Deep Foundation Testing, Multiple Topics Brent Robinson, Ph.D., P.E. www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Deep Foundation Testing, Multiple Topics • PDA/CAPWAP applied to large diameter piles versus small diameter piles • PDA/CAPWAP challenges for open ended piles • Thermal Integrity Profiling (TIP) • How to interpret CSL results for acceptance of shafts; when to remediate/repair/replace, etc. based on test results • Determining capacity and assessing integrity of a damaged pile or drilled shaft through dynamic testing • SPT Analyzer best methods for determining energy transfer of automatic hammers www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Driven--Large vs small diameter • Not a lot of direct comparisons • Might need different hammers • Sites are variable • Test piles are spaced widely apart • Getting this type of research going is a big effort • Requires the ‘right’ geotechnical conditions, too www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Driven—Large vs Small Diameter 14” CEP, No Epoxy 24” CEP, Epoxy www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Set-up—Large vs Small Diameter • Marquette Interchange, Wisconsin • 12.75, 14, 16 inch diameter at SLT site • Complications • Time after driving 16, 50 d • Mobilization 14 • Driving order (pore pressures) • Densification 16, 78d • Soil displacement 14 • Vibration • Signal match (CAPWAP) distribution precisions 12 www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Large vs Small Diameter • Scaling is not well understood • ADSC research project underway for drilled piles • Larger diameter piles likely take more displacement to fully mobilize • Can be a challenge with significant set up and inadequately sized hammer • Larger diameter piles more likely to also have lower velocities, different dynamic response • Statically, different displaced volumes of soil or plugging behavior www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Large vs Small Diameter • Experiences from other attendees www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Deep Foundation Testing, Multiple Topics • PDA/CAPWAP applied to large diameter piles versus small diameter piles • PDA/CAPWAP challenges for open ended piles • Thermal Integrity Profiling (TIP) • How to interpret CSL results for acceptance of shafts; when to remediate/repair/replace, etc. based on test results • Determining capacity and assessing integrity of a damaged pile or drilled shaft through dynamic testing • SPT Analyzer best methods for determining energy transfer of automatic hammers www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Challenge 1: Wave Speed • For many years, steel wave speeds constant • Past 10 years, PDI clients (GRL, Domestic, Property US International) noted apparently faster wave speeds on LDOEP • Timing of toe reflection was earlier than Wave Speed 16,800 ft/s expected • Different PDA units and models Unit Weight 492 lb/ft 3 • Pile Short? Damage? • For restrikes, tough to say! Elastic Modulus 30,000 ksi • Initial Drives from very first blow confirmed • Wave speeds were increasing by 2-3% www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Minnesota • 42 inch O.D. x 0.75 inch wall (1067 mm x 19 mm), open end pipe piles • ASTM A-252 Grade 3 steel, specified minimum F Y = 50 ksi • Piles were made from hot rolled black steel coil converted to spiral weld pipe • • 70 ft long top section welded to previously driven first section • Two PR accelerometers attached 7 ft from top • Two additional PE accelerometers attached 71.2 ft from top • Distance between PR and PE accelerometers of 64.2 feet www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Minnesota www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Challenge 1: Wave Speed • Dynamic test records on 30 to 48 inch diameter have supported the need for a 1 to 3% faster overall wave speed. • Not PDA unit dependent • Multiple Steel Grades, 45 ksi or more • Faster overall wave speed greater than 16,800 ft/s may be justified by early, easy driving records with carefully documented lengths • Should not be assumed without early data—might miss pile toe damage. • Faster overall wave speeds have NOT been observed on smaller diameter steel pipe piles (<24 inch) or hot rolled H-piles. www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Challenge 2: Constrictor Plates • Recent projects in the Midwest • Kentucky Lakes, Kentucky • Gnadenhutten, Ohio • Effect of constrictor plates on dynamic behavior • Modeling in CAPWAP www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Kentucky Lakes • Analysis complicated by constrictor plate, soil plug, pore water pressures • Use of radiation damping model • Modeling of soil plug • Resistance from constrictor plate included in shaft resistance total • Superposition of shaft resistance and end bearing used to evaluate resistance during restrike • Under prediction of static resistance possible due to failure mode under dynamic vs. static load www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Ohio www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Challenge 3: Internal Soil • Brown’s NCHRP Synthesis noted high accelerations on the plug may cause it to slip dynamically but not statically • Constrictor plate models indicated radiation damping may be a solution • Current internal research looks at numerical models www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
OUR PLUG MODEL We add at the bottom segment an interface force N-2 representing friction between inside pipe and plug N-1 N M plug 17 www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
OUR PLUG MODEL We add at the bottom segment an interface force representing friction between inside pipe and plug N-2 And a Plug End bearing in addition to the pile end N-1 bearing N M plug 18 www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Challenge 3: Internal Soil • Top Displacements • Plug End bearing: • 662 kips • Internal shaft resistance: 331/662/800/1200 kips www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Challenge 4: Comparison Data • Petek et al (forthcoming) ran database studies • Well documented case histories with dynamic, static and suitable geotechnical studies are hard to find • Alpha method correlated reasonably well with static load tests • Beta method was much more scattered • Dynamic tests, when available, were not well documented • Instrumented static load tests are difficult • Sensor survival when welded and protected www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
Deep Foundation Testing, Multiple Topics • PDA/CAPWAP applied to large diameter piles versus small diameter piles • PDA/CAPWAP challenges for open ended piles • Thermal Integrity Profiling (TIP) • How to interpret CSL results for acceptance of shafts; when to remediate/repair/replace, etc. based on test results • Determining capacity and assessing integrity of a damaged pile or drilled shaft through dynamic testing • SPT Analyzer best methods for determining energy transfer of automatic hammers www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
TAG – Cloud Thermal AGgregator • TAG doubles as TAP box for data collection • Wireless System aggregates information from TAP boxes to the TAG • Data sent to the Cloud via wireless modem • Data retrieved in office via internet connection (user password protected) www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com
350 Foundation Shafts (48 inch dia.) 6 – number completed when problem noted (groundwater washed out concrete for all 6 piles when casing was pulled) Construction technique was corrected 85 - number completed when CSL testing is normally made (7 days) 120 - number completed when report is normally issued (10 d) Center @ cage www.grlengineers.com | info@grlengineers.com 23
Recommended TIP Criteria S atisfactory (S) < 6% Radius Reduction and Cover Criteria Met Anomaly requiring further E valuation (E) Radius Reduction > 6% or Cover Criteria Not Met (a uniform 6% reduced radius is a 12% area reduction and a 22% bending capacity loss) minimum cover – 4 inch - AASHTO minimum cover – 3 inch - ACI Need larger design cover to allow for cage eccentricity so net cover is sufficient www.grlengineers.com | info@grlengineers.com
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