Numerical Experimental Study On Filled Joint Shear Properties Based On PFC

The existence of joints destroys the integrity of the rock mass and affects the mechanical properties of the rock mass.For the open joint faces,a certain amount of fiIller is often accumulated,which makes the mechanical properties of the rock mass more complicated.In this paper,the discrete element software PFC is used to systematically carry out numerical experiments on the filling shear characteristics.The joint shear strength,crack development,failure mode and dilatancy effect were analyzed from three aspects of filling degree,filling material and joint surface morphology.It can provide reference for the physical experiment of filling joint chamber and the establishment of shear strength theoretical model.in accordance with.The main results are as follows:(1)For the regular zigzag joint surface morphology,the filling degree t/a(t is the filling thickness,a is the joint tooth height)is defined to reflect the filler thickness,and the influence of the filling degree on the filling joint shearing characteristics is analyzed.With the increase of filling degree,the shear strength shows a nonlinear decrease trend;the failure mode is gradually lbroken by the joint surface shear failure(t/a=0,0.5)and the wear and tear of the filler(t/a=1.1.5,2)Transformation;the dilatancy effect is gradually weakened.(2)For the regular zigzag joint surface morphology,the filling degree t/a(t is the filling thickness,a is the joint tooth height)is defined to reflect the filler thickness,and the influence of the filling degree on the filling joint shearing characteristics is analyzed.With the increase of filling degree,the shear strength shows a nonlinear decrease trend;the failure mode is gradually broken by the joint surface shear failure(t/a=0,0.5)and the wear and tear of the filler(t/a=1,1.5,2)Transformation;the dilatancy effect is gradually weakened.(3)The increase of the internal friction angle of the non-viscous filler under different filling degrees can increase the joint shear strength.The dilatancy effect is not obvious when the filling degree is less than 1.When the filling degree is greater than or equal to 1,the internal friction angle of the filler is gradually increased;the number of cracks generated during the shearing process is independent of the internal friction angle of the filler,and the degree of damage of the joint surface is independent of the internal friction angle of the filler.(4)The particle size of the non-adhesive filler has a great influence on the filling shear characteristics when the filling degree is greater than or equal to 1:the shear strength increases first and then decreases with the filler particle size of 0.5 mm;the dilatancy effect follows The filler particle size increases and increases;the larger the filler particle size,the stronger the rock-filler-rock interaction during shearing,and the more cracks are generated on the joint surface.When the filling degree is less than 1,the change in the particle size of the filler has no effect on the filling of the joint shear characteristics.(5)The increase of the undulation angle caused by the joint tooth width and the increase of the tooth height has the same effect on the shear strength and failure mode of the fill joint.When the fill thickness is small,the shearing strength of the fill joint gradually increases with the increase of the joint undulation angle.Increase;the number of cracks generated during the shearing process is increasing;the failure mode is gradually changed from slip wear to shear failure.The dilatancy effect is different:the dilatancy effect increases when the undulation angle is increased by the increase of the joint tooth width,and the dilatancy effect increases when the undulation angle increases due to the increase of the joint tooth height.When the filling thickness is large,the shearing characteristics of the filling joint are no longer affected by the morphology of the joint surface.