基于桩侧阻力强化效应的嵌岩桩承载力计算

CALCULATION OF BEARING CAPACITY OF ROCK-SOCKETED PILE BASED ON ENHANCED EFFECT OF SKIN FRICTION

根据常法向刚度条件下结构面剪切力学特性研究嵌岩桩的荷载传递机制。考虑桩–岩界面胶结作用,提出完整的嵌岩桩桩–岩界面剪切机制,即包括胶结破坏、滑动剪胀及剪切滑移3部分;根据桩–岩界面不同剪切阶段的力学特性,建立完整的桩–岩界面剪切本构方程。基于结构面剪切力学特性,从理论上分析嵌岩桩桩侧阻力强化效应的产生机制。研究结果表明,桩侧阻力增强效应在整个桩侧都有发生,但在桩端附近桩侧最为明显。在机制分析的基础上,提出考虑桩侧阻力强化效应的嵌岩桩竖向承载力理论计算方法,该法计算模式明显有别于传统桩基规范算法。工程算例对比分析结果表明,该方法计算值比桩基规范传统算法计算值更接近于现场实测静载试验结果。这一算法可为嵌岩桩设计与应用提供新的思路。

Based on the shear mechanical properties of structural plane under condition of constant normal stiffness, the load transfer mechanism of rock-socketed pile was studied. Considering the bond strength of pile-rock interface, a complete shear mechanism of pile-rock interface of rock-socketed pile was proposed, including bond damage, sliding dilatancy and shear slipping. According to the mechanical properties of pile-rock interface in different shear stages, complete shear constitutive equations for pile-rock interface were put forward. On the basis of shear mechanical properties of pile-rock interface, the enhanced effect of skin friction was analyzed theoretically. The results show that the enhanced effect occurs at the whole pile side and is the most distinct in the vicinity of pile tip. Considering the enhanced effect of skin friction, the theoretical formula for vertical bearing capacity of rock-socketed pile was proposed, which is obviously different from the traditional method suggested by specifications. Comparative analysis of case study shows that the vertical bearing capacity calculated by the proposed method is much closer to the field static load test result than the value calculated by the specifications. It provides a new procedure for design and application of rock-socketed piles.