Load transfer for piles in sand and the critical depth

Abstract

The authors analyzed the results from a static loading test on a 11.0-m, intrumented, precast concrete pile and presented the findings in two earlier papers. The findings are here extrapolated to verify the dependability of applying the results and analysis methods to predict the detailed behavior of a similar test pile driven 5 m away from the first pile and to a 4.0 m deeper embedment. This paper offers conclusions drawn from the analyses of both piles with regard to residual load and resistance distribution. A primary result of the analyses is the indication that the critical-depth concept is not valid. For full-length piles, the critical-depth concept originates because of neglects in analysis of test data, such as omission of the residual load and testing-sequence history. For tests on short piles and laboratory studies of model piles, a critical depth appears as a result of neglect of the influence of shallow-depth variation of the earth pressure coefficient. Key words : instrumented piles, sand, loading test, residual load, load transfer, finite element, constitutive modelling, critical-depth concept.