考虑三向应力的弱面岩石强度分析

Analysis of rock strength with weak planes concerning tri-axial stress

弱面岩石通常具有明显的强度各向异性,一般的弱面理论都是在平面应力状态内分析岩石强度,不能准确分析所有的弱面情况。借助张量的坐标转换方法,计算空间任意方位上的弱面应力分量,建立考虑三向应力的弱面岩石剪切强度模型。分析结果表明,对于单弱面岩石,中间主应力对岩石强度的影响是非常大的。当(中间主应力)σ_2≠σ_3(最小主应力)时,弱面岩石的强度受剪切破裂面法向与最大主应力之间的夹角β和弱面倾向α同时控制,岩石强度随b的变化规律与传统模型预测的规律相差较大。α较大的情况下岩石表观强度通常会比较高。α较小的情况下,σ_2较小时岩石表观强度变大,σ_2较大时岩石表观强度变小。使用考虑三向应力的强度模型可以精确预测弱面在任意一角度时的岩石强度。

The shales strength properties of anisotropic is significantly for it＇s weak planes.Strength analysis of weak plane rocks usually uses the single plane of weakness theory of Jeager J.C.However,this theory is limited for that didn＇t calculate the intermediate principal stress.This paper utilizes a method of calculating the stress in weak plane by tensor transformation rule.The analysis indicates that the shear strength model of weak plane rocks under tri-axial stress,because of single plane of weakness,the intermediate principal stress has a great influence on strength.While σ2≠σ3,the strength of weak plane rocks is determined by β and α.The laws of strength changing with β are different from conventional models＇.With the increase of σ2,the danger region of weak plane normal changes from symmetrical around the σ1 to symmetrical around the σ3.The new weak plane rock strength models provide accurate prediction for weak plane in any angle.