Cone Penetration Test (CPT) Quality Control (QC)
10/7/2013Gregg Drilling & Testing, Inc.Site Investigation ExpertsCone Penetration Test (CPT)Quality control (QC)Dr. Peter K. RobertsonWebinar #102013Robertson, 2013CPT Guide5th EditionDownload FREE copy .geologismiki.grRobertson& Cabal (Robertson)5th Edition2012Robertson, 20131
10/7/2013CPT Quality ControlTwo basic components: How to get good CPT (CPTu) data?– Consultants - Specifications (Standards)– Contractors - Equipment & procedures How to evaluate the data you have?– What to do with what you have?– Evaluate, correct and process dataRobertson, 2013Basic Cone ParametersFriction ratio (fs/qc)100 %Sleeve Frictionfs load/2 rhPore Pressureu2Tip Resistanceqc load/ r 2Robertson, 20132
10/7/2013CPT Quality ControlHow to get good CPT (CPTu) data? In general, CPT is very reliable, since it’s essentially operatorindependent. However, there are some things to ensureexcellent data– Consultants - Specifications (Standards)– Contractors - Equipment & proceduresRobertson, 2013StandardsThere are many Standards for CPT (& CPTu):– ISSMGE - (IRTP) 1999/2001– USA - ASTM D: 5778-12– European - CEN TC341 – CPT and CPTu(CEN/ISO 22476-1:2012)– Other National standards and codes– OffshoreRobertson, 20133
10/7/2013Standards - key elements Equipment– cone design, dimensional tolerances Calibration– accuracy (capacity – FSO) Procedures– zero load readings, saturation, push rate,temperature Corrections– unequal area effects - qc to qt ChecksRobertson, 2013Equipment Cone apex angle : 60 deg. Diameter : 35.7 mm for 10 cm2(up to 43.7mm for 15 cm2)– CEN: from 5 to 20 cm2 Friction sleeve area: 150 cm2 for10 cm2 (225 cm2 for 15 cm2) Prefered filter location for CPTu:behind cone (u2) Limits on dimensional tolerancesRobertson, 20134
10/7/2013Range in measurementsDimensionless SBT Chartfs/pa 1.0DimensionlessSANDChallenge to measure accuratevalues in soft soils butpenetrate dense soils that are 10x stronger!In most soft fine-grained soils:fs/pa 0.1qc 1 MPa (10 tsf)fs/pa 0.01CLAY1 kPa fs 50 kPaSoft fine-grained soilsModified from Robertson, 2010pa atmospheric pressure 0.1 MPa 1 tsfRobertson, 2013Example CPT in mixed soilsLargerange invalues!qc 60 MPafs 800 kPau2 -100 kPaqc 1 MPafs 5 kPau2 2,000 kPa3 orders ofmagnitudefor qc & fs6 -7 ordersofmagnitudefor u2Robertson, 20135
10/7/2013Example CPT in soft sedimentsIn upper 5m:qc 200 kPafs 5 kPaqc 0.5 MPa 500 kPafs 10 kPaIn very softsoils conesoften work atthe very lowend of themeasurementrangeRobertson, 2013Unequal end area effects on qcqt qc u2(1-a)a 0.60 to 0.85a tip net area ratio An/AcIn sands: qt qcIn very soft clays:correction to qt is importantCones should have high net area ratioa 0.8Robertson, 20136
10/7/2013Unequal end area effects on fsft fs – (u2Asb – u3Ast)/As10 cm2 cones As 150 cm215 cm2 cones As 225 cm2Equal end area cone, Asb Ast (ideally small)Pore pressure ratio, a u3/u2Typically: 0.50 a 0.80In very soft clays:Important to have equal end areasRobertson, 2013Error in fs due to end areasCompanycone size Asb(cm2)(mm2)AstAsb/Ast(mm2)(Lunne, 2006)FugroFugroAP 59343263214170150Dfs(kPa)u2 300 kPau3 210 kPa(Du2/s’v Error(fs 10 kPa)(fs/s’v 0.1)Soft soil30%20%16%57%37%6%In very soft fine-grained soils important to have equal end areasleeve with small area*ASTM requires equal end area sleevesRobertson, 20137
10/7/2013Robertson, 2013CalibrationMost modern cones havestrain gauge load cells thatare temperaturecompensated, withexcellent repeatability andlittle non linearity andhysteresis.Cones come in differentcapacities (FSO):Zero load drift critical in very soft soilsCommon high capacity cones Tip FSO 100 MPa(i.e 1,000 tsf)10 cm2 – 10 ton15 cm2 – 15 tonRobertson, 2013Load cell designQ FFQQSeparate load cellsSubtraction(better accuracy for fs)(slightly more robust)8
10/7/2013Robertson, 2013Application ClassesSome Standards specify Application ClassIRTP 2001Very soft soilsMixed soilsDense-stiff soilsRobertson, 2013Application ClassesISO 22476-1CEN TC341CPTuVery soft soilsCPTuCPTMixed soilsCPTuCPTDense-stiff soils9
