Tel +61 7 5471 2640 John Simmons Pty Ltd ABN 64 069 204 ... · Figure 1 is a general view of the LDSM. The bottom section of the shear box is displaced, and slides on a customised

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MEMO Date: 9 October 2014 Ref: 7505 / 7400 / 576-1 To: Trilab Pty Ltd Attention: Col Purvis, Chris Channon, Chris Park, James Russell Copy: Professor Stephen Fityus, The University of Newcastle From: John Simmons ___________________________________________________________________________ Subject: INTERLAB PROFICIENCY TESTING REPORT: STOCKTON BEACH SAND PARTICLE SIZE DISTRIBUTION, PARTICLE SPECIFIC DENSITY, DRY SHEAR STRENGTH: DIRECT SHEAR APPARATUS 1. Introduction The University of Newcastle has used locally available, well sorted Stockton Beach Sand as a reference material for many research projects over a considerable period of time. Ajalloeian et.al (1996) published a compilation of properties which has formed the basis for later comparison and calibration tests. Over the period 2012 to 2014, as part of a research project funded by the Australian Coal Association Research Program (ACARP), a large direct shear machine (LDSM) was designed, constructed, and operated for measuring the shear strength of coal mine spoil materials. Stockton Beach Sand was used for a number of calibration tests, including comparisons of three different shear box sizes of 300mm x 300mm and 720mm x 720mm (LDSM). During 2014 some variations in LDSM test results were obtained when a different operator undertook repeat calibration tests on Stockton Beach Sand. Because the LDSM design for application of shear deformation differs in some respects from typical direct shear apparatus, it was decided to seek an independent strength measurement to provide certainty about which of the two LDSM calibration tests was most accurate. Trilab Pty Ltd operates a large NATA-accredited testing facility in Brisbane, and was approached to undertake independent testing of Stockton Beach Sand as an inter-laboratory proficiency testing exercise. This report summarises the Trilab and University of Newcastle (UN) results for:

Particle size distribution (PSD);

Particle specific density (Gs);

Direct shear tests on sand placed as loosely as possible.

SHERWOOD GEOTECHNICAL AND RESEARCH SERVICES

7505-7400-Trilab-sgl14576-1.docx Page 2

2. Summary Findings Particle Size Distribution The Trilab and UN PSD results are significantly different. The Trilab tests were carried out under a system of accreditation which is designed to demonstrate traceability of methodology and calibrations to reference standards. The UN PSD data was obtained some time ago. It is recommended that UN carry out PSD measurement for a representative sample of the current batch of sand, and for each batch of sand supplied in future. Particle Specific Density The Trilab and UN results are in very close agreement. No formal identification of “correct” parameter values has been made, and for practical engineering purposes the Trilab and UN results are considered to be equivalent. Direct Shear Strength For interlab comparison purposes, only the Trilab peak direct shear strength data were considered. Further discussion of the Trilab residual shear strength data are provided below. The Trilab and UN LDSM peak strength interpretations are generally in close agreement, with a greater discrepancy between the UN LDSM and UN Prolab envelopes. This discrepancy may be due to differences in specimen preparation and initial setup, which is a matter for further evaluation by UN. On the other hand, the relationships between initial density and friction angle are somewhat scattered but suggest a trend that is consistent between the Ajalloeian et.al. (1996), UN Prolab, and Trilab results, with the UN LDSM results being slightly higher. If this trend is valid, it may reflect differences in scale and/or differences in the method of application of shear loading to the UN LDSM versus the “traditional” direct shear apparatus. 3. Trilab Testing A 20L bucket of Stockton Beach Sand was sampled from the UN laboratory stockpile and forwarded to Trilab together with a test request sheet prepared by SGRS. Relevant Australian Standard methods were followed, and the direct shear tests were carried out in a 100mm x 100mm shear box. Copies of Trilab PSD, Gs, and Direct Shear Strength test certificates are included in Appendix A. The Trilab results describe both peak and residual strength states. While the interpretation of peak state is clear, residual strength is a term that should preferably be reserved for cohesive materials with fully-developed shear surfaces. The term “constant-volume” abbreviated as “cv” is preferably reserved for cohesionless material such as Stockton Beach Sand. Trilab quoted relative shear displacement criteria for “residual” strength. The plots of vertical displacement and shear stress vs relative shear displacement could not easily be re-interpreted in terms of a “cv” state, particularly since the different colours for the four different normal stress points did not seem to be consistent with the usual expectation of vertical displacement at increasing levels of normal stress.



