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16 (CSL), 7% used Surface Reflection (Pulse Echo Method), TABLE 3 Driven piles database: soil and 7% used Gamma Ray or NX coring. type and number of cases by type of pile Soil Type Number of Cases Tip Side H-PILES PPC PIPE 2.2 DATABASES Clay 3 0 0 Sand 12 0 0 Rock Mix 6 15 3 2.2.1 General Total 21 15 3 Clay 0 0 0 Three major databases were developed for the primary sta- Sand 17 37 20 Sand tistical evaluation of resistance factors for the design and Mix 13 50 19 construction of driven piles and drilled shafts. Six additional Total 30 87 39 Clay 8 19 20 peripheral databases were assembled and/or used for the Sand 1 1 0 Clay investigation of specific issues as needed. The major features Mix 36 34 15 of the databases are described below. The detailed cases from Total 44 54 35 Insufficient data 0 7 1 which the databases were developed are presented in Appen- All cases (338) 97 163 78 dix B (dynamic) and Appendix C (static). 2.2.2 Drilled Shaft Database--Static Analysis and dynamically monitored during driving and/or restrike (403 analyzed measurements). PD/LT2000 comprises information The soil type and method of construction of the 256 case from the PD/LT database (Paikowsky et al., 1994), the PD/LT2 histories in the drilled shaft database are detailed in Table 2. database (Paikowsky and LaBelle, 1994), and 57 additional The database was developed at the University of Florida, pile case histories described by Paikowsky and Stenersen mostly through the integration of databases gathered by the (2000). The data in PD/LT2000 were carefully examined and Florida DOT, the Federal Highway Administration (FHWA), analyzed following procedures described by Paikowsky et al. and O'Neill et al. (1996). (1994), resulting in detailed static and dynamic pile capacity evaluations. Table 4 presents a summary of the data contained in PD/LT2000, broken down according to pile type and capac- 2.2.3 Driven Pile Database--Static Analysis ity range, site location, soil type, factors affecting soil inertia, and time of driving (EOD or BOR). The soil and pile type of the 338 case histories in the driven pile database are detailed in Table 3. The database was developed at the University of Florida, mostly through 2.3 DEEP FOUNDATIONS the integration of databases gathered by the University of NOMINAL STRENGTH Florida, the FHWA (see, e.g., DiMillio, 1999), the University of Massachusetts Lowell (see, e.g., Paikowsky et al., 1994), 2.3.1 Overview and the Louisiana Transportation Research Center. Probabilistic calibration of resistance factors for any pre- dictive method utilizing a database is possible when the nom- 2.2.4 Driven Pile Database--Dynamic Analysis inal geotechnical pile strength (i.e., static pile capacity) is defined and compared to the outcome of the calibrated pre- The PD/LT2000 database contains information related to diction method. The definition of ultimate static capacity given 210 driven piles that have been statically load tested to failure static load test results (load-displacement relations) is not unique, and the use of the term "reference static capacity for calibration" (may include judgment) is more appropriate than TABLE 2 Summary and breakdown--drilled shafts "nominal strength." The static load test results depend on the database load testing procedures and the applied interpretation method, Method of Construction often being subjective. The following sections examine each Soil/Rock Type Casing Slurry Dry Total Skin Total Skin Total Skin of these factors and its influence on the reference static capac- Sand 13 6 15 4 6 1 ity, concluding with a recommended unique procedure to be Clay 14 3 0 0 40 10 followed in the calibration. Mixed Soils 23 4 12 5 13 7 Rock 0 0 0 0 8 0 Sand & Rock 4 4 7 5 20 0 2.3.2 Failure Criterion for Statically Loaded Clay & Rock 2 0 2 0 19 7 Driven Piles Mixed Soils 2 1 0 0 2 0 & Rock Total (256) 58 32 36 14 91 25 Past work related to driven piles (Paikowsky et al., 1994) Note: Total = skin + tip; Skin = side alone has resorted to a representative static pile capacity based on
