上覆土嵌岩扩底桩抗拔承载特性离心模型试验及计算方法研究

Centrifugal model tests and calculation method of uplift bearing capacity of rock-socketed pedestal pile overburden soil

随着我国西部输电线路工程的快速发展,杆塔基础抗拔问题日益突出,岩体的破坏模式、极限抗拔承载力的计算方法都是目前亟待解决的关键问题。根据离心模型试验结果,分析了岩体破坏模式、荷载-位移曲线、桩身轴力分布和桩侧摩阻力曲线。基于试验结果对岩体破坏形状进行无量纲化处理并拟合,得到了统一的函数描述形式。在此基础上,利用极限平衡法推导出上覆土嵌岩扩底桩极限抗拔承载力的计算方法,并对该计算方法作了简化分析,将积分计算值和简化计算值分别与离心模型试验结果进行对比。研究结果表明:上覆土嵌岩扩底桩的软质岩破坏模式为喇叭型曲面,可用统一的幂函数形式进行描述。简化计算方法的结果与离心模型试验结果吻合良好,提出的新方法对西部山区杆塔基础的抗拔设计具有参考和应用价值。

With the rapid development of the transmission line project in western China, the problems of the tower foundation uplift become prominent. It is necessary to solve the failure model of rock and the calculation method of ultimate uplift bearing capacity urgently. The centrifuge model test results are used to analyze the failure model of rock, load-displacement curve, axial force distribution and friction resistance curve of piles. According to the test results, after the failure shape of rock is non-dimensionally processed and fitted, a unified function description form is obtained. On this basis, the limit equilibrium method is used to derive the calculation method of ultimate uplift bearing capacity of the rock-socketed pedestal pile overburden soil, and the calculation method is simplified. The integral calculation value and the simplified calculation value are compared with the results of the centrifugal model test. The results show that the failure model of the soft rock is trumpet-shaped surface, which can be described by a unified power function. The results of the simplified calculation method are in good agreement with the results of the centrifugal model test. Therefore, the method proposed in this paper provides a reference for the uplift design of tower foundation in the western mountainous area.