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ASTM 2011 WorkshopJTG.1 A Perspective on Geotechnical Testing: The Details Matter John T. Germaine Massachusetts Institute of Technology Department of.

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Presentation on theme: "ASTM 2011 WorkshopJTG.1 A Perspective on Geotechnical Testing: The Details Matter John T. Germaine Massachusetts Institute of Technology Department of."— Presentation transcript:

1 ASTM 2011 WorkshopJTG.1 A Perspective on Geotechnical Testing: The Details Matter John T. Germaine Massachusetts Institute of Technology Department of Civil and Environmental Engineering

2 ASTM 2011 WorkshopJTG.2 The Question How well are we doing as a profession with regards to the characterization of soils?

3 ASTM 2011 WorkshopJTG.3 Outline Overview of soil testing industry Overview of soil testing industry Establishing quality control Establishing quality control Some example industry data Some example industry data Specific gravity Specific gravity Shrinkage limit Shrinkage limit Compaction Compaction Hydraulic conductivity Hydraulic conductivity Conclusions and recommendations Conclusions and recommendations

4 ASTM 2011 WorkshopJTG.4 Laboratory Testing Goals Diversity in test type Diversity in test type Broad range of materials Broad range of materials Accurate results Accurate results Timely delivery Timely delivery Profitability Profitability

5 ASTM 2011 WorkshopJTG.5 Testing Considerations Test methods Test methods Index Tests Index Tests Engineering Tests Engineering Tests No correct answer No correct answer Extreme variability of natural materials Extreme variability of natural materials Huge range in results Huge range in results Quality control concerns Quality control concerns

6 ASTM 2011 WorkshopJTG.6 Testing Organizations Commercial companies Commercial companies About 1200 About 1200 Commercial laboratories Commercial laboratories In-house engineering consultants In-house engineering consultants Small independent laboratories Small independent laboratories Government organizations Government organizations About 110 About 110 Academic research laboratories Academic research laboratories About 180 About 180

7 ASTM 2011 WorkshopJTG.7 Distribution of Tests Very informal poll Very informal poll Three large commercial Three large commercial One in-house engineering One in-house engineering Test numbers, not revenue Test numbers, not revenue

8 ASTM 2011 WorkshopJTG.8 Distribution Minus Index Significantly different distributions Significantly different distributions Large number of strength tests Large number of strength tests In-house QC type testing In-house QC type testing

9 ASTM 2011 WorkshopJTG.9 Quality Control Tools ISO Certification ISO Certification Management, documentation and training Management, documentation and training ASTM D3740 ASTM D3740 Guidance for technical, documentation and training requirements Guidance for technical, documentation and training requirements NICET NICET Certifies technician capabilties Certifies technician capabilties AMRL laboratory assessment AMRL laboratory assessment Certifies conformance to standard Certifies conformance to standard AMRL proficiency sample testing AMRL proficiency sample testing Sends out uniform subsamples Sends out uniform subsamples Evaluates collective test results Evaluates collective test results

10 ASTM 2011 WorkshopJTG.10 Documented Protocols Formal Standards Formal Standards ASTM ASTM AASHTO AASHTO BS BS In-house procedures In-house procedures Facilitate communication Facilitate communication Product uniformity Product uniformity Solidify professional practice Solidify professional practice Expand domain of expertise Expand domain of expertise Improve product quality Improve product quality

11 ASTM 2011 WorkshopJTG.11 Quality of a Test Method Precision and Bias Precision and Bias Bias: deviation relative to true value Bias: deviation relative to true value Precision: variation for given test method Precision: variation for given test method D18 standards have no Bias! D18 standards have no Bias! Quantities generally do not have a correct result Quantities generally do not have a correct result Use standard caveat statement in all standards Use standard caveat statement in all standards

12 ASTM 2011 WorkshopJTG.12 Quantifying Precision ASTM Standard E691 ASTM Standard E691 Round Robin or Interlaboratory Round Robin or Interlaboratory Ruggedness testing Ruggedness testing Impact of allowable variables Impact of allowable variables > 6 laboratories > 6 laboratories Triplicate testing in each lab Triplicate testing in each lab Acceptable range Acceptable range 2.8 x standard deviation 2.8 x standard deviation Repeatability for single operator Repeatability for single operator Reproducibility for between labs Reproducibility for between labs Limited to independent observations Limited to independent observations

13 ASTM 2011 WorkshopJTG.13 l: Classification and Index Simple equipment Simple equipment Considerable labor Considerable labor Technical skill and finesse Technical skill and finesse Difficult to check results Difficult to check results Rely on consistency and correlations Rely on consistency and correlations

