三轴条件下完整岩石Hoek-Brown强度准则的改进

Modified Hoek-Brown strength criterion for intact rocks under the condition of triaxial stress test

Hoek-Brown准则作为应用最广的岩石强度准则之一,其主要有2个方面的局限性:1)在常规三轴高围压条件下,根据Hoek-Brown准则预测的强度与试验实测的强度数据偏差较大;2)在真三轴条件下,该准则忽略了中间主应力对岩石真三轴强度的影响。为了克服以上局限性,引入Barton提出的临界围压和Singh中间主应力处理办法对Hoek-Brown准则进行改进。通过大量完整岩石强度试验数据分析改进的Hoek-Brown准则对三轴强度预测的适用性,分析结果表明:在围压低于临界围压时改进前后2个准则预测的岩石强度基本一致,而在围压高于临界围压时改进的Hoek-Brown准则预测的结果与试验数据更吻合;真三轴试验条件下,考虑中间主应力的改进的Hoek-Brown强度准则与试验结果的平均误差最小。因此,改进的Hoek-Brown强度准则更适用于完整岩石的三轴强度的预测。

As one of the most widely-used rock strength criteria, Hoek-Brown criterion mainly suffers two limitations. Firstly, the triaxial strength results predicted by Hoek-Brown criterion at high value of confining pressure do not agree well with experimental data. Secondly, the effect of intermediate principal stress to rock true triaxial strength is ignored by the criterion. In the present study, to overcome the limitations, Hoek-Brown strength criterion is modified by employing Barton＇s critical confining pressure and Singh＇s treatment of intermediate principal stress. The applicability of the modified criterion has been verified by its application to a large number of intact rocks experiment data. The analyzing result shows that the strength predicted by the two criteria are basically consistent when confining pressure is under critical confining pressure; otherwise the modified Hoek-Brown criterion agrees better with experimental data. Under the condition of true triaxial test, the average error between modified Hoek-Brown criterion considered intermediate principal stress and experimental data is the least. Thus,the modified Hoek-Brown criterion is more suitable to predict triaxial strength of intact rocks.