基于桩土界面摩擦特性和桩周土体应力状态的基桩极限侧阻力分析

Analysis of ultimate shaft resistance of foundation pile based on frictioncharacteristic of pile-soil interface and stress state of soil around pile

摘要:

结合基桩承载过程中的桩周土体应力状态分析和桩土界面摩擦特性分析，推导出基于土体应力状态的沿桩土界面的土体抗剪强度计算模型和基于界面摩擦特性的界面抗剪强度计算模型。通过对比土体抗剪强度和界面抗剪强度，推导出受该两种强度耦合作用影响的极限侧阻力计算模型，并用上海某工程算例验证该模型的合理性和可行性，同时利用该模型分析不同类型的土的极限侧阻力随埋深的分布规律。结果显示：因内摩擦角和侧压力系数之间的不同关系，极限侧阻力随埋深表现出不同的分布特点，在特定关系下，存在一个临界深度，超过该深度极限侧阻力维持在一个稳定值甚至不断减小直至为零。

关键词:应力状态;桩土界面;摩擦特性;极限侧阻力;临界深度

Abstract:

By analyzing the stress state of soil around a pile and friction characteristic of the pile-soil interface during the load bearing process of the pile foundation, a calculation model of shear strength of soil based on stress state of soil and calculation model of shear strength of interface based on friction characteristic of pile-soil interface is derived. By comparing the shear strength of soil with that of the interface, the calculating model of ultimate shaft resistance under the influence of the coupling of the two kinds of strength is derived, and the rationality and feasibility of the model is verified by an engineering example in Shanghai, and the distribution law of ultimate shaft resistance of different types of soil with buried depth is analyzed by using the model. The results show that, due to the different relations between the internal friction angle and the lateral pressure coefficient, the ultimate shaft resistance shows different distribution characteristics with buried depth, and in a certain relationship, there is a critical depth beyond which the ultimate shaft resistance is maintained at a stable value or even reduced constantly to zero.

Key words:stress state; pile-soil interface; friction characteristic; ultimate shaft resistance; critical depth