN OV CO CO rH 00 r* CN »T *y r- GO m in r* vo in

CO CO © CO p- o r* av

• av i

1 cc VO <7v co o <7V o © CO vo rH • | CO CO CN in **r •«T in CO N" *y r* i

1 CN vo

1 1 1 ^ CO in CN in CO r- CD VO av

rH CN CO CO CO CN N* CN

1 co 1 CN

1 ^ av CO av rH r—\ ^r CO 00 O

rH CO GO GO r~ GO r» GO av P*

O in o in o in o in o

U

1 4-1 rH rH CN CN co CO HT **r in a>

1 cr» i i

1 sc 1 1 1 1 I 1 1 1 i <TJ

1 4J k-j

1 a m o m o in o in o in 0J I I

1 a; > oc | 1 Q o »-* CN CN CO CO -*r < c/) i

7
Table 5. Reverse Torque Ratios for 20 in-lb Torque Xncreaent

at the McLean, VA Site

Torque 1 (lb-in)

1-20 21 - 40 41 - 60 61 -

1 80 | 81 -1 100 | bo re

1 than 100 | No.

| / / R 1 f R 1 / / R / R 1

1 / / R ! /

1 t R |

1

i

i

1 19 7 36.8 1 33 13 39.3 1 41 19 46.3 71 35

1 49.3 1 89 25

1 28.1 |103 46

1 39.3 1

2 1 24 8 33.3 1 45 27 60.0 74 37 50.0 | 84 42 50.0 |119 56 47.1 |

3 1 23 10 43.5 1 S3 29 54.7 72 26 36.1 1 81 33 40.7 1130 56 43.1 1

4 1 38 20 52.6 1 58 30 51.7 71 33 46.5 1 83 28 33.7 | 1

5 1 33 16 48.5 1 52 19 36.5 68 38 55.9 | 98 46 46.9 1 1

6 1 31 17 54.8 1 45 21 46.7 65 28 43.1 | 89 39 43.8 | 1

7 1 29 5 17.2 1 42 22 52.4 66 31 47.0 | 92 44 47.8 | 1

8 1 37 22 59.5 1 53 22 41.5 69 29 42.0 1 82 27 33.9 | 1

9 1 25 6 24.0 1 56 32 57.1 65 23 35.4 | 61 36 44.4 | 1

10 1 21 9 41.9 1 43 20 46.5 62 42 63.6 | 81 37 45.7 | 1

11 1 38 14 36.8 1 60 24 40.0 61 31 50.8 | 82 38 46.3 | 1

12 1 32 23 71.9 1 60 32 53.3 68 23 33.8 | 86 29 33.7 1 1 13 1 33 18 54.6 1 SO 28 56.0 80 31 38.8 1 9< 40 41.7 1 1

14 1 37 18 48.7 1 59 27 45.8 77 35 45.5 1100 40 40.0 | 1

15 1 36 21 58.3 1 50 12 24.0 65 26 40.0 | 86 32 37.2 1 1 16 1 39 23 59.0 1 42 30 71.4 65 25 38.5 1 86 48 55.8 1 1