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17 TABLE 4 The PD/LT2000 database: pile type, geographical location, soil type, soil inertia, type of data, and pile capacities Geographical Pile Types Soil Types Soil Inertia Type of Data Pile Capacities Location Soil Blow Range Pile Type No. Location No. Side Tip Criteria AR Time No. No. Type Ct. (kN) Northeast H Pile 37 44 EOD 0-445 2 USA 16 & 92 Southeast BOR OEP 10 69 blows 272 ---- 445-890 6 USA Clay 67 61 /10cm North /Till CEP 61 24 EOD 890-1334 17 USA & 30 Voided South BORs 35 10 1334-1779 44 Concrete USA < 16 Northwest 254 9 3 blows 112 ---- 1779-2224 27 USA /10cm EOD 135 Southwest 305 5 14 2224-2669 25 USA Rock 0 11 356 8 Australia 2 2669-3114 15 New BOR 239 Sq. 406 1 Brunswick 3 350 ----- 134 3114-3559 10 Conc 457 8 Holland 4 3559-4003 13 EOR 11 Hong 508 8 4 4003-4448 13 Kong Sand 137 140 /Silt 610 16 Israel 4 < 350 ----- 255 4448-4893 11 DD 2 762 5 Ontario 22 4893-5338 6 Octagonal Sweden 1 5338-5783 5 3 DR 1 Concrete NA 3 1 NA 5 ---- 5783-6228 4 NA 6 Timber 2 ALT 1 6228-6672 6 Monotube 2 >6672 6 Total 210 210 210 210 389 389 389 210 Notes: Pile types: OEP = Open Ended Pipe Pile; CEP=Closed Ended Pipe Pile. Geographic Location: Northeast USA = Federal Highway Regions 1, 2 & 3; Southeast USA = Federal Highway Region 4; North USA = Federal Highway Regions 5, 7 & 8; South USA = Federal Highway Region 6; Northwest USA = Federal Highway Region 10; Southwest USA = Federal Highway Region 9. Type of Data: EOD = End of Driving; BOR = Beginning of Restrike; EOD & BOR = Cases containing both EOD & BOR; EOD & BOR's = Cases containing both EOD & multiple BOR measurements; EOR = End of Restrike; DD = During Driving; DR = During Restrike; ALT = Alternate measurement. NA = Non Applicable / unknown the assessment by five interpretation methods; (1) Davisson's was then determined. Details of the analyses and their results Criterion (Davisson, 1972), (2) Shape of Curve (similar to are presented by Paikowsky and Stenerson in Appendix B. the procedure proposed by Butler and Hoy, 1977), (3) Lim- Figure 6 shows the histogram and calculated distributions iting Total Settlement to 25.4 mm, (4) Limiting Total Settle- (normal and lognormal) for Davisson's failure criterion in ment to 0.1B (Terzaghi, 1942), and (5) the DeBeer log-log which KSD is the ratio of the designated static capacity to that method (DeBeer, 1970). defined by Davisson's failure criterion. Davisson's criterion A single representative capacity value was then calculated was found to perform the best overall and was therefore cho- for the analyzed case as the average of the methods consid- sen as the single method to be used when analyzing load- ered relevant (i.e., provided reasonable value). The develop- displacement curves. Davisson's method provides an objec- ment of a calibration in a framework suitable for future mod- tive failure criterion and was also found to perform well for ifications requires that the evaluated resistance factors be piles exceeding a diameter of 610 mm (examined through based on an objective, reproducible procedure. In order to do 30 pile cases). The data presented in Figure 6 demonstrates, so, the static capacity of each pile in database PD/LT2000 was however, that (1) a small bias exists in the static capacity evaluated according to all five aforementioned criteria and a being used as a reference for the evaluation of the methods representative capacity was assigned for each pile. The mean predicting the capacity of driven piles, and (2) this bias (and and standard deviations of the ratio of the representative pile other considerations) needs to be accounted for when evalu- capacity to the capacity given by the method being evaluated ating the resistance factor to be used for field static load tests.