Dynamic Testing. Is it a good idea, or not? Garland Likins, P.E. Kuala Lumpur September 2013

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1 Dynamic Testing Is it a good idea, or not? Garland Likins, P.E. Kuala Lumpur September 2013 Pile structural integrity must be adequate Static Analysis Methods do not give accurate capacity 2 International Prediction Event Behaviour of Bored, CFA, and Driven Piles in Residual Soil, ISC 2 Experimental Site, 2003, by Viana da Fonseca and Santos This is WHY we test 2 1

2 Static testing is expensive Only a limited percentage of piles are tested on large projects Limited site variability coverage Limited coverage versus time On small projects, cost of static test might be more than cost of the piles. Formula developed for drop hammers on timber piles. Dynamic formula not much used in USA Committee widely discredited them and discouraged use (they recommended SLT) Better dynamic TESTING methods now available 10 year study Published Reference: ( ) Likins, G., Fellenius, B., Holtz, R., March, Pile Driving Formulas: Past and Present. Full-Scale Testing and Foundation Design; ASCE Geotechnical Special Publication No. 227; p

3 Dynamic Pile Monitoring Use Pile Driving Analyzer (PDA) to measure force and velocity during impact What can Dynamic Pile Testing do? Wave Equation GRLWEAP - prediction Dynamic Load Test Capacity EOD -BOR Capacity versus time setup/relax Case Method (closed form solution) CAPWAP ( signal matching ) icap (real time signal matching) Dynamic Monitoring Hammer Performance Driving Stresses Pile Integrity Find best way to install pile safely 3

4 7 Dynamic Testing - Advantages More information -at lower cost Supplement or replace static tests Optimize foundation design Capacity & distribution from CAPWAP Detect inefficient hammers Assure consistent performance vs time Know driving stresses (compression-tension) Detect pile damage Develop better installation procedures Lowers risk of foundation failures Safer foundation at lower costs USA experience: Lower cost than static load test One or two orders of magnitude less cost Test more piles Better site coverage Random tests as project proceeds Consulting rates (usually fee by day ) Codes and specifications all recognize and promote Bridges (AASHTO and State Dept. of Transportation) Buildings (IBC) ASTM D4945 Other (Army Corps of Engineers, ASCE, PDCA, DFI) State-of-practice and routine for most projects 4

5 PDCA LRFD AASHTO standard specifications Application: How many piles do we need? 40,000 kn column load, 2,000 kn pile ultimate capacity design load # piles S.F. per pile, kn needed /3.50 = 571 kn 70 dyn. formula No Test /2.75 = 727 kn 55 wave eqn /2.25 = 889 kn 45 dynamic test Test /2.00 = 1000 kn 40 Static (SLT) /1.90 = 1053 kn 38 SLT + dynamic 9 Better verification methods, and more testing, lower S.F. and therefore less cost. Number of piles required for example case AASHTO ASD AASHTO LRFD Eurocode Australia AS 2159 Dynamic formula N.A. Wave equation Dynamic test Max (2# or 2%) ODOT 44 (40) 2# (10#) 37 2% Dynamic test 100% Static test to 32 1# to 5# % 10% 51% savings savings 37 Dynamic test and Static test % dyn 1 static 10 5

6 "Myths" or concerns associated with PDA : 1. Black-box technology. 2. Test results can differs with different test systems 3. Lack of control of authenticity of data. Data altered by tester? 4. PDA test is not same as static test. It is an indirect test. Capacity is computed rather than measured. 5. Test result depends on skill of PDA engineers. No certifying body to assess skill level of PDA engineers Non-uniqueness of capacity result by various practitioners 6. Results are subjected to manipulation Engineers have little knowledge and no control of analysis Results interpreted to suit client rather than being correct 7. Non transparency in interpretation of test results Engineers cannot check analysis without software access Let us look at each one Myth 1 Black-box technology 268 reference papers on the PDI website on PDA 83 on CAPWAP 49 on GRLWEAP 33 on Correlation of Dynamic and Static testing Methods are fully published in papers and user manuals Numerous seminars provided worldwide since

