Ⅱ型加载条件下页岩断裂行为的预测研究  

Prediction of shale fracture behavior undermodeⅡloading

作　　者：杨秀锟 谢秦 刘希灵[1] 李生相 曾媛 YANG Xiukun;XIE Qin;LIU Xiling;LI shengxiang;ZENG Yuan(School of Resources and Safety Engineering,Central South University,Changsha 410083,Hunan,China)

机构地区：[1]中南大学资源与安全工程学院,湖南长沙410083

出　　处：《实验力学》2023年第1期109-118,共10页Journal of Experimental Mechanics

基　　金：国家自然科学基金(42172316);湖南省自然科学基金(2021JJ30810)资助。

摘　　要：实际工程中岩体往往处于Ⅰ型和Ⅱ型加载同时存在的状态,而这种复合加载条件下岩石断裂行为的预测较为复杂,也是迫切需要解决的问题。本文基于Ⅰ型加载条件下测试得到的页岩试样断裂韧度,应用MTS(Maximum Tangential Stress,最大切向应力)断裂准则对页岩试样在Ⅱ型加载条件下的裂纹起裂角以及断裂韧度进行了预测。为评估预测效果,通过Ⅱ型加载条件下2种尺寸页岩断裂试验,发现Ⅰ型断裂韧度随岩样尺寸变化的趋势不同,Ⅱ型断裂韧度基本没有尺寸效应。通过比较预测结果以及试验结果发现,利用传统的MTS断裂准则预测的理论值与试验测试值相差较大。在预测过程中断裂过程区尺寸的确定也是非常重要的,如果不考虑断裂过程区的尺寸效应同样会造成很大的预测误差。结合MTS准则确定的断裂过程区尺寸,利用GMTS(Generalized Maximum Tangential Stress,广义最大切向应力)断裂准则预测的岩样裂纹起裂角以及断裂韧度都与试验测试值非常接近。Rock mass is usually under modeⅠandⅡloading conditions in practical engineering,but the prediction of rock fracture behavior under mixed modeⅠ/Ⅱloading condition is complicated,and it is an important problem to be solved.Based on the fracture toughness of shale specimens tested under modeⅠloading condition,the MTS(maximum tensile stress)criterion was applied to predict the crack initiation angleand fracture toughness of shale specimens under modeⅡloading condition.In order to evaluate the prediction effect,the fracture tests on shale of two sizes under modeⅡloading was carried out,it is find that different from the variation trend of mode I fracture toughness with rock specimen size,modeⅡfracture toughness basically has no size effect.By comparing the predicted results with the test results,it is found that the predicted values of the MTS criterion differ greatly from the test results.The size of the fracture process zone is also a very important parameter in the prediction process.Failure to consider the size effect of the fracture process zone likely to cause great prediction errors.Based on the size of fracture process zone determined by the MTS criterion,the failure loadand the crack initiation angle predicted by the GMTS(generalized maximum tangential stress)criterion are very close to the test values.

关 键 词：页岩 断裂韧度 最大切向应力断裂准则 断裂过程区 

分 类 号：TU452[建筑科学—岩土工程]