Analysis Of Shear Failure Mechanism Of Anchorage In Irregular Filling Joint Surface

There are various kinds of rock masses in nature,which have extremely complex physical and mechanical properties.The existence of joints is an important factor in destroying natural rocks.With the rapid development of China's economy,the demand for the construction of underground engineering is consequently increasing.Therefore,the reinforcement of joints has become the focus of current scholars.At present,joints are usually filled and anchored to improve their shear strength.This paper summarizes the results of previous researches and studies the failure characteristics and mechanism of irregular filling joints through the combination of laboratory tests,numerical simulation,and theoretical analysis.The main research results are as follows:1.The results of the compression shear test are as below:the peak shear strength of the irregular filling joint surface is related to the roughness of the upper and lower joint surfaces.When the roughness of the upper and lower joint surfaces is close,the peak shear strength is higher.When the roughness of the upper and lower joint surfaces is different,the peak shear strength is lower,as the roughness of the upper and lower joint surfaces is not the same,bringing about uneven undulation of the joint surface,which results in the loose internal structure of the filling,the large undulation of teeth,and vulnerability to being cut up.These characteristics reduce its strength.While the upper and lower joint surface roughness are the same,the shape of the filling is regular,making its shear strength higher.2.Based on the compression shear test of the irregular filling and anchoring joint surface,the study draws the following conclusion;the peak shear strength of the irregular filling joint surface after anchoring is significantly higher than that before anchoring.In the process of shearing,the two sides of the filling first break,because the edge of filling suffers the outward extrusion pressure,resulting in the edge effect of the filling.As the shear proceeds,the filling material and the joint surface cement are damaged,and the joint surface begins to grind flat.At this time,the anchor bolt starts to play its role until the anchor bolt fails,and the whole shear process is then done.3.The shape of the filling material will have an impact on the reinforcement effect of the bolt,that is,the reinforcement effect of the bolt on the filling joint surface will be different due to the different roughness of the upper and lower parts.The specific performance is that when the roughness of the upper and lower joint surfaces is close to each other,the anchoring effect of the bolt is good,and the increment of the peak shear strength is obvious.When the roughness has a large difference,the anchoring effect of the bolt is poor,and the increment of the peak shear strength is relatively weak.4.There are three kinds of failure modes before anchorage:one is the failure of the interface between the filler and the joint surface,one is the failure of the filler,and one is the failure of the joint surface of the filler and the rock.Nonetheless,the failure process after anchoring is relatively simple,because the bolt completely connects the filler and the joint surface of the test block,and cooperatively resists the shear failure.Therefore,the failure mode usually performs as the test block,the joint surface and the filler are damaged together under the action of the bolt.5.Using particle flow numerical simulation software to model,observing,and monitoring the failure process of joints from the micro perspective,analyzing the micro failure process of the sample block through the particle displacement,contact force change,crack growth,cloud figure value,and internal stress change of the model.6.A new theoretical model of peak shear strength is improved by laboratory test and numerical simulation,according to the characteristics and mechanism of anchorage failure of irregular filling joints.