7 Myth 2 Test results can differs with different test systems USA practice requires signal matching (e.g. CAPWAP) Pile Dynamics Sytem CAPWAP is proven reliable by numerous correlations More about this later Many CAPWAP correlations in literature by various authors CAPWAP is user friendly with many auto search features Other Systems Measurements: data quality Have seen good and bad Systems without signal matching ability (to be rejected) Not aware of any published correlation database Myth 3 Lack of control of authenticity of data. Data altered by tester? Date and Time stamp can NEVER be changed in PDI system Engineer should ALWAYS check the dates Compare with pile installation records Data (force and velocity) are encrypted cannot modify shape Calibrations of sensors shown on PDA-W plots Calibrations are now always shown on CAPWAP 2013 Calibrations cannot be changed on smart sensors Replay factors can be changed, but are shown Can request calibration sheets from test engineer Always review the calibration factors for sensors Strains ~ 95, PE acc~ 1000, PR acc~ 350 If doubts, can contact PDI to verify 7

8 Reports - ASTM D4945 date sensors Myth 4 PDA test is not same as static test. It is an indirect test. Capacity is computed rather than measured. USA practice requires signal matching (e.g. CAPWAP) CAPWAP is proven reliable by numerous correlations CW versus SLT combined (N=303) (80, 96, SW) Likins, G., Rausche, F., August Correlation of CAPWAP with Static Load Tests. Proceedings of the Seventh International Conference on the Application of StresswaveTheory to Piles 2004: PetalingJaya, Selangor, Malaysia; pg Many CAPWAP correlations in literature by various authors CW [kn] 40,000 30,000 20,000 10, ,000 20,000 30,000 40,000 SLT [kn] 8

9 Myth 4 PDA test is not same as static test. It is an indirect test. Capacity is computed rather than measured. USA practice requires signal matching (e.g. CAPWAP) CAPWAP is proven reliable by numerous correlations Distribution of CW / SLT Ratios (96&SW: N=226) 25.0% 20.0% Frequency 15.0% 10.0% 5.0% 0.0% under over 130 Ratio Distribution of CW / SLTmax Ratios (96&SW: N=179) 25.0% 20.0% Frequency 15.0% 10.0% 5.0% 0.0% under over 130 Ratio Myth 5 Test result depends on skill of PDA engineers. No certifying body to assess skill level of PDA engineers Non-uniqueness of capacity result by various practitioners Dynamic Measurement and Analysis Proficiency Test Certificate jointly issued by Pile Driving Contractors Association ( and Pile Dynamics, Inc. 9

10 Myth 5 Test result depends on skill of PDA engineers. No certifying body to assess skill level of PDA engineers Non-uniqueness of capacity result by various practitioners Dynamic Measurement and Analysis Proficiency Test Incentive to increase knowledge Better knowledge improves testing Knowledge reduce errors; lowers risk Required by many authorities Important to maintain-improve testing quality Growing concern about quality Certificate increases client s confidence 10

11 The Proficiency Test covers: Wave propagation theory PDA data interpretation PDA applications Data quality assessment Signal matching (e.g. CAPWAP) Test Format: Closed Book 60 question multiple-choice test, 90 minutes time limit, Minimal calculations. Suggested preparation and study resources: Attend Dynamic Foundation Testing Workshops, which are offered on a regular basis (For specific dates and location visit PDI calendar of events Powerpoint presentations from PDA Workshops Appendix A from PDA manual "Helpful Hints" appendix from PDA manual Background information from the CAPWAP manual Practice PDA "Example Data" (many are discussed in a PDA manual appendix) 11

12 Rank Required Score Suggested Validity Expert % Lifetime Master 85-92% 5 years Advanced 75-84% 4 years Intermediate 65-74% 3 years Basic 55-64% 2 years Provisional 45-54%* 1 year* *Provisional level expires 1 year from original test date Specifying agency can set their own Minimum RANK Validity Term SORT Expert > 93% Master > 85% Advanced > 75% Intermediate > 65% Basic > 55% Provisional > 45% 12