17 1 22 10 45.5 1 55 28 50.9 61 34 55.7 1 1 1

18 1 39 20 51.3 1 51 25 49.0 80 38 47.5 1 1 1

19 1 32 19 59.4 1 48 25 52.1 1 1 1 20 1 30 8 26.7 1 43 22 51.2 1 1 1

21 1 40 18 45.0 1 41 19 46.3 1 1 1

22 1 40 19 47.5 1 48 25 52.1 1 1 1

23 1 40 21 52.5 1 45 19 42.7 1 1 1

24

1

1 23 8 34.8 1 42 20 47.6

j

1

i

I

i

i 25 1 31 14 45.2 1 41 20 48.9

1

1

1

1

1

1 26 1 36 16 14.4 1 40 23 57.5

1

1

1

1

i

i 27 1 38 20 42.6 1 42 15 35.7

1

1

1

1

1

1 28 1 31 18 58.1 1 55 27 49.1

1

1

1

1

1

1 29 1 34 16 47.1 1 46 21 45.7

1

1

1

1

1

1 30 1 32 16 50.0 1 44 19 43.2

1

1

1

1

1

1 31 1 29 22 75.9 1 43 23 53.5

1

1

1

1

1

1 32 1 38 22 57.9 1 42 22 52.4

|

1 i

1

1 33 1 21 9 42.9 1 42 25 59.5

1

|

1

1

1

1 34 1 35 22 62.9 1 46 26 56.5

1

1

1

1

1

1 35 1 40 22 55.0 1 53 20 33.7

1

1

1

1

1

1 36 1 37 23 62.2 1 43 17 39.5

1

1

1

1

1

1 37 1 40 19 47.5 1 42 20 47.6

1

1

1

1

I

1 38 1 32 7 21.9 1 44 27 61.4

1

1

1

1

1

1 39 1 21 11 52.4 1 41 24 58.5

1

1

11

|

1 40 1 40 21 52.5 1 42 16 38.1

1

1

1

1

1

1 41 1 33 16 48.5 1 47 21 44.7

1

1

I

1

|

1 42 1 35 16 45.7 1 48 22 45.8 1

1

1

1

1

1

| 43 1 37 18 48.7 1

1 1

1

1

1

1

44 1 1 29 6 20.7

1

1

1

I

j

I 45 1 1 22 6 27.3 1

1

1

1

1

j

I 46 1

|

1 40 — l 23 57.5

1

1

1

1 i Average 1 19.0 7.0 36.8

{ 32.7 15.8 47.3 47.2 23.0 48.7 68.9 31.4 45.5 i 87.3 14.5 41.9 1117.) 52.7 41.3 i SR 1 (12.8)

j

(8.6) i (8.0) | (7.2) 1 0.911

8
Table

6.

Reverse

Torque

Ratios

for

the

NBS

site 4 I CM VO CM pH VO in av CO or 1 QS 1 • i ca i m av CM Ov CO in xr •*T pH

pH pH pH * o o pH in r* 00 r* X* Ov CO CM i o> 1 ICX 1 o r«* CO m fO in CM 00 CO P- 1 O' co CM CO CO o CO o X» O CO 4 *3 1 M ro CM r** CO ao CO O o O’ 1 11 • ^ i • 1 > 00 ro VO o Ov pH ao VO xr in i < pH pH CM CM CO CO CO CO CM r- CM CM m CM CO CO VO CO o i ^ * 00 av CM pH O ao o •«T ao vo

(N xT in VO P* CO av p* r- VO

ro CM pH CO o pH o X* pH CO -

vO i ss i av Ov CM o pH O o r- CM pH • ro CM CO O CO m vO HT o

pH P^ — 1 VO i i pH CO o in 00 CM VO in

pH pH pH CM CM CM or CO CO CMr* I s. I 00 00 VO av pH CO O ao GO pH

CM

Om VO av 00m VO

pH Ov vo CO ao vo CO pH

VO 1 06 1 00 O o o P- CO Ov pH Ov x*1 • CM CM CO CO CO CM CO CO ao VO 1 m 1 V. 1 vo OS in OV 00 m in CM CM

pH pH CM CM CO CO CO CMpH• 1 % 1 VO ro ON CM in ao 00 av CM VO r* 00 00 VO VO

CM CM CMm r* vo X* ao CM

m 1 06 1 00 m pH VO av vo av CM

CM pH pH CO CM CO COm XT CO CM

pH VO w l ^ i "k i 00 CM o o pH o vo O rH

pH pH pH CM CO CO CO CO CM i \ i CO VO VO O in 00 CM 00 p* m

ro VO VO

m r* 00 VO VO VO

ro pH CO av pH o 00 CO

CM

r-* CO pH CM av CM 00 1 06 1 CM CM to <o H1 CM CO 00

XT l co VO av m m VO CM 00 XT i •k i pH CM CM CO •xr CO CM

av

CM av 00 VO HT in r- CM 1 V* 1 CM CO M* in VO ao av CO VO pH © © CM in 00 ao X* av

_ • xr CM VO VO pH r- r* av av CM in • 1 06 1 m CM r> CM CO CO CO CO ao CO 1 CM

00 CO rO CM r* CO ao ao t 1 pH pH CM CO CO o> CO CO CM

in o CO in ao CO r* VO CM 1 V* 1 CM in av ao av o vo px pH o av CM in CO CO ao av CD

r- 1 06 1 Ov •'C CO m o vo in o in VO

CM o m ao CO

m CO

pH

CO i h l -K l rH CM in in av CO ao r- 00 av pH CM CM CM CO CO CO CM CM

av 1 >1 1 CD OV in pH pH CO ro 00 ro m x* in VO av 00 r- vo o m o m o m o m o a> JZ — 1 • O'

4J 4J 1 pH pH CM CM CO CO xr in «0 CL.U-4 | N N s \ \ N N \ N u

01

— 1 m

O in o in o in o in <11

a i • • • • • • • • • > 06 o pH pH CM CM CO CO or xr < L0
Table

7.

