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UBC Theses and Dissertations

Prediction of pile drivability from CPT and WEAP analysis Wang, Jaiwei


Pile drivability is a difficult problem because of the complex dynamic pile-soil behaviour. The current procedure in predicting blow count during pile driving uses the Smith’s one-dimensional wave equation model with input appropriate soil resistances during pile driving. There is no general consensus to date on one approach for estimating the driving resistances in all types of soils. The cone penetration test (C PT) is a useful tool for detailed profiling of soil conditions at a site and has been found by many researchers to provide a reliable estimate of long term pile capacity as determined from a static loading test. An attempt has been made in this thesis to use the CPT directly to estimate pile driving resistance for use in pile drivability analysis. Several approaches were undertaken to estimate the driving resistances from the CPT, and the predicted blow counts from the wave equation analysis were compared to the field measured blow counts. Pile and soil data from three sites: UBC Pile Research Site, Tilbury Island Site and Evanston Campus of Northwestern University (ENCU) Site were analyzed. The piles included steel pipe piles of both closed and open ended as well as H pile. An empirical correlation approach is proposed which uses CPT cone bearing (qc) directly to estimate the driving toe resistances. The shaft resistances during driving, however, was estimated in a conventional way from static long term resistance calculated from correlations with CPT q,, data but was then multiplied by a set of empirical de termined reduction factors. The application of the proposed method to a steel pipe pile at another site location (not included in the above data base) is illustrated. Reasonable agreement is obtained between calculated and measured blow counts. Although the data base in this study is limited, the proposed method appears promis ing. More research is needed to check the applicability of this method to different soil condition and other pile types.

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