考虑界面效应的砂土静力触探物质点法模拟

Cone Penetration Test Numerical Simulation with the Material Point Method Considering the Interfacial Effect

研究目的:静力触探试验广泛应用于工程领域,但室内及原位试验在探究土体内部应变演化机理方面具有一定的困难。相比之下,数值模拟更加高效节约,也更有利于探究土体内部应变演化机理。传统的有限单元法是常用的一种数值方法,但在计算大变形问题时会出现网格畸变问题,造成数值困难。基于上述背景,本文引入一种固体力学中的新型数值计算方法--物质点法,能有效避免网格畸变问题,非常适用于岩土大变形问题的分析研究。因此,本文采用物质点法针对静力触探试验开展三维数值模拟工作,探究锥体贯入过程中土体内部塑性变形区域的演化规律及锥头贯入阻力随深度的变化规律;分析砂土内摩擦角、锥体尺寸等因素的变化对贯入阻力的影响;分析静力触探锥体与土体接触面的界面效应,即不同的摩擦系数对锥头贯入阻力的影响。研究结论:(1)采用广义插值物质点法模拟静力触探试验是合理且可行的;(2)随着锥体的贯入,其周围土体将逐渐屈服,产生弹塑性变形并形成明显的破坏区域;随着贯入深度的增大,锥体贯入阻力先逐渐增大,再趋于稳定;(3)根据土体强度及锥体尺寸参数试验,锥头最大贯入阻力随砂土内摩擦角的增大而增大,随锥尖角的增大而增大,随截面面积的增大而减小;(4)锥-土摩擦系数对于贯入阻力的大小具有显著影响,随着摩擦系数的逐渐增大,最大贯入阻力逐渐增大,两者近似呈线性规律;(5)本研究成果主要应用于静力触探试验机理的分析研究工作。

Research purposes: Static cone penetration test is widely used in engineering field. However,indoor and in-situ tests have some difficulties in exploring the internal strain evolution mechanism of soil. Compared with them,numerical simulation has the advantages of high efficiency and economy,being more conducive to exploring the internal strain evolution mechanism of soil. The traditional finite element method is a commonly used numerical method.However, when calculating large deformation problems, mesh distortion will occur, which results in numerical difficulties. Based on the above background,a new numerical method in solid mechanics,Material Point Method,is introduced. This method effectively avoids the mesh distortion problem,which is very suitable for the analysis of large deformation of rock and soil. Therefore,in this paper,three-dimensional numerical simulation of cone penetration test is carried out by using material point method,to explore the evolution law of plastic deformation zone and the variation law of cone penetration resistance with depth in the process of cone penetration. The influence factors such as internal friction angle of sand and cone size on penetration resistance is analyzed. The interface effect between the cone and soil,which also called friction coefficient,is analyzed to explore the influence to the penetration resistance.Research conclusions:( 1) It is reasonable and feasible to simulate static penetration test by generalized interpolation material point method.( 2) With the penetration of the cone,the soil around the cone will yield gradually,resulting in elastic-plastic deformation and obvious damage area. In addition, with the penetration depth increasing, the penetration resistance of the cone increases gradually at first and then tends to be stable.( 3) According to the parameter test,the maximum penetration resistance of the cone head increases with the increase of the friction angle in sand.( 4) The friction coefficient of the cone and soil has a significant influence on the penetration resistance,and the maximum penetration resistance increases with the increase of the friction coefficient,which is approximately linear.( 5) The research results are mainly applied to the analysis and research of static penetration test mechanism.