10/7/2013Application Classes Application class 1: soft to very soft soil. Not for mixed soilprofiles with soft to dense layers. Tests can only be performed with CPTu. Application class 2: For mixed soil profiles with soft to denselayers, in terms of profiling, material identification and engineeringproperties, with limitations/restrictions in the soft layers. Penetrometer type(CPT or CPTu) depends on project requirements. Application class 3: For stiff and dense soils, in terms of profiling,material identification and engineering properties. Penetrometer type (CPTor CPTu) depends on project requirements.Robertson, 2013Accuracy Most strain gauge load cells have an accuracyof about 0.1% to 0.5% FSO 100 MPa (1,000 tsf) FSO capacity on tip (qc) accuracy of 0.1 to 0.5 MPa (i.e. 1 to 5 tsf)– Dense sand/stiff clay (with qc 10 MPa) – excellent accuracy( 1 to 5%)– Soft clay (qc 1 MPa) – need lower capacity (FSO) Key factor is zero load drift Zero load drift must not exceed expectedaccuracy (i.e. very small for soft soils)Robertson, 201310
10/7/2013Accuracy - Repeatability In general:– Tip (qt) is more accurate & repeatable than sleeve(fs) Prefer separate load cells to improve accuracy of fs Equal end area sleeves to minimize water effects on fs Check dimensional tolerance on sleeve– Tip (qt) is more accurate & repeatable than u2 Except in very soft fine-grained soils (where qc can bevery small and u2 can be very large) Potential loss of saturation in stiff dilative soils(negative values for u2)Robertson, 2013Repeatability - exampleLoss of saturation can produce ‘sluggish’ pore pressure responseRobertson, 201311
10/7/2013Repeatability of pore pressures data?Why is pore pressure data so complex and oftenlacks repeatability?– complex stress and strain field around cone– strongly dilative soils can produce negative pore pressuresat u2 locationPore pressure data can be very good in soft finegrained soils with high GWL– high positive pore pressures throughout– short depth to saturated soilsComplex distribution of pore pressuresModified from Campanella et al. 1985Robertson, 201312
10/7/2013Repeatability of fs?Sleeve friction measurements often consideredunreliable? use separate load cell design use equal end area sleeves (with small areas) check dimensional tolerance (avoid over sizedsleeve)Robertson, 2013Robertson, 2013Repeatabilityqt within20 kPafs within2 kPau2 within20 kPaVery soft, NCClayExcellent accuracy & repeatability is possible with good equipment & procedures13
10/7/2013Robertson, 2013Influence of oversized sleeveExcellentrepeatabilityin qt5 kPaExcellentrepeatabilityin u2NewOversized sleeveVery soft, NCClayOversized sleeve can produce more variable fs measurements due to variable wearCheck List (Contractors)equipment & proceduresRobertson, 201314
10/7/2013Zero load readings Ideally 3 zero load readings (with cone vertical):1. immediately before test (clean cone)2. immediately after test3. after test with cone cleaned Zero load drift immediately before and after test, i.e.readings 1 & 2):–used for interpretation of test results (captures impact of teston data – zero load correction) Zero load stability from before and after cleaning ofcone (i.e. readings 1 and 3):–measure of correct functioning of equipmentRobertson, 2013Causes of zero load drift? Most common cause:– Although most cones are temperaturecompensated, large temperature changes can causesmall zero load drift hot day ( 250C) to cool groundwater ( 50C) dense sand over soft clay– Ensure cone is powered for 15 mins before test– Take zero load reading before test at ground temp e.g. bucket of water to keep cone cool15
10/7/2013Consultants/clients Specify required standard (e.g. ASTM)– check for compliance Specify Application Class, if possible Supervise and ask for field check list– educate field supervisors Evaluate results in the field, if possible Check zero load drift and stability, if testingsoft soilsRobertson, 2013Client/consultant – Check ListRobertson, 201316