While Trilab correctly quoted the best-fit linear envelopes to the peak and “residual” states, each had a negative effective cohesion intercept. This is not an issue for informed interpretation of the data, and is possibly a consequence of the initially loose placement and subsequent normal stress levels for the four data points. 4. University of Newcastle Testing 4.1 Apparatus Particle size distribution at UN is carried out by sieving (dry or wet) or by using a semi-automated particle sizer. Ajalloeian et.al (1996) did not state the method(s) used for PSD or for particle specific density data generation. For inter-laboratory proficiency purposes, a Micromeritics gas pycnometer was used. Direct shear equipment includes multiple conventional 60mm x 60mm apparatuses and a Prolab 300mm x 300mm apparatus. Tests were carried out in the Prolab 300mm x 300mm apparatus as part of the calibration and scale-comparison activities for the development of the LDSM. Test results reported by Ajalloeian et.al. (1996) had previously been generated using a 60mm x 60mm apparatus. Figure 1 is a general view of the LDSM. The bottom section of the shear box is displaced, and slides on a customised PTFE/stainless steel bearing sheet. The lines of application of the shear force actuators and load cells are both not co-planar with the shear plane formed by the separation between the lower and upper sections of the shear box. The three normal force actuators are interconnected and controlled to maintain the resultant force at the centroid of the top cap. The LDSM was designed to apply normal stresses of up to 4.5MPa in order to simulate stress conditions within very high coal mine spoil dumps. Despite the non-coplanar shear forces potentially inducing a moment across the shear plane, minimal rotation of the top cap has been a feature of all tests undertaken to date. 4.2 Particle Size Distribution and Particle Specific Density The particle size distribution information in Ajalloeian et.al. (1996) is widely referenced in UN research projects and was adopted for this report. A copy of this paper is provided in Appendix B. Figure 2 is a comparison of the Trilab and UN data. While both results qualify as well-sorted (or poorly graded) sand, there is a significant difference between the two results with the Trilab distribution ranging from 5% to 20% greater at any given sieve size. Trilab reported the particle specific density as Gs = 2.64. Ajalloeian et.al. (1996) quoted the particle specific density as Gs = 2.65, whereas UN tests carried out using the UN gas pycnometer reported Gs = 2.66 and certificates are included in Appendix B. 4.3 Direct Shear Tests All of the direct shear tests were carried out on dry sand. Results of all of the Trilab and UN tests on loose-placed sand are shown in Table 1. These results consider only the maximum shear stress interpreted for each normal stress point. The Trilab test certificate did not report the initial densities of the four normal stress points reported, so the nominal density from the certificate was allocated to each stress point.



Envelopes to the results of tests carried out in the UN LDSM were fitted at “low stress range” (0 to 1500 kPa) and “high stress” (0 to 3500 kPa). The UN Prolab shear box strength envelope was fitted to the stress range 0 to 1100 kPa). Fitted envelopes are shown in Figure 3. 5. Commentary One of the purposes of inter-laboratory proficiency testing is to demonstrate consistency of results between different operators and apparatus. In this case the particle specific density was consistent between laboratories and methods within the range 2.64 to 2.66, which is, in the opinion of the undersigned and not based on rigorous calculation, consistent with the likely measurement uncertainties for the test methods. The differences in reported particle size distributions may be attributable to several causes, but in the opinion of the undersigned the UN results should be checked and if necessary updated. Different physical processes may be involved in sieving versus an optics-based sizer technique, and this may have influenced the results. Alternatively, the sand specimens tested by Ajalloeian et.al. (1996) may be a different sample from that used in the UN LDSM and UN Prolab calibration tests, and as-supplied to Trilab. The agreement between the Trilab and UN peak strength interpretations is, in practical terms, very close except for the UN Prolab apparatus. This may be due to specimen preparation conditions, because some preparation inconsistencies in mass and volume were reported. However, Figure 4 shows all the direct shear test results plotted as calculated friction angle versus initial density. The relationships between initial density and friction angle are somewhat scattered but suggest a trend that is consistent between the Ajalloeian et.al. (1996), UN Prolab, and Trilab results, but with the UN LDSM results being slightly higher than this trend. If valid, the difference in density-strength trend may reflect differences in scale and/or differences in the method of application of shear loading to the LDSM versus the “traditional” direct shear apparatus. Please contact me to discuss any aspect of this report in further detail. Best wishes

