不同充填度对节理剪切破坏机理的影响

Influence of different filling degree on failure mechanism of rock joint

岩体的力学性质主要受制于节理的力学性质,而节理充填物对节理的力学性质有较大影响。为研究节理充填物厚度对节理力学性质的影响,采用水泥砂浆制作不同充填度的规则人工节理进行剪切试验,并采用PFC(Particle Flow Code)数值模拟软件研究该节理的破坏机理。试验与数值模拟结果表明:随着法向荷载和充填度的增大,节理峰值剪切强度增大,剪胀特性减弱;随着起伏角的增大,节理峰值剪切强度增大,剪胀特性增强。在节理剪切过程中,充填体首先发生破坏,此后再产生剪切断裂和剪胀破坏。在不同的法向荷载、充填度和起伏角条件下,节理破坏为滑移破坏、剪切断裂破坏和拉伸断裂破坏3种,低法向荷载和低起伏角时,滑移破坏为主,拉伸断裂发生于起伏角较大的节理中,而剪切断裂破坏多以节理和充填体共同破裂组成,发生于法向荷载与充填度均为中等大小的情况。当充填体厚度与齿形凸起高度相当时,节理破坏主要为充填体剪切破坏。

Mechanical properties of rock mass are mostly controlled by rock joint,and the joint filling has great influence on the mechanical properties of rock joint.In order to study the effect of filling thickness on shear properties of rock joints,a series of regular artificial joints were made in concrete and experiments of direct shear were conducted under constant normal stress.Failure process of filled joints were analyzed by PFC (Particle Flow Code).Experimental and numerical results show that the shear strength increases but the dilatancy decreases with the increase of normal stress and filling degree.The shear strength and dilatancy increase with the increase of undulating dip angles.The joint filling fails firstly during the shear process and is followed by the shear failure of undulates and joint dilation.With the increase of joint filling degree,the peak shear strength and dilatancy are decreased.The failure mechanism of joints involves slip failure,shear failure and tensile failure under different conditions.Slip failure is dominant under low normal load and low fluctuation angle.Tensile fracture occurs in joints with large undulating angles.The shear fracture failure mainly occurs when the normal loads and filling degrees are at medium level.Shear failure happens in the filling when the thickness of filling body is equal to the height of tooth.