恒定法向刚度条件下加锚充填节理岩体剪切特性研究

Shear characteristics of anchored filling jointed rock mass under constant normal stiffness

深部岩体节理往往存在不同程度的软弱充填物质,导致岩体力学性质更为复杂。开展恒定法向刚度CNS边界条件下,考虑高初始法向应力及不同节理粗糙系数JRC−充填度△组合模式的加锚充填节理岩体剪切试验,结合微观电镜扫描(scanning electron microscope,简称SEM)分析充填节理部分宏微观结构演变特征,推导CNS边界条件下峰值剪胀角相关计算方法。研究结果表明:当△<0.5,试件剪应力强度呈现应力硬化;当1.0<△≤1.5,剪应力强度由基本恒定演化为应力软化。当△小于临界充填度△_(cr),JRC成为峰值抗剪强度主要影响因素。△在节理法向变形中起到控制作用,随着△的增加,出现剪胀、先剪胀后剪缩、剪缩3种演化规律,JRC则影响着试件剪胀−剪缩变化程度。充填节理部分破坏模式随着△的增加主要经历3个阶段:粗糙点磨平、充填物质摩擦、充填物质磨碎。微观角度下由疏松多孔结构形式演化为散体碎屑状结构形式。受挤压破碎区与挤压应力集中区二者的相互演化机制影响,锚杆剪切变形模式逐渐由△=0的“近似”拉剪变形向△=1.5的拉弯变形模式演变。在此基础上,提出了一种CNS边界条件下加锚充填节理岩体峰值剪胀角的计算公式,并进行了试验验证及边界条件影响参数敏感性分析。

The joints in deep rock masses often contain weak filling materials to varying degrees,which leads to more complex mechanical properties of the rock mass.A shear test on the anchored and filled jointed rock mass is carried out under the constant normal stiffness(CNS)boundary condition,considering the combination mode of high initial normal stress and different joint roughness coefficient(JRC)-filling degree△.The microstructure evolution characteristics of the filled joint part are analyzed by combining the microscopic scanning electron microscope(SEM),and the calculation method related to the peak dilatancy angle under the CNS boundary condition is derived.The research results show that when △<0.5,the shear stress strength of the specimen presents stress hardening;when 1.0<△≤1.5,the shear stress strength evolves from basically constant to stress softening.When △is less than critical filling degree △_(cr),JRC becomes the main influencing factor of the peak shear strength.△controls the normal deformation of the joint.With the increase of △,three evolution laws of shear dilation,first shear dilation and then shear contraction,and shear contraction emerge,and JRC affects the degree of shear dilation-shear contraction change of the specimen.The failure mode of the filled joint part mainly undergoes three stages with the increase of △:flattening of rough points,friction of filling materials,and grinding of filling materials.From a microscopic perspective,it evolves from a loose and porous structure to a granular debris-like structure.Affected by the mutual evolution mechanism of the extrusion crushing zone and the extrusion stress concentration zone,the shear deformation mode of the anchor gradually evolves from the“approximate”tensile-shear deformation at△=0 to the tensile-bending deformation mode at △=1.5.On this basis,a calculation formula for the peak dilatancy angle of the anchored and filled jointed rock mass under the CNS boundary condition is proposed,and the test verification and the sensitivity analysis of the influencing parameters of the boundary condition are carried out.