John V Simmons Principal Sherwood Geotechnical and Research Services Appended: A. Trilab Test Certificates B. University of Newcastle Information: Ajalloeian et.al. (1996), gas pycnometer test certificates



Figure 1 LDSM showing split shear box and normal and shear load paths

Figure 2 Comparison of Trilab and UN particle size distribution results

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100

% P

assi

ng

Particle Size (mm)

Trilab = dry sieving, UN = averaged of multiple sieving/sizer tests



Table 1 All Direct Shear Test Results for Peak Strength

TEST σ'

(kPa)

(kPa) /σ' ’

(deg) Rate

(mm/min) Ht (m) Vol

(m3) Mass (kg)

Bulk Density (t/m3)

Trilab 100mm 99.7 59.2 0.594 30.7 0.01 - - - 1.53

Trilab 100mm 199.5 122.6 0.615 31.6 0.01 - - - 1.53

Trilab 100mm 300.1 180.6 0.602 31.0 0.01 - - - 1.53

Trilab 100mm 500.0 306.1 0.612 31.5 0.01 - - - 1.53

UN LDSM 720mm 843 515 0.61 31.4 3 0.572 0.297 445.3 1.502

UN LDSM 720mm 1036 622 0.60 31.0 3 0.58 0.301 450 1.497

UN LDSM 720mm 627 383 0.61 31.4 3 0.568 0.294 441.3 1.499

UN LDSM 720mm 1247 772 0.62 31.8 3 0.58 0.301 454.4 1.511

UN LDSM 720mm 1460 884 0.61 31.2 3 0.575 0.298 448 1.503

UN LDSM 720mm 3379 2021 0.60 30.9 3 0.578 0.300 443 1.478

UN LDSM 720mm 2487 1518 0.61 31.4 5 0.57 0.295 444.1 1.503

UN LDSM 720mm 1823 1072 0.59 30.5 5 0.57 0.295 438 1.482

UN Prolab 300mm 877 492 0.56 29.3 3 0.18 0.016 23.83 1.471

UN Prolab 300mm 1010 583 0.58 30.0 3 0.181 0.016 24.21 1.486

UN Prolab 300mm 1008 568 0.56 29.4 3 0.178 0.016 23.85 1.489

UN Prolab 300mm 504 275 0.55 28.6 3 0.176 0.016 23.23 1.467

UN Prolab 300mm 703 403 0.57 29.8 3 0.18 0.016 24.12 1.489

UN Prolab 300mm 1108.3 612 0.55 28.9 3 0.183 0.016 24.2 1.469

UN Prolab 300mm 603.9 341 0.56 29.5 3 0.179 0.016 23.8 1.477

UN (1996) 60mm 106 65 0.55 31.5 0.435 - - - 1.540

UN (1996) 60mm 37.9 22.2 0.59 30.4 0.435 - - - 1.523

UN (1996) 60mm 174.1 106.4 0.55 31.4 0.435 - - - 1.522

UN (1996) 60mm 242.2 149.2 0.55 31.6 0.435 - - - 1.526

UN (1996) 60mm 378.5 231.9 0.55 31.5 0.435 - - - 1.521



Figure 3 UN LDSM and Prolab direct shear peak strength envelope interpretations

Figure 4 Comparison of Trilab and UN direct shear density-strength interpretations

y = 0.6086x + 0.7788

y = 0.5662x ‐ 2.5185

y = 0.5973x + 10.285

0

500

1000

1500

2000

2500

0 500 1000 1500 2000 2500 3000 3500 4000

Shear Stress (kPa)

Normal Stress (kPa)

LDSM (low stress range)

PROLAB 300mm (low stress range)