10/7/2013CPT Quality ControlHow to evaluate the data you have?– Evaluate, correct and process data CPeT-IT very useful software http://www.geologismiki.gr/– What to do with what you have? what to do if data is not ideal? examplesRobertson, 2013Evaluate data Check for:– Data spikes (e.g. rod breaks, etc.) – that should beremoved– Zero or negative readings (very soft soil withlarger zero load drift)– Overlay comparison to check consistency at site– Loss of saturation in pore pressure– Dissipation test(s) to estimate piezometric level(GWL)Robertson, 201317
10/7/2013Example data spikesData spike in qcData spike removedOccasional (single data) spike in one channel– can be due to electrical noise or depth triggering systemRobertson, 2013Example data spikesRaw dataCorrected dataAdd ‘hand auger’Data spikes in qcData spikes removedMissing data in fsNo missing dataRobertson, 201318
10/7/2013Example negative valuesRaw dataNegative fs valuesin very soft soilsData spikes in qcCorrected dataSmall values added to fs(1 or 2 kPa)Data spikes removedZero drift can cause some fs values to go negative in very soft soilRobertson, 2013Impact on interpretationNegative values makes SBTidentification (soil type)difficult, resulting in gaps ininterpretation.Gaps in interpretationRobertson, 201319
10/7/2013Impact on interpretationMissing gaps completedAdjust fs values to getcorrect SBT to fillmissing gaps often 1 or 2 kPaCheck interpretationvaluesRobertson, 2013WorkedExamplesCPeT-IT(see – petit)http://www.geologismiki.gr/John Th. IoannidesRobertson, 201320
10/7/2013Summary In most cases CPT data is reliable andrepresentative of ground conditions– e.g. much more reliable than SPT! Reduce chances of poor data by:– sound specification of standards– evaluate data in the field (train field staff)– use good data processing software (e.g. CPeT-IT)Robertson, 2013Questions?21
Cone Penetration Test (CPT) Quality control (QC) Dr. Peter K. Robertson Webinar #10 2013 Robertson, 2013 CPT Guide 5th Edition Download FREE copy from: www.greggdrilling.com www.cpt-robertson.com www.geologismiki.gr 5th Editi
cpt code:11740-2 94.14 cpt code:11750-2 541.06 cpt code:11755-2 123.03 cpt code:11760-2 128.26 cpt code:11762-2 571.07 cpt code:11765-2 581.10 cpt code:11770-2 861.67 cpt code:11771-2 1,092.11 cpt code:11772-2 1,703.29 cpt code:11900-2 56.09 cpt code:11901-2 162.31 cpt code:11920-2 116.23 cpt code
cpt code:11740-2 88.80 cpt code:11750-2 510.36 cpt code:11755-2 116.05 cpt code:11760-2 120.98 cpt code:11762-2 538.68 cpt code:11765-2 548.14 cpt code:11770-2 812.78 cpt code:11771-2 1,030.15 cpt code:11772-2 1,606.65 cpt code:11900-2 52.91 cpt code:11901-2 153.10 cpt code:11920-2 109.63 cpt code
Cone penetration test. CPTu Cone penetration test with pore pressure measurement – piezocone test. Cone The part of the cone penetrometer on which the cone resistance is measured. Cone penetrometer The assembly containing the cone, friction sleeve, and any other sensors, as well
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Assessment, Penetration Testing, Vulnerability Assessment, and Which Option is Ideal to Practice? Types of Penetration Testing: Types of Pen Testing, Black Box Penetration Testing. White Box Penetration Testing, Grey Box Penetration Testing, Areas of Penetration Testing. Penetration Testing Tools, Limitations of Penetration Testing, Conclusion.
CPT 93922 and CPT 93923 can be requested and reported only once for the upper extremities and once for the lower extremities. CPT 93922 and CPT 93923 should not be ordered on the same request nor billed together for the same date of service. CPT 93924 and CPT 93922 and/or CPT 93923 should not be ordered on the same request and should not be billed together for the same date
CPT 15823 Blepharoplasty, upper eyelid; with excessive skin weighting down lid CPT 19318. Reduction mammaplasty CPT 19324 Mammaplasty, augmentation; without prosthetic implant CPT 19325. Mammaplasty, augmentation; with prosthetic implant CPT 20550 Injection(s); single tendon sheath, or ligament, aponeurosis (e.g., plantar "fascia") CPT 20551
1 AWWA MANUAL M41 Chapter 1 General Information and History This manual provides the user with both technical and general information to aid in the design, specification, procurement, installation, and understanding of ductile-iron pipe.
