基于Pasternak地基模型的非线性土抗力-桩身侧向位移曲线在基坑支护桩中的应用

Application of nonlinear soil resistance-pile lateral displacement curve based on Pasternak foundation model in foundation pit retaining piles

支护桩作为基坑开挖过程中的直接挡土结构,在水平荷载作用下,桩身的内力与变形情况对基坑工程的安全性和经济性影响较大。为了更准确地计算支护桩的内力与变形,依据桩-土相互作用的非线性土抗力-桩身侧向位移(p-y)曲线,得到呈非线性变化的地基反力模量,同时引入Pasternak双参数地基模型充分考虑桩侧土体受力变形的连续性,推导了考虑桩-锚变形协调的支护桩挠曲微分方程,并利用传递矩阵法求得支护桩的内力与变形。结合工程实例编制计算程序,并将程序计算结果与监测值、基于传统Winkler地基模型的p-y曲线法计算结果对比分析,发现传统Winkler单参数地基模型会高估支护桩的水平变形和内力,而程序计算的位移和弯矩能更好地满足工程实际要求。进一步采用有限元软件对工程实例进行数值模拟分析,验证基于非线性Pasternak双参数地基模型的基坑支护桩计算方法的合理性和适用性。

As a direct retaining structure in the process of foundation pit excavation,the internal force and deformation of pile under horizontal load have great influence on the safety and economy of foundation pit engineering.In order to calculate the internal force and deformation of the supporting pile more accurately,the nonlinear foundation reaction modulus is obtained according to the nonlinear soil resistance-pile lateral displacement(p-y) curve of pile-soil interaction.At the same time,the Pasternak two-parameter foundation model is introduced to fully consider the continuity of pile side soil deformation.The differential equation of retaining pile deflection considering pile-anchor deformation coordination is derived,and the internal force and deformation of the retaining pile are obtained by the transfer matrix method.Then the calculation program is compiled based on the engineering example,and the calculation results of the program are compared with the monitoring values and the calculation results of the p-y curve method based on the traditional Winkler foundation model.It is found that the traditional Winkler foundation model will overestimate the horizontal deformation and internal force of the retaining pile.The displacement and bending moment calculated by the program can better meet the actual requirements of the project.Furthermore,the finite element software is used for numerical simulation analysis of the engineering example to verify the rationality and applicability of the calculation method of foundation pit supporting piles based on the nonlinear Pasternak two-parameter foundation model.