13 Certificate not a certification 13

14 Myth 5 Test result depends on skill of PDA engineers. No certifying body to assess skill level of PDA engineers Non-uniqueness of capacity result by various practitioners Dynamic Measurement and Analysis Proficiency Test All project owners (authorities, developers) or their engineering representative should REQUIREthe testing engineer to pass their minimum standard of knowledge, and hold this certificate. Myth 5 Test result depends on skill of PDA engineers. No certifying body to assess skill level of PDA engineers Non-uniqueness of capacity result by various practitioners From any given pile test: Pile model is made automatically in CAPWAP Minor adjustment to displacement curve to match set (minor effect on capacity) CAPWAP is a minimization exercise: only ONE solution for soil model having absolute lowest Match Quality (MQ) Question is how diligent test engineer is to get low MQ Many automatic search options to assist getting best MQ 14

15 Myth 5 Test result depends on skill of PDA engineers. No certifying body to assess skill level of PDA engineers Non-uniqueness of capacity result by various practitioners CAPWAP results of knowledgeable testers have little variation Discuss in more detail Pipe in Silt H in Sand COV 5% COV 6% Long pipe, very sensitive clay Pipe to weak crushing sandstone COV 13% COV 14% Variation of CAPWAP Results as a Function of the Operator by Fellenius, Third Int l Conf. on Application of Stress-wave Theory to Piles,

16 Tangent Butler-Hoy Corps of Engr. Static Load Test Evaluations Brinch Hansen 90% Fuller-Hoy Mazurkiewicz Housel DeBeer Shen-Nu Range 0.73 (DeBeer) to 1.42 (Chin) COV 18.4% Chin-Kondner Brinch Hansen 80% Davisson Q/Qavg Duzceer & Saglamar, Evaluation of Pile Load Test Results DFI Conference - Nice France, 2002 CAPWAPmight have more uniqueresult than Static Load Test interpretation! 16

17 CAPWAP - Results SLT +20% -20% CAPWAP Case Method CAPWAP 33 CAPWAP - Results SLT +20% -20% Unique solution? Yes - if you Case CAPWAP pursue to get the absolute minimum Method CAPWAP error in Match Quality. But does it really matter? No since solutions are generally all similar (within reasonable tolerance) and different blows may give slightly different answers Static test interpretation also is not unique! 34 17

18 Myth 6 Results are subjected to manipulation Engineers have little knowledge and no control of analysis Results interpreted to suit client rather than being correct icap is a quick signal matching program for uniform driven piles that produces a unique result for any set of data. No user control of any kind to get solution. The results are independent of users Likins, G. E., Liang, L., Hyatt, T., September Development of Automatic Signal Matching Procedure -icap. Proceedings from Testing and Design Methods for Deep Foundations; IS-Kanazawa: Kanazawa, Japan; icap example Quick icap CAPWAP Ru 493 kips 506 kips CSC 3.15 ksi 3.17 ksi TSC 0.22 ksi 0.17 ksi MQ 2.12 MQ

19 icapon PDA icap performance (7/20/2010) 19

20 Myth 6 Results are subjected to manipulation Engineers have little knowledge and no control of analysis Results interpreted to suit client rather than being correct Problem is only when the contractor is the client and pressures the tester. Avoid this problem by having the authority or his representative hire the tester directly. Do not give contract for testing to contractor. Likins, G. E., Liang, L., Hyatt, T., September Development of Automatic Signal Matching Procedure -icap. Proceedings from Testing and Design Methods for Deep Foundations; IS-Kanazawa: Kanazawa, Japan; Myth 7 Non transparency in interpretation of test results Engineers cannot check analysis without software access Can understand basic principles and evaluate basic data quality Read reports Look at the data curves presented ASTM D4945 requires plots of data for each test pile Verify time stamps A PDA-Viewer program is available Require the PDA data file (*.W01) from test company 20

