基于桩–岩结构面特性的嵌岩桩荷载传递分析

 嵌岩桩的荷载传递特性主要取决于混凝土–岩石界面的剪切特性。基于桩–岩结构面剪胀及破坏机制，建立适于弱质岩石嵌岩桩侧摩阻力传递模型，求得破坏及弹性条件下桩侧摩阻力及桩身轴力的解析式，并由此推导出嵌岩桩的临界长度。基于所获得的解答，深入探讨桩侧摩阻力和桩身轴力随深度变化的分布规律，从理论上分析嵌岩桩桩径、桩–岩模量比、剪胀角对嵌岩桩荷载传递的影响，并提出有关设计建议。提出可近似考虑各因素综合影响系数h，可作为嵌岩桩承载性能的宏观控制指标。同等条件下，h值越大，嵌岩桩承载性能越好，能承受的极限荷载也越大。工程算例对比分析结果表明，理论计算与实测结果吻合较好，对嵌岩桩设计有一定参考价值。

ANALYSIS OF LOAD TRANSFER OF ROCK-SOCKETED PILES BASED ON CHARACTERISTICS OF PILE-ROCK STRUCTURAL PLANE

The load transfer characteristics of rock-socketed pile are mainly decided by the shear behavior of rock-concrete interface. Based on the dilatancy and failure mechanisms of the interface between pile-rock and surrounding rock，a new load transfer function of skin friction suitable for the weak rock-socketed piles is set up；analytical solutions for the friction and axial force of single pile are obtained under the conditions of failure and elasticity of the surrounding rock；and the analytical solution of critical pile length is obtained as well. On the basis of those，the distributions of frictional resistance and axial force along the pile length are discussed，which can explain theoretically that the diameter of pile，pile-rock modulus ratio and dilatancy angle influence the load transfer characteristics of rock-socketed piles；and some useful suggestions for rock-socketed pile design are also proposed. Moreover，an influential parameter h，which is used as macro-control guideline of rock-socketed pile bearing performance，is introduced to consider the comprehensive influential effect of various factors approximately. From analysis，it is found that，under the same condition，the higher the value of h is，the better the rock-socketed pile bearing performance is，and the bigger the pile ultimate load can sustain. Comparative analysis result of an engineering example shows that the values calculated by the presented method agree well with the measured data.