LDSM to high stress

LDSM LOW STRESS RANGE RESULT:

c' = 0.8 kPa, ' = 31.3°, or friction only (c' = 0) ' = 31.4°

PROLAB LOW STRESS RANGE RESULT:

c' = ‐2.51 kPa, ' = 29.5°, or friction only (c' = 0) ' = 29.4°

LDSM TO HIGH STRESS RANGE:

c' = 10.3 kPa, ' = 30.8°, or friction only (c' = 0) ' = 31.1°

28.5

29.0

29.5

30.0

30.5

31.0

31.5

32.0

1.46 1.48 1.50 1.52 1.54 1.56

Friction Angle (deg)

Initial Dry Density (t/m3)

Trilab 100mm

UN LDSM 720mm

UN Prolab 300mm

UN Ajalloeian et.al. (1996) 60mm


APPENDIX A

Trilab Test Certificates

Brisbane

346A Bilsen Road,

Geebung

QLD 4034

Ph: +61 7 3265 5656

Perth

2 Kimmer Place,

Queens Park

WA 6107

Ph: +61 8 9258 8323Soil Rock Calibration

chrispgo22

James

Client Report No.

Project Test Date

Report Date

Sample No. 14080737 - - - - - -

Client ID 20L Bucket - - - - - -

Depth (m) Not Supplied - - - - - -

Moisture (%) 0.1 - - - - - -

AS SIEVE SIZE

(mm)

150 - - - - - -

75 - - - - - -

53 - - - - - -

37.5 - - - - - -

26.5 - - - - - -

19 - - - - - -

9.5 - - - - - -

4.75 - - - - - -

2.36 - - - - - -

1.18 - - - - - -

0.600 100 - - - - - -

0.425 90 - - - - - -

0.300 41 - - - - - -

0.150 0 - - - - - -

0.075 0 - - - - - -

NOTES/REMARKS:

Sample/s supplied by the client Page 1 of 1 REP01102

Laboratory No. 9926

PERCENT PASSING

Trilab Pty Ltd ABN 25 065 630 506

Reference should be made to Trilab's “Standard Terms and Conditions of Business” for further details.

The results of calibrations and tests performed apply only to the specific instrument or sample at the time of test unless otherwise clearly stated.

PARTICLE SIZE DISTRIBUTION TEST REPORTTest Method: AS 1289 3.6.1, 2.1.1

Sherwood Geotechnical and Research

Services

C20019 LDSM Calibration Checks

14080737-G

11/09/2014

8/9/14-11/9/14

Authorised Signatory

C. Channon

Accredited for compliance with ISO/IEC 17025. The results of the tests, calibrations, and/or measurements included in

this document are traceable to Australian/National Standards.

Tested at Trilab Brisbane Laboratory.

ACCURATE QUALITY RESULTS FOR TOMORROW'S ENGINEERING

Brisbane

346A Bilsen Road,

Geebung

QLD 4034

Ph: +61 7 3265 5656

Perth

2 Kimmer Place,

Queens Park

WA 6107


chrispgo22

James

Client Report No.

Project Test Date

Report Date

Sample No. 14080737 - - - - - -

Client ID 20L Bucket - - - - - -

Depth (m) Not Supplied - - - - - -

Soil Particle

Density (t/m³)

(-2.36mm)

2.64 - - - - - -

NOTES/REMARKS:

Sample/s supplied by the client Page 1 of 1 REP04603

Laboratory No. 9926




SOIL PARTICLE DENSITY TEST REPORTTest Method: AS 1289 3.5.1

Sherwood Geotechnical and Research

Services


14080737-SG

11/09/2014

10/09/2014


C. Channon

Accredited for compliance with ISO/IEC 17025. The results of the tests, calibrations, and/or measurements included in this

document are traceable to Australian/National Standards.



Brisbane

346A Bilsen Road,

Geebung

QLD 4034

Ph: +61 7 3265 5656

Perth

2 Kimmer Place,

Queens Park

WA 6107

Ph: +61 8 9258 8323Soil Rock CalibrationJames 5758

Client Report No.

Project Test Date

Report Date

Client ID

Description Sample Type

Failure Criteria

Notes/Remarks: Please review the results if the Cohesion is above 2 kPa when plotted with a line of best fitNote: Area correction based on square sample equation.

