石灰岩裂隙摩擦强度愈合的压力溶解和应力腐蚀模型研究

Model study of frictional healing of limestone fracture: The role of pressure solution and stress corrosion

为模拟试验中观察到的石灰岩裂隙摩擦强度愈合现象,提出用压力溶解和应力腐蚀相结合的综合模型来模拟裂隙摩擦强度的愈合。综合模型可同时考虑压力溶解和应力腐蚀对裂隙接触面的改造作用,通过裂隙接触面积的变化表征摩擦强度的愈合。模拟结果表明:压力溶解模型低估了短控制时间内摩擦强度的愈合量,通过进一步的参数敏感性分析发现,随着控制时间的增长,温度的升高显著地提高了压力溶解模型的模拟值,而有效应力的增加对模拟值的影响相对较小;应力腐蚀模型则主要反映应力压缩引起的裂隙接触面积增长;压力溶解模型和应力腐蚀模型结合则能较好地模拟裂隙摩擦强度的愈合。因此,用压力溶解模型模拟裂隙摩擦强度愈合时,特别是在模拟短控制时间内和低温条件下力学占主导作用的愈合时,应考虑应力腐蚀引起的裂隙接触面积变化。

A coupled model including the combination of pressure solution model and stress corrosion model is proposed to simulate the observed strength recovery of limestone fracture. Thus, the coupled model can consider both pressure solution and stress corrosion in modification of the fracture contact area, which is used to predict the frictional healing of the fracture. The simulation results show that the pressure solution model underestimates frictional healing during short hold times, and with extending the hold times, the simulated results of the pressure solution model obviously increase with the growth of temperature, whereas the results are slightly influenced by the effective confining stress. Generally, the stress corrosion model reflects the growth of fracture contact area caused by compaction. Therefore, the coupled model can simulate the frictional healing well observed from Slide-Hold-Slide（SHS） tests. In conclusion, the stress corrosion model should be considered, when the pressure solution model is employed to simulate the frictional healing, especially under short hold times and at low temperatures when the domain effects are mechanical.