21 Myth 7 Non transparency in interpretation of test results Engineers cannot check analysis without software access Can understand basic principles and evaluate basic data quality Read reports Look at the data curves presented Verify time stamps A PDA-Viewer program is available Require the PDA data file (*.W01) from test company If any doubts, seek second opinion reviewfrom third party Nominal fee to render opinion Total cost including review significantly less than SLT. Good data, Good results 21

22 Marginal data, Marginal results Questionable data, Bad results 22

23 Very Bad data, Totally unreliable results Myth 7 Non transparency in interpretation of test results Engineers cannot check analysis without software access A PDA-Viewer program is available A CAPWAP Review program is now available Available for rent at a nominal fee 23

24 CAPWAP 2013 version CAPWAP 2013 REVIEW version 24

25 CAPWAP CAPWAP REVIEW Read only Manual only No Printout CAPWAP 2013 version CAPWAP REVIEW DEMO program to learn basic operation 25

26 Myth 7 Non transparency in interpretation of test results Engineers cannot check analysis without software access A PDA-Viewer program is available A CAPWAP Review program is now available Available for rent at a nominal fee If any doubts, seek second opinion review from third party Send data files (*.W01 or *.CWW) to third party PDI can digitize force and velocity plots versus time Nominal fee to render opinion Total cost including review significantly less than SLT. Can also request review of any report (random spot check) USA example On design/build FDOT projects, FDOT requires a Test Pile per 70 meters of bridge length with a minimum of two Test Piles per structure. Every Test Pile monitored by testing specialist is peer reviewed by FDOT technical specialist. Additional field testing up to 10% of production piles is commonly performed by testing specialist and peer reviewed by FDOT technical specialist. More testing if failures or problems detected. FDOT technical specialist is usually a different testing specialist, but sometimes is an FDOT engineer trained in dynamic pile testing. Sometimes both review. For small conventional FDOT projects, FDOT does more Test Piles (one pile per bent). Testing is done by testing specialist and peer reviewed by FDOT technical specialist. Additional restrike testing if installation has unusual behavior. Projects or bents with 100% testing due to LRFD advantage. 26

27 Myth 7 Non transparency in interpretation of test results Engineers cannot check analysis without software access If any doubts, can seek review from third party Nominal fee to render opinion Total cost including review significantly less than SLT. Second opinion may confirm or disagree with original finding Data good, capacity higher: no problem Small differences should be accepted Myth 7 Non transparency in interpretation of test results Engineers cannot check analysis without software access What if second opinion confirms major disagreement? Poor data quality, Interpretation of results 27

28 Myth 7 Non transparency in interpretation of test results Engineers cannot check analysis without software access Suggested actions for MAJOR DISAGREEMENT Temporarily suspend test company from project Perhaps 3 month suspension (first offense), or Perhaps 6 month suspension (second offense), or 12 month suspension (third or more offense), suspend means do not accept report by that tester AND -Require they attend a training class before resuming Summary When properly performed, dynamic testing is reliable With highly significant cost savings and extra information available, dynamic testing is highly beneficial to reduce risk Place contract for testing direct to the tester, and not through the contractor, or plan to have third party review Authorities and project developers have the power to enforce and insure dynamic testing results are reliable. 28

29 Recommendations for Dynamic Testing: PDA provides information not available by SLT stresses, integrity, hammer energy,. set-up CAPWAP has large proven correlation database icap now available for on-site signal matching Dynamic Testing is orders of magnitude less cost than SLT Allows more testing which reduces risk Disadvantages and concerns have been addressed Tools are available to assure results are reliable PDA-Viewer & CAPWAP-Review Third Party independent reviews Recommendations to assure quality of results: Require tester to attain some rank on Proficiency Test Understand the principles from workshops. Evaluate: data quality, confirm time stamp, sensor information Signal Matching by CAPWAP or icap is required Assess the solution by CAPWAP-Reviewer software Submit questionable results to third party review. even with review fee, is much less cost than SLT Submit random reports for third party review - spot check Discipline tester if results contain major errors (suspensions, require more training) 29