卸载速率对卸载诱发页岩滑移行为影响的试验研究  

Influence of unloading rate on mechanical behaviors of shales during unloading-induced slip processes

作　　者：季浩奇 刘日成[1] 蔚立元[1] 李树忱 王晓琳 JI Haoqi;LIU Richeng;YU Liyuan;LI Shuchen;WANG Xiaolin(State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China)

机构地区：[1]中国矿业大学深部岩土力学与地下工程国家重点实验室,江苏徐州221116

出　　处：《岩石力学与工程学报》2023年第8期1959-1972,共14页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家重点研发计划项目(2020YFA0711800);国家自然科学基金资助项目(51979272,52179118)。

摘　　要：为研究卸载速率对卸载诱发页岩滑移行为的影响,利用MTS815岩石力学试验系统对接近临界应力状态下的含节理页岩进行恒轴压分级卸围压的诱发滑移试验,卸载速率分别为0.01,0.1,1和10 MPa/min。试验结果表明:(1)锯切节理面在滑移试验后表面的微凸体平均高度出现降低且粗糙度变大。随着卸载速率的增加,试样的表面粗糙度系数(JRC)分别上升了22.68%,44.82%,38.49%和49.89%。(2)试样滑移速度随着围压卸载速率的增加而增加,且在相同卸载速率下试样的准静态滑移平均速度比蠕变滑移平均速度大2个数量级。蠕变滑移平均速度分别为4.87×10^(-6),2.52×10^(-5),3.99×10^(-4)和3.29×10^(-3)mm/s,相应的准静态滑移平均速度分别为7.39×10-4,5.98×10^(-3),2.8×10^(-2)和1.2×10^(-1)mm/s。(3)试样在0.1 MPa/min卸载速率下发生滑移时的围压卸载量最小且摩擦强化效果最弱。在0.01 MPa/min卸载速率下试样的摩擦强度在长期的蠕变滑移中得到强化,在动态滑移中表现出摩擦弱化特征。试样在1和10 MPa/min的卸载速率下在较短时间内发生滑移,且试样在动态滑移中表现出摩擦强化特征。(4)根据试验结果分析卸载速率在0.1~1 MPa/min之间存在临界值,当试样在临界卸载速率下发生滑移时,围压卸载量最小,使得节理面上积聚的应变能较小,能量在滑移释放时主要作用于微凸体以突破互锁效应,因此滑移释放的能量最小且产生最小的剪切位移,这对岩体工程的安全保障具有重要意义。To investigate the effect of the unloading rate on the unloading-induced slip mechanism of shale,the slip start-up of jointed shales is triggered by stepwise-unloading confining pressure with constant axial stress using MTS815 loading system,wherein the unloading rates are 0.01,0.1,1 and 10 MPa/min respectively.The results show that:(1)The asperity altitude of the saw-cut joint decreases and the roughness increases due to slip deformation.With the increase of the unloading rate,the joint roughness coefficient(JRC)of saw-cut morphology increases by 22.68%,44.82%,38.49%and 49.89%,respectively.(2)The slip velocity increases with the elevation of the unloading rate,and the average velocity of quasi-static slip is two orders of magnitude higher than that of creep slip at the same unloading rate.The creep slip average velocities are 4.87×10^(-6),2.52×10^(-5),3.99×10^(-4)and 3.29×10^(-3)mm/s,respectively.The corresponding average quasi-static slip velocities are 7.39×10^(-4),5.98×10^(-3),2.8×10^(-2)and 1.2×10^(-1)mm/s,respectively.(3)The unloading amount of confining pressure is the smallest and the friction strengthening effect is the weakest under 0.1 MPa/min.Under 0.01 MPa/min,the friction strength of the sample is well enhanced in the long-term creep slip,and the friction strength is weakened in the dynamic slip.At the unloading rate of 1 and 10 MPa/min,the sample will slip in a short time,and the friction strength is enhanced in the dynamic slip.(4)There is a critical unloading rate between 0.1–1 MPa/min,and the unloading amount of confining pressure is the smallest when the sample slips at the critical unloading rate.It presents that the strain energy accumulated on the joint plane is smaller and the energy mainly acts on the micro-convexities to break the interlocking during the slip,so the energy released after the slip is the smallest and produces the minimum shear displacement,which is of great significance for the safety of rock mass engineering.

关 键 词：岩石力学 卸载诱发滑移 卸载速率 节理粗糙度 摩擦因数 

分 类 号：TU45[建筑科学—岩土工程]