考虑基桩嵌岩段侧阻的岩溶区顶板安全厚度计算

为考虑岩溶区基桩嵌岩段侧阻力的影响,提出了一组确定岩溶区桩端顶板安全厚度的计算方法。考虑顶板的整体承载效应,结合弹性力学及第一强度理论,得到了顶板抗弯安全厚度计算式;考虑嵌岩段桩侧摩阻力对桩顶荷载的分担作用,结合格里菲斯判据及摩尔判据,获得了顶板抗冲切和剪切的安全厚度计算公式,进而运用ABAQUS建立了岩溶顶板与基桩整体分析计算模型,有限元计算结果与理论计算值吻合良好。结合工程实例重点分析了顶板厚跨比对抗弯安全厚度的影响,顶板岩层厚度对抗冲切、剪切安全厚度的影响以及嵌岩段侧摩阻力系数?对顶板安全厚度计算的影响。

Study on thickness of safety for cave roofs suffered bending failure in karst areas

Considering the impact of the shaft friction on rock-socketed section in karst area, a series of methods was developed to determine the safe thickness of cave roof. Firstly, considering the bending stiffness of the entire rock roof, the equation of anti-bending thickness can be acquired by using elastic theory and the first strength theory. Secondly, considering the contribution of the shaft friction for altering the distribution of the load on pile, the Griffith criterion and Mohr criterion were introduced to check computations of the anti-punch-shearing and the anti-shearing capacities of the cave roof respectively. Then, the accuracy and correction of the method verified by ABAQUS, and the integrated analyzing model for the cave roof and the rock-socketed pile is simulated. The calculated result agreed well with the simulation’s result. Finally, the effect of the ratio of roof thickness and span on the thickness of the safe roof were investigated, while the effect of the nature roof thickness on anti-punch-shearing and anti-shearing capacities and the effect of coefficient of rock-socketed friction on safe cave roof thickness were analyzed as well.