裂隙数量和开度对低强度岩体力学特性及破坏模式的影响

采用MTS815电液伺服控制试验机对不同裂隙数量和不同裂隙开度条件下的低强度岩体试件进行常规单轴压缩试验，基于试验结果，详细分析了每种类型裂隙试件的应力-应变曲线、强度、变形参数及破坏模式。研究结果表明:① 裂隙数量可使试件应力-应变曲线的峰后破坏阶段由快速下跌转变为台阶式下跌，最后变为水平延伸式缓慢下跌，呈近似塑性流动变形破坏，相对而言裂隙开度对试件应力-应变曲线的影响则非常小;② 受结构效应的影响，试件峰值强度只在水平和倾斜裂隙条件下才随裂隙数量的增加呈明显减小趋势，而裂隙开度对试件峰值强度的影响较小，且存在最弱影响开度值;③ 裂隙数量对不同裂隙倾角条件下试件的变形特征均有较大影响，而裂隙开度只对倾斜裂隙试件的变形特征影响较为明显;④ 裂隙数量对倾斜和垂直裂隙试件破坏模式的影响要比水平裂隙试件的明显，但影响规律不明确。裂隙开度可以完全改变垂直裂隙试件的破坏模式，使其由纯拉伸破坏向单一剪切破坏转变，但对水平和倾斜裂隙试件的破坏模式基本没有什么影响。

Effect of fracture number and aperture on mechanical properties and failure modes of low-strength rock mass

Conventional uniaxial compression test on low-strength fractured specimens with different fracture numbers and fracture apertures are carried out by using the MTS815 electro-hydraulic servo control test machine.The stress-strain curves,strength,deformation parameters and failure modes of various types of low-strength fractured specimens are analyzed based on the experimental results.The main conclusions are drawn as follows:① The fracture number can make the post-peak failure stage of the stress-strain curve change from a rapid decline to a step down,and finally to a slow decline in horizontal extension,showing an approximate plastic flow deformation failure.In contrast,the effect of fracture aperture on the stress-strain curves of specimens is very small;② Influenced by the structural effect,the peak strength of specimens decreases with the increase of fracture number only under the condition of horizontal and inclined fracture.However,the fracture aperture has little effect on the peak-strength of specimens,and there is the weakest influence value;③ The fracture number has a great influence on the deformation characteristics of specimens under different fracture angles.However,the fracture aperture only has obvious influence on the deformation characteristics of the inclined fracture specimen;④ The effect of fracture number on the failure mode of the inclined and vertical fracture specimens is more obvious than that of the horizontal fracture specimen,but the influence law is not clear.Fracture aperture can completely change the failure mode of vertical fracture specimen and make it change from pure tensile failure to single shear failure,but it has little effect on the failure mode of horizontal and inclined fracture specimens.