一种新的软-硬节理峰值剪切强度模型

A new peak shear strength model for soft-hard joint

岩体中常存在强度不同的界面,其剪切强度影响岩体稳定,剪切强度的评估较为重要。利用3D技术打印的树脂节理板,浇注含不同粗糙度软-硬节理的不同强度水泥砂浆试样,在常法向应力下进行直剪试验和数值模拟研究,得到的剪切应力-位移的试验曲线与模拟曲线相一致。基于试验结果,引入比例系数T表征软-硬节理的组合壁面强度CCS,引入影响因子μ描述节理粗糙系数JRC、节理壁面强度JCS和法向应力σ_(n)对软-硬节理峰值剪切强度τ_(p)的综合影响效果,利用数值分析方法推导出一种估算软-硬节理峰值剪切强度的模型。试验发现:软-硬节理的残余剪切强度τr主要由JCS较低侧控制,且这种控制作用随JRC增大而增强;CCS值小的剪切应力-位移曲线率先达到峰值和进入残余阶段。研究表明:软-硬节理峰值剪切强度模型综合了JRC、JCS和σ_(n)对节理τ_(p)的影响机制,可用来评估粗糙软-硬节理的峰值剪切强度。

Interfaces with different strengths are usually existed in rock mass,the shear strength of these interfaces plays a critical role on the stability of rock mass,and it is thus highly important to accurately evaluate their shear strength.With the help of3 D-printed resin molds,the soft-hard jointed cement specimens with different joint roughness coefficients(JRC)and joint wall compressive strengths(JCS)were fabricated to conduct laboratory tests and numerical simulation of direct shear under constant normal stress.The test curves of shear stress-displacement agree with those by numerical simulation.Based on the test results,a coefficient of proportionality T was proposed to characterize combined compressive strength CCS of soft-hard joint,and meanwhile an influence factorμwas proposed to characterize the effects of JRC,JCS and normal stressσ_(n) on the peak shear strength of soft-hard joint by calculation and statistics method,thus a method for estimating the peak shear strength for soft-hard join surface was derived.The residual shear strength of soft-hard joint is mainly controlled by the soft joint side,and this control effect increases with the increase of JRC.The shear stress-displacement curves of soft-hard joint with smaller CCS earlier reach the peak and enter the residual stage.The study indicates that the proposed model may be used to evaluate the peak shear strength of soft-hard joint by integrating the influence mechanism of j oint surface morphology,joint compressive strength and normal stress.