大理岩规则齿形结构面剪切特性试验研究

Experimental study of shear deformation characteristics of marble dentate joints

为了便于研究不同粗糙度结构面岩体在压剪荷载作用下的剪切强度、剪切变形等力学特性的变化规律,制作了3种具有不同起伏高度的大理岩规则齿形结构面,锯齿高度分别为0、1、3 mm,开展了不同法向应力下的结构面直剪试验。试验结果发现,结构面剪应力-剪切位移曲线可分为两类:滑动破坏型和峰值剪断型;结构面沿锯齿先爬坡后剪断的破坏过程可划分为4个阶段:压密闭合阶段、爬坡剪胀阶段、锯齿剪断阶段、挤压碾碎阶段;锯齿结构面剪切强度-法向应力曲线近似呈三段线的特征,建立了三线段剪切强度准则;锯齿结构面剪切刚度-法向应力曲线呈上凸型特征,提出了结构面剪切刚度模型公式;锯齿结构面法向位移-剪切位移曲线呈先剪缩后剪胀的变化特征,提出了评价剪胀特性的经验公式。

This study is aimed to investigate the regularities of the shear strength, shear deformation and other mechanical properties of joint rock mass with different roughnesses under compression-shear stress. Marble specimens were prepared with the dentate height of 0, 1 and 3 mm, respectively. Then direct shear tests were conducted on the marble specimens under different normal stresses.Experiment results show that curves of shear stress and displacement can be divided into two types: sliding failure type and peak shear type. The climbing-gnawing process of joints goes through four stages: the compaction stage, the climbing stage, the saw-tooth cutting stage and the completely crushing stage. The curves of shear strength with the normal stress of the dentate joint present more obviously three-segment line feature, and a trilinear shear strength criterion is established. The curves of shear stiffness with normal stress present a convex type, and a shear stiffness model is put forward. The dilatancy curves of dentate joint present firstly shear contraction and then shear dilation, and an empirical formula for evaluating shear dilation is proposed.