Cover Image

Not for Sale

View/Hide Left Panel
Click for next page ( 20

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 19
19 weight dynamic testing. Another National Cooperative High- on their use. The associated correlations used to evaluate the way Research Program project, NCHRP-21-08 "Innovative soil properties from SPT and CPT tests are presented in Tables Load Testing Systems," headed by the principal author of 7a and 8, respectively. While two internal friction angle inter- this report, examines such alternative methods. As part of pretations are listed in Table 7 and were used initially, only this ongoing project, the static load-test results of statically the method proposed by Peck Hansen and Thornburn was loaded drilled shafts were examined utilizing the failure cri- found to provide more realistic results, and hence utilized in teria previously described for driven piles, and the FHWA the calibrated analyses. The methods and the correlations criterion for drilled shafts (O'Neill and Reese, 1999). The listed in Tables 7a and 8 are based on the state of practice FHWA criterion establishes the failure load as that associ- established via the questionnaire (see section 2.1 and Appen- ated with a displacement of 5% of the diameter at the shaft, dix A.) Table 7b elucidates the combinations and the manner if plunging of the shaft cannot be achieved. The results of in which the correlations were applied. The notations used this preliminary study, presented in Table 5, suggest that in Table 7b are further noted when the analysis results are the FHWA criterion provides a reliable and simple failure reported. The tables were, by and large, prepared as part of interpretation. For the presented LRFD calibration study, the the study of static pile capacity at the University of Florida, FHWA failure criterion for drilled shaft (i.e., load at a dis- which is presented in Appendix C. placement of 0.05 B) was, therefore, adopted. 2.5 DRIVEN PILES--DYNAMIC ANALYSIS 2.4 DRIVEN PILES--STATIC ANALYSIS METHODS METHODS 2.5.1 Overview Table 6 presents a summary of the methods used for static capacity evaluation of driven piles detailing the equations for Prior to detailed analyses leading to the determination of side and tip resistances, required parameters, and constraints resistance factors, two components must be established: (1) the TABLE 5 Evaluation of failure criteria for statically loaded drilled shafts Statistics for the Ratio between Drilled Shaft Capacity of Different Interpretation Methods and the Representative Capacity Davisson DeBeer Shape of Curve FHWA # mx x # mx x # mx x # mx x 47 0.862 0.17 39 0.908 0.11 36 0.956 0.09 40 0.999 0.13 Notes: # = no. of cases; mx = mean; x=standard deviation; loads 0.85 to 20 MN; diameter 0.3 to 1.5m; length 5.3 to 58.5m TABLE 6 Summary of static capacity methods for driven piles Method Side resistance Tip resistance Parameters Constraints required Su; +Bearing layer must be stiff -Tomlinson Db (bearing cohesive (Tomlinson, 1980/1995) qs = Su embedment) + Number of soil layers 2 -API (Reese et al., Su 1998) qp = 9 Su in cohesive (AASHTO, qs = ' OCR 1996/2000) (US Army Corps of qs = ('+2Su) Su Only for cohesive soils Engineers, 1992) in cohesionless ' Dr (Bowles, 1996) Nordlund and Thurman sin( + ) qp = q s = K C F' (Hannigan et al., 1995) cos t N'q ' Meyerhof SPT (Meyer- qp = + For cohesionless soils qs = k N N hof, 1976/1981) 0.4D/BN' + SPT data Schmertmann SPT (Lai qs = function(N) qp = fn(N) N SPTdata and Graham, 1995) Schmertmann CPT (McVay and Townsend, qs = function(fs) qp = fn(qc) qc, fs CPT data 1989)