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圆孔作为一种典型的岩石缺陷,对岩石的力学特性具有重要影响。采用室内试验及PFC2D程序,构建含双圆孔类岩石试样并对其进行单轴压缩试验,研究其不同圆孔间距、倾角组合条件下的强度、裂纹模式及破裂孕育演化特征。研究表明:(1)当间距不变时,随倾角的增大,试样单轴抗压强度呈先减小后增大的趋势,且在倾角为45°~60°时达到最低单轴抗压强度;当倾角为90°恒定时,随间距的增大,试样单轴抗压强度呈先增大后减小的趋势,且在间距为40 mm左右时达到最大单轴抗压强度。(2)试样产生的裂纹类型可分为I型(张拉型)裂纹、II型(剪切型)裂纹、III型(混合型)裂纹等三类。当孔距较近时,随倾角的增大,圆孔间裂纹类型逐渐由III型裂纹转变为II型裂纹,两圆孔靠近加载端部一侧的孔壁逐渐产生I型裂纹,靠近试样两侧边界处的孔壁始终会产生II型裂纹。当倾角为90°恒定时,随间距的增大,两孔间相互作用减弱,但两圆孔靠近加载端部一侧及靠近试样两侧边界处的孔壁,始终分别产生I型裂纹和II型裂纹。(3)两孔间岩桥连线上的II型裂纹首先产生,其次在圆孔靠近加载端部一侧的孔壁产生I型裂纹,最后在圆孔靠近试样两侧边界处的孔壁产生II型裂纹。通常构成II型裂纹的声发射事件破裂强度,高于构成I型裂纹的声发射事件破裂强度。
As a typical rock defect, circular hole has an important influence on the mechanical properties of rock. The indoor test and PFC2D program were used to construct the double-hole rock specimen and to uniaxial compression test to study the strength, crack mode and rupture evolution characteristics under different combinations of pitch and pitch of circular hole. The results show that: (1) With constant pitch, the uniaxial compressive strength of the specimens decreases first and then increases with the increase of the inclination, and reaches the lowest uniaxial resistance at 45 ° ~ 60 ° When the inclination angle is constant at 90 °, the uniaxial compressive strength of the specimen first increases and then decreases with the increase of the spacing, and reaches the maximum uniaxial compressive strength at a spacing of about 40 mm. (2) The types of cracks produced by the specimens can be classified into three types: Type I (tension type), Type II (shear type), Type III (mixed type). When the hole distance is short, with the increase of the inclination angle, the type of cracks between circular holes gradually changes from type III to type II, and type I cracks are gradually produced near the hole wall on the side of the loading end, close to the sample Hole walls at both sides of the boundary always produce Type II cracks. When the inclination is 90 ° constant, with the increase of the spacing, the interaction between the two holes weakens. However, the two round holes near the loading end and the hole wall near the boundary of both sides of the specimen always produce I-type cracks and Type II crack. (3) Type II cracks on the rock bridge connection between the two holes are firstly generated, and secondly, type I cracks are generated in the hole wall on the side close to the loading end of the circular hole, and finally the hole wall near the boundary of the circular hole Type II cracks. The rupture strength of acoustic emission events that usually form type II cracks is higher than the rupture strength of acoustic emission events that form type I cracks.