考虑法向应力与岩石强度的加锚节理岩体剪切力学模型研究

Research on shear mechanics model of anchored-jointed rock mass considering normal stress and rock strength

为分析法向应力和岩石强度对锚杆锚固效应的影响规律,选取红砂岩、石灰岩、玄武岩3种代表性岩石开展加锚节理岩体直接剪切试验,基于试验结果,根据静定梁理论和最小余能原理,建立考虑岩石结构效应和等效剪切面积的加锚节理岩体力学分析模型,并结合理论计算公式,分析不同锚固角下岩石强度对锚杆轴向力和剪切力的影响规律。研究表明:锚杆的锚固效应在宏观上表现为增加节理面的当量内摩擦角和黏聚力,且岩石强度越大,锚杆对节理面剪切强度的贡献值就越大。与试验数据和已有分析模型对比分析表明,理论模型的计算值与试验结果更为吻合。通过计算分析可知,随着锚固角的增加,锚杆轴向力对节理面剪切强度的贡献度逐渐减小,剪切力对节理面剪切强度的贡献度逐渐增加,并且锚杆最佳锚固角在50°~70°范围。

In order to analyze the influence of normal stress and rock strength on anchor bolt anchoring mechanism,three representative rocks,namely red sandstone,limestone and basalt,were selected to carry out direct shear tests of jointed rock mass under different normal stress levels.Based on the test results,according to the statically determinate beam theory and the principle of minimum complementary energy,this paper establishes a shear strength model of joint surface which considers the effect of rock structure and equivalent shear area.And combined with the theoretical calculation formula,this paper analyzes the influence law of rock strength on the axial force and shear force under different anchorage angles.The research shows the anchoring effect of anchor bolts is shown as increasing the equivalent internal friction angle and cohesion of joint surface,and that the greater the rock strength,the greater the contribution of the bolt to the shear strength of the joint plane.Compared with the experimental data and the existing analytical model,the calculated values of the theoretical model are more consistent with the experimental results.Through calculation and analysis,it can be seen that with the increase of the anchorage angle,the contribution of the axial force of the bolt to the shear strength of the joint surface gradually decreases,while the contribution of the shear force to the shear strength of the joint surface gradually increases,and the optimal anchorage angle of the bolt is within the range of 50°to 70°.