Reverse

Torque

Ratios

for

20

in-lb

Torque

Increments

at

the

NBS

Site 11 CO CD CO CO 1 o i x • • • • 1 o | ON CD r~ i •H 1 CO CN CO w 1 C 1 m

(T3 1 • -C 1 ^ ro CO o

4-> 1 O' CO

0) 1 u | s*. CO CN o O 1 o CO CN E 11

f—i *"* *“* 11 VO 00 in r* 00 ^3* o VO CO «H O in Ov 1 1 (X VO in rH r*~ r- CN VO 00 crv O o r- i 1 ro sy CN CO CO N* O’ CO CN co CO in CO

O I O 1 CN

•H 1 • 1 ^ ro O CN r— VO CN o in in CO CN CO 1 i m 00 CN CO CO CO co CN co CN «er CO

f-i 1 CTV CD I • i 'N. CO CO in CD in r- CN CO CO CO 00 1 Ov CO C7\ CD CT> CD OV 00 00 CO av 00 ao 11 co r* Ov *T O' f—i CN CN r* r- ctv 00 P- CO VO CO o i ** . 4)1 1 X o o in ov KT CTv 00 in VO av CN •'T o ov p* i V 1 1 00 in CO CO »H CN CO in CO CO TT "«T *r H- | —* 1 l r* O 1 • CD I Ov CO 00 CO in CN o O VO o CTv CD CN H- in r- i r- 1 1 ^ CO CN CO CO CN *”• CN CO CO CO CN CO CO CN CO | CN

VO 11 ^ CO CD VO N* VO VO in CD CO r* CN in ov r—i CD I o 11 vO p» r— VO VO VO VO r* r** VO vO VO r* vo vO r~ i r*» 11 ON CN VO o CN CO ov m Ov VO CN 00 10 CN 1 1 X CO m vO ID CN o o OV CN O CN h 1 m o- CN CO CO O' CO CN CO CN CO TT VO CO 1 O 1 CO

VO 1 • i ^ CN in in CO in ”*T r- OV m o- CO O vO av 1 1 CN CN CN •"* f—i CN CN CO

*H | vO 1 • 1 <y\ r» in o 00 VO •'T CO crv CD VO Ov CD o 11

*cr in in in in •*r rr *T in in

m 11 o o CO CN CO o 4)1 1 X • | 1 Ov CN r- CO 00 CTv cyv in i 1 CN CO CN CN CN CN CO CN w l O 1i 49 i ! v rH 00 VO (T\ CD VO f—i X i rH r—i

r-t | (N | H 1 Nl CD in CN CT. CO VO 00 o 11 ro CN CN CO CO CN CN ro

0) ^a c

ct-h u 1 0/ 0 -Q O'

*0 rH CN CO in VO 00 Ov O CN ro in vO r* CD 1 14 o f—i f—i *—i z > X 1 < CO 1

10
Table

8.

Reverse

Torque

Ratios

for

the

Kingstowne,

VA

Site

11
Table

9.

Reverse

Torque

Ratios

for

20

in-lb

Torque

Increments

at

the

Kingstowne,

VA

Site

12
for the reverse torque ratios (in parentheses) are shown in the

last two rows of each table. In the second table for each site,

the data for the site are arranged by ranges of torque magnitudes

and averaged, in order to determine whether the reverse torque

ratio is sensitive to the magnitude of the torque (in the CPT the

friction ratio is sensitive to the magnitude of the tip resistance) .

Figures 1, 2, and 3 show grain size distributions for the

Groveton, VA, NBS, and Kingstowne, VA sites, respectively. No

grain size distribution was determined for the McLean, VA site,

but avalable data [1] indicate that D5 q

for the McLean site is

0.03mm and the material is silt (ML).