14 ASTM 2011 WorkshopJTG.14 Example: Specific Gravity Test AMRL proficiency program AMRL proficiency program Method: ASTM D854 Method: ASTM D Laboratories 542 Laboratories Samples 157 and 158 Samples 157 and 158 Distributed uniform dry powder Distributed uniform dry powder One test on each sample One test on each sample

15 ASTM 2011 WorkshopJTG.15 AMRL Sample Specifics Sample 157 Sample 157 <20067 % <20067 % < 2 29 % < 2 29 % G s G s LL29 LL29 PI13 PI13 USCSCL USCSCL Sample 158 Sample 158 <20062 % <20062 % < 2 27 % < 2 27 % G s G s LL28 LL28 PI13 PI13 USCSCL USCSCL 2008 Proficiency Testing Program

16 ASTM 2011 WorkshopJTG.16 Specific Gravity Results Specific Gravity of Sample 158, (gm/cm 3 ) Specific Gravity of Sample 157, (gm/cm 3 ) Huge range in results Huge range in results Within laboratory correlation Within laboratory correlation Systematic error in procedure Systematic error in procedure 1995 study same variability 1995 study same variability

17 ASTM 2011 WorkshopJTG.17 Specific Gravity Results Specific Gravity, (gm/cm 3 ) Number of Observations Eliminate outliers Eliminate outliers Wide distribution Wide distribution Bias towards low values Bias towards low values Useful range 0.01 Useful range 0.01 ASTM ASTM Repeatability Repeatability Reproducibility Reproducibility

18 ASTM 2011 WorkshopJTG.18 Example: Shrinkage Limit Test Comparison of Wax and Hg Method Comparison of Wax and Hg Method AMRL proficiency program AMRL proficiency program Method: ASTM D4943 & D427 (old) Method: ASTM D4943 & D427 (old) About 50 Laboratories About 50 Laboratories Samples 159 & 160 and 161 & 162 Samples 159 & 160 and 161 & 162 Distributed uniform dry powder Distributed uniform dry powder One test on each sample One test on each sample

19 ASTM 2011 WorkshopJTG.19 AMRL Sample Specifics Sample 159 / 160 Sample 159 / 160 – <20089 / 83 % – < 2 39 / 37 % – G s / – LL43.0 / 43.2 – PI20.8 / 20.9 – USCSCL Sample 161 / 162 Sample 161 / 162 – <20065 / 46 % – < 2 24 / 20 % – G s /2.694 – LL24.8 / 23.7 – PI10.2 / 10.1 – USCSCL 2009 & 2010 Proficiency Testing Program

20 ASTM 2011 WorkshopJTG.20 Shrinkage Limit: Wax Method Huge range in results Huge range in results Within laboratory correlation Within laboratory correlation Systematic error in procedure Systematic error in procedure

21 ASTM 2011 WorkshopJTG.21 Shrinkage Limit: Wax Method Wide distribution Wide distribution Second year improvement Second year improvement Distribution skewed to higher values Distribution skewed to higher values

22 ASTM 2011 WorkshopJTG.22 Shrinkage Limit: Hg Method About the same range as Wax method About the same range as Wax method Within laboratory correlation Within laboratory correlation Systematic error in procedure Systematic error in procedure

23 ASTM 2011 WorkshopJTG.23 Shrinkage Limit: Hg Method Clear difference between each year Clear difference between each year Most labs in narrow range Most labs in narrow range Serious outliers Serious outliers

24 ASTM 2011 WorkshopJTG.24 Shrinkage Limit: Summary Wax gives lower values Wax gives lower values Wax method has more scatter Wax method has more scatter Average values capture subtle differences Average values capture subtle differences

25 ASTM 2011 WorkshopJTG.25 ll: Laboratory Compaction Simple equipment Simple equipment Calibration of automatic hammers Calibration of automatic hammers Energy transfer Energy transfer Material processing very important Material processing very important Technical skill Technical skill Interpretation of results Interpretation of results

26 ASTM 2011 WorkshopJTG.26 Example: Standard Proctor AMRL proficiency program AMRL proficiency program Method: ASTM D698 Method: ASTM D698 Samples 157 and 158 Samples 157 and Laboratories 963 Laboratories Report only opt and max Report only opt and max

27 ASTM 2011 WorkshopJTG.27 Compaction Results 157 Max. Dry Unit Weight, lbf/ft Max. Dry Unit Weight, lbf/ft Opt. Water Content, % 158 Opt. Water Content, % Water Content Water Content Weak correlation Weak correlation Processing issues Processing issues 157 higher 157 higher Serious outliers Serious outliers Unit Weight Unit Weight Better correlation Better correlation Technique differences Technique differences 157 lower 157 lower