Graph not to scale Sample/s supplied by the client Page 1 of 4 REP03302

Laboratory No. 9926

DIRECT SHEAR TEST REPORT

Residual: Stages 1 & 2 @ 2.5mm: Stages 3 & 4 @ 4mm Displacement

Test Method: AS 1289.6.2.2 / ASTM D5607

10/09/2014

5/09/2014

14080737- DS

Not SuppliedDepth (m)

Sherwood Geotechnical and Research Services


20L Bucket


Four individual soil specimens -

remoulded as requested by the client.SAND - brown




C. Channon


C. Channon


C. Channon


C. Channon

99.7 kPa

199.5 kPa

300.1 kPa

0

50

100

150

200

250

300

350

0 2 4 6 8 10 12

Sh

ear

Str

ess (

kP

a)

Relative Displacement (mm)

Shear Stress/Displacement Plot

99.7 kPa 199.5 kPa 300.1 kPa

-0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1

0 0.1 0.2

0 2 4 6 8 10 12

Vert

ical D

isp

lacem

en

t (m

m)

Relative Displacement (mm)

Vertical Displacement/Relative Displacement Plot





Brisbane

346A Bilsen Road,

Geebung

QLD 4034

Ph: +61 7 3265 5656

Perth

2 Kimmer Place,

Queens Park

WA 6107


Client Report No.

Project Test Date

Report Date

Client ID


Failure Criteria

31.3 -22.3 R2

Specimen Condition Shear Stress (kPa)

Specimen Dimensions (mm)

Rate of Strain (mm/min)

Initial Moisture Content (%)

Initial Wet Density(t/m3) 286.5



Laboratory No. 9926

10/09/2014

20L Bucket Depth (m) Not Supplied

SAND - brown Four individual soil specimens -

remoulded as requested by the client.



Shear Angle (o) 0.992

0.1

100*100

Cohesion (kPa)

As Received Normal Stress (kPa)


Residual: Stages 1 & 2 @ 2.5mm: Stages 3 & 4 @ 4mm Displacement


Sherwood Geotechnical and Research Services 14080737- DS

C20019 LDSM Calibration Checks 5/09/2014


Stage 3 159.4

81.6

51.8

300.1

199.5

99.7

0.010

1.53 500.0Stage 4

Stage 2

Stage 1


C. Channon


C. Channon


C. Channon


C. Channon

0

100

200

300

400

0 100 200 300 400 500 600

Sh

ear

Str

ess (

kP

a)

Normal Stress (kPa)

Residual - Normal Stress vs Shear Stress





Brisbane

346A Bilsen Road,

Geebung

QLD 4034

Ph: +61 7 3265 5656

Perth

2 Kimmer Place,

Queens Park

WA 6107


Client Report No.

Project Test Date

Report Date

Client ID


Failure Criteria

31.6 -1.8 R2

Specimen Condition Shear Stress (kPa)

Specimen Dimensions (mm)

Rate of Strain (mm/min)

Initial Moisture Content (%)

Initial Wet Density(t/m3) 306.1



Laboratory No. 9926


122.6

59.2

300.1

199.5

99.7

180.6


1.53 500.0Stage 4

20L Bucket Depth (m) Not Supplied



Peak


Sherwood Geotechnical and Research Services 14080737- DS

Stage 3

As Received

Stage 20.010

0.1

Shear Angle (o)

100*100

1.000

SAND - brown Four individual soil specimens -

remoulded as requested by the client.

Stage 1

Cohesion (kPa)

Normal Stress (kPa)

C20019 LDSM Calibration Checks 5/09/2014

10/09/2014


C. Channon


C. Channon


C. Channon


C. Channon

0

100

200

300

400

0 100 200 300 400 500 600

Sh

ear

Str

ess (

kP

a)

Normal Stress (kPa)

Peak - Normal Stress vs Shear Stress






APPENDIX B

University of Newcastle Information: Ajalloeian et.al. (1996) gas pycnometer test certificates

Documents

Tel +61 7 5471 2640 John Simmons Pty Ltd ABN 64 069 204 ... · Figure 1 is a general view of the LDSM. The bottom section of the shear box is displaced, and slides on a customised