13
Figure 1* Grain Size Distribution for the Groveton, VA Site

14
Figure 2. Grain Size Distribution for the NBS Site.

15
Figure 3. Grain Size Distribution for the Kingstowne, VA Site.

16
3. ANALYSIS OF TEST RESULTS

Relation Between Reverse Torque Ratio and Particle Size:

Figure 4 shows a plot of average values of the reverse torque

ratio against D^q. The figure clearly illustrates that R decreases with increasing grain size. There are not enough data points

to suggest an equation for the relation between R and D50 , but

the figure shows that it will be possible to infer grain size

characteristics from reverse torque ratio after sufficient data

become available. A tentative correlation derived from the small

data sample available is:

R - 35 x , where R is in percent.

Sensitivity of Reverse Torque Ratio to Magnitude of Torque:

Figure 5 shows variation of R with t i2 for the various sites. The

figure indicates that R does not appear to be sensitive to the

magnitude of the downward torque.

Variability of Data:

The average coefficient of variation of the reverse torque ratios

was 0.18 for the Groveton, site, 0.19 for the McLean site, 0.24

for the NBS site, and 0.25 for the Kingstowne site. While this

variability is considerable, it is in part caused by the variability of the soils within the site, and it is within the range

of variabilities that would be anticipated for soil exploration

data.

17
60

55

50

45

40

35

i i i 'i—i—i—

rn ri i—i—i

1

1 m i i i—i—i

1

• Groveton (42)

Soil Type \ 1 \

Sand (SP) a Silt(ML) • Clay(CH)

(0) No. of data

points /

/

•^McLean (126)

X

Kinostowne(53)/^ - / A NBS(53) /

i"f i i i i i i 1

Mill 1 l 1 1 1 1 1 1 1 1 1 0 0.1 0.01 0.001

D50 , mm

4. Relation between D50 and Reverse Torque Ratio
t 12 . in-lb

Figure 5. Variation of R with t 12 .

19

4.

CONCLUSIONS

The helical probe test data presented in this report indicate

that there is a definite trend for the reverse torque ratio to

increase with decreasing average particle size. The variability

of the data is within the range that would be expected for soil

exploration data. The data sample in this study was not large

enough to allow recommending a relation between the reverse

torque ratio and the particle size characteristics that can be

used in the field, however the tentative relation suggested could

be used in pilot explorations.

5.

REFERENCES

[1] Yokel, F.Y., and Mayne, P.W., Helical Probe Tests for

Shallow Soil Exploration, NBSIR 86-3351, National Bureau

of Standards, Washington, D.C. January, 1986.

[2] ASTM Designation D2487-83, Standard Test Method for Classification of Soils for Engineering Purposes, American Society

for Testing and Materials, Vol. 4.08, 1985.

[3] ASTM Designation D1556-82, Standard Test Method for Density

of Soils In Place by the Sand Cone Method, American Society

for Testing and Materials, Vol. 4. 08, 1985.

6.

ACKNOWLEDGEMENT

The assistance of Paul W. Mayne and the Law Engineerring Testing

Company of McLean, VA in providing access to exploration sites

and test data is gratefully acknowledged.

21
NBS-114A (REV. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO. NBSIR 86-3423

2. Performing Organ. Report No. 3. Publ ication Date SEPTEMBER 1986

4. TITLE AND SUBTITLE

5 . Au^HO^( s^oung Chung and Felix Y. Yokel

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

10. SUPPLEMENTARY NOTES

|

i Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here) A helical test probe, developed by the National Bureau of

Standards for shallow soil exploration does not extract soil

samples from the ground. A study was therefore conducted to

determine whether the ratio of the torque required to extract the

Helical Test Probe to the torque required to advance the probe

(the reverse torque ratio) can be used to determine the average

grain size (

D

5 q

)

of the soil. On the basis of 274 test points in

sandy, silty, and clayey soils, it was concluded that the reverse

torque ratio decreases with increasing average grain size. The

relation between grain size and reverse torque ratio is apparently not sensitive to the magnitude of the torque required to

advance the probe.

12. KEY WORDS (Six to. twelve entries • alphabet / cal order; cn (utalJze only proper.names' and separate cc c

- tjonst ruction supervision; field test equipmeht; helical augers;

in situ measurements; penetration tests; soil investigation; test

procedures

.

13. availability 14. NO. OF

PRINTED PAGES

| Unlimited

] j For Official Distribution, Do Not Release to NTIS 27

Order From Superintendent of Documents, U.S. Government Printing Office, Washington. D.C. 20402. 15. Price

[£1 Order From National Technical Information Service (NTIS), Springfield, VA. 22161