28 ASTM 2011 WorkshopJTG.28 Compaction Results Max. Dry Unit Weight, lbf/ft 3 Opt. Water Content, % Number of Observations Outliers Removed Outliers Removed Water Content Water Content Broad distribution Broad distribution Subtle difference Subtle difference Unit Weight Unit Weight Narrow center band Narrow center band Clear shift in average Clear shift in average Symmetrical tails Symmetrical tails

29 ASTM 2011 WorkshopJTG.29 Compaction Results Considerable scatter Considerable scatter Clear outliers Clear outliers No trend No trend Unlikely results Unlikely results Impossible results Impossible results Water Content, % Dry Unit Weight, lbf/ft 3

30 ASTM 2011 WorkshopJTG.30 Compaction Results Dry Unit Weight, lbf/ft 3 Water Content, % opt =10.7 % opt =10.7 % max =122.6 lbf/ft 3 max =122.6 lbf/ft 3 AMRL Proficiency Sample 158 Field specification Field specification +/- 2 % c +/- 2 % c 92 % R.C. 92 % R.C. Field specification Field specification Including 2 Std. Dev. Including 2 Std. Dev.

31 ASTM 2011 WorkshopJTG.31 lll: Hydraulic Conductivity Widest range of any parameter Widest range of any parameter Extreme equipment demands Extreme equipment demands Little automation Little automation Expertise more than finesse Expertise more than finesse Attention to detail Attention to detail QC equipment QC equipment

32 ASTM 2011 WorkshopJTG.32 Example: Establishing Precision ASTM D5080 ASTM D5080 Craig Benson conducted study Craig Benson conducted study ISR ML, CL, and CH material ISR ML, CL, and CH material Provided compacted test specimens Provided compacted test specimens 12 laboratories 12 laboratories 3 tests per laboratory 3 tests per laboratory

33 ASTM 2011 WorkshopJTG.33 ISR Sample Specifics CH Sample CH Sample < % < % < 2 46 % < 2 46 % LL 60 LL 60 PI 39 PI 39 USCS CH USCS CH Vicksburg clay Vicksburg clay ML Sample ML Sample – < % – < 2 8 % – LL 27 – PI 4 – USCS ML – Vicksburg silt CL Sample CL Sample < % < % < 2 31 % < 2 31 % LL 33 LL 33 PI 14 PI 14 USCS CL USCS CL Annapolis clay Annapolis clay ASTM ISR managed 15,000 lbs of each soil NSF, FHWA, and private sponsorship Started Precision statements

34 ASTM 2011 WorkshopJTG.34 Hydraulic Conductivity Results Laboratory Number Hydraulic Conductivity, (cm/s) (10 -6 ) Variable Scatter with in labs Variable Scatter with in labs Two outlier labs Two outlier labs Some labs very consistent Some labs very consistent Log std. dev. fairly good Log std. dev. fairly good

35 ASTM 2011 WorkshopJTG.35 Hydraulic Conductivity Results Laboratory Number Hydraulic Conductivity, cm/s ML (x10-6) ML (x10-6) natural log natural log CL (x10-8) CL (x10-8) CH (x10-9) CH (x10-9) < < Avg. S. D.

36 ASTM 2011 WorkshopJTG.36 Hydraulic Conductivity Results Laboratory Number Hydraulic Conductivity, (cm/s) Log provides better representation Log provides better representation Equip. tuned to Equip. tuned to < one sign. digit < one sign. digit Real problems for low permeability Real problems for low permeability

37 ASTM 2011 WorkshopJTG.37 lV: Consolidation and Shear Significant advances in equipment Significant advances in equipment Extensive automation Extensive automation Technical expertise Technical expertise Sample quality and handling Sample quality and handling Testing decisions based on soil behavior Testing decisions based on soil behavior Essentially no precision data Essentially no precision data

38 ASTM 2011 WorkshopJTG.38 Conclusions QC tools are available QC tools are available Equipment adequate Equipment adequate Too much scatter Too much scatter Causes of scatter are not obvious Causes of scatter are not obvious No data for consolidation or strength No data for consolidation or strength Substantial room for improvement Substantial room for improvement

39 ASTM 2011 WorkshopJTG.39 Recommendations Formal protocols for every test Formal protocols for every test Technician training Technician training Consistency evaluation of results Consistency evaluation of results Reference material testing Reference material testing In-house databases In-house databases Participation in ASTM Participation in ASTM

40 ASTM 2011 WorkshopJTG.40 Acknowledgements Friends associated with ASTM Friends associated with ASTM Ron Holsinger; AMRL Ron Holsinger; AMRL Craig Benson; U of Wisconsin Craig Benson; U of Wisconsin


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