Load Transfer Curves along Bored Piles Considering Modulus Degradation

The load-transfer (or t-z) curve, which reflects the interaction between a pile and the surrounding soil, is important for evaluating the load-settlement response of a pile subjected to an axial load using the load-transfer method. Preferably, the nonlinear stress-strain behavior of the soil should be incorporated into the t-z curve. This paper presents a practical approach for the estimation of t-z curves along bored piles by considering the nonlinear elastic properties and modulus degradation characteristics of the soil. A method for evaluating the modulus degradation curve from the results of a pressuremeter test is proposed. The results of load tests on one instrumented bored pile in Piedmont residual soil in Atlanta and another in the residual soil of the Jurong Formation in Singapore provide verification of the validity of the proposed approach.