砂-结构接触面直接剪切的物理试验与数值模拟

Physical experiment and numerical simulation of sand-structure interface's direct shear

利用DRS-1型超高压直残剪试验系统以及颗粒流软件PFC2D,对砂与地下结构的接触面分别进行了直接剪切物理试验与数值模拟,获得了砂与地下结构接触面力学特性的宏观表象及内在机理.结果表明:砂与地下结构接触面的剪切应力-剪切位移曲线随法向应力的增加,其应变软化特性逐渐减弱而硬化特性逐渐增强.在一定法向应力条件下,随着结构面粗糙程度的增加,应变软化特性增强,且达到峰值剪应力所需要的剪切位移逐渐减小;随着法向应力的增加,结构面粗糙度对接触面力学特性的影响程度降低.在一定的法向应力条件下,对同一结构面,接触面的剪切强度符合摩尔-库伦强度准则;不考虑颗粒破碎时,颗粒的"剪胀"是引起砂-结构接触面剪切强度变化的主要原因之一;当相对粗糙度R较小时,结构面的存在所引起的剪胀量较小,接触面的峰值剪应力较小;随着R增大,颗粒受结构面的约束,引起的剪胀量变大,峰值剪应力增加;当R增大到一定程度时,结构面对颗粒运动的约束作用所引起的试样剪胀量变小,峰值剪应力亦随之降低.

The physical experiment and numerical simulation of sand-structure interface direct shear were conducted by using DRS-1high normal stress residual shear apparatus and PFC2D（Particle Flow Code in 2Dimensions）software.The macroscopic representation and inherent mechanism of the mechanical properties of sand-structure interface were obtained.The results show that the strain softening weakens and strain hardening heightens as the roughness increasing under certain normal stress.At same time,the shear displacement corresponding to the peak shear stress reduces gradually.The influence of surface roughness reduces as normal stress increaseing.For the same structure,shear strength at the sand-structure interface meets Mohr-Coulomb criterion.In a certain normal stress conditions,soil particles shear dilation is one of the main reasons which cause the shear strength of the sand-structure interface to changewithout considering the particle breakage.When the relative roughness R（which is defined as the ratio of peak-valley distance to average particle size,R=H/d50）is smaller,soil particles shear dilation caused by interface constraint and the peak shear stress are all smaller.Both soil particles shear dilation caused by interface constraint and the peak shear stress increase as the relative roughness Rincreasing.When Rincreases to a certain degree,soil particles shear dilation caused by interface constraint becomes small.So the peak shear stress reduces too.