按桩顶沉降量控制超长灌注桩竖向承载力研究

采用桩端阻三折线、桩侧阻双折线荷载传递模型,对基桩竖向承载力进行深入分析,提出了按桩顶沉降量控制大直径超长灌注桩基桩竖向承载力的设想,并导得了多层地基中桩周桩端土层处于各种不同状态下的竖向承载力解析解。该解答不仅能考虑桩周土的分层,还能考虑桩端土体的非线性及沉渣的影响。最后,采用本文方法对两根试桩的实测荷载-沉降曲线进行了比较分析,结果表明二者基本吻合,计算方法可供工程实践参考。

EVALUATION OF VERTICAL BEARING CAPACITY OF SUPER-LONG BORED SINGLE PILE BY THE PILE HEAD SETTLEMENT

The load transfer mechanism and bearing characteristics of super-long bored single pile are addressed in this paper. A tri-linear model and a bi-linear model are adopted for the toe and the shaft resistance, respectively. An analytical solution to predict the vertical bearing capacity is obtained, taking into account various bearing status of the soil or bedrock around the pile shaft and under the pile toe. The influence of different soil strata, nonlinear behavior of the surrounding soil or bedrock, and the sediment under the pile toe are considered as well in the present solution. An idea to predict or control the axial bearing capacity of large-diameter and super-long bored piles by the allowable pile head settlement is proposed herein. With the analytical method, good agreement between the predicted and measured load-settlement variations of a few test piles is reached, demonstrating the validity of the method in engineering practice.