Experimental Study Of Tensile-shear Damage Of Brittle Rock With Anchors Under Cyclic Disturbance

The complex mechanical environment of three “high” and one “disturbance” in the deep environment makes the mechanical phenomena of deep rocks different from those of shallow ones and cannot be accurately controlled.It induces impact ground pressure,tension-shear damage of rock in the disturbed area and other tension disasters.Meanwhile,it induces anchors to form tension-shear damage and fracture failure,which greatly affects the safety of construction in deep brittle rocks and increases the difficulty and resistance of protection against brittle rock disasters.In this paper,with the support of the National Natural Science Foundation of China project(51674116 and 51904101)i carried out a study on the tensile shear failure of brittle rock specimens with anchors under cyclic disturbance.The study was carried out to provide theoretical support for the application of anchor support in the support of deep brittle surrounding rock masses.The main contents and conclusions are as follows:(1)According to the tensile-shear failure characteristics of anchor rods in deep brittle surrounding rocks,the Z-shaped member is used as the tensile shear failure model,and the gypsum solution,lead wire and epoxy resin adhesive are used as raw materials to make the anchor brittle rock specimens that can effectively simulate the comprehensive tensile shear failure rupture of deep brittle surrounding rocks.(2)Tensile-shear damage tests were carried out on brittle rock specimens under different anchorage conditions in static and cyclic perturbation loading,and the analyses were carried out from the perspectives of bearing capacity,crack extension evolution,final rupture mode,displacement-deformation characteristics and anchor failure mode of the anchored brittle rocks.The test results show that: the anchor rod has a significant effect on the load carrying capacity and deformation capacity of brittle rocks under static loading and disturbance,and delays the crack generation.Meanwhile,the peak deformation time of brittle rocks usually corresponds to the peak load time.Under static loading,there is no obvious post-peak feature in unanchored specimens,and there is a period of load stabilization in anchored specimens because the anchor rod gradually becomes the load carrying body.(3)The crack evolution process of brittle rock specimens shows that: all brittle rocks eventually undergo tensile-shear damage and form closed tensile-shear circular cracks.As well as,the moment of crack emergence varies with the loading condition;under static loading conditions,tensile-shear cracks are produced before the peak load;and under cyclic disturbance conditions,cracks are produced at the stage of disturbance load application.(4)Acoustic emission monitoring equipment was used to collect AE events of brittle rocks under different anchorage conditions and loading conditions,and to conduct comparative analysis from the perspective of the basic acoustic emission parameters and their correspondence with the rupture failure of brittle rocks.The AE signals showed that,the cyclic disturbance load increased the average energy of individual impacts of brittle rocks and the peak ringing count,cumulative ringing count,peak energy and cumulative energy of brittle rocks under the same anchorage conditions.At the same time,the change of loading conditions significantly affected the percentage of cumulative ringing count of AE at the moment of crack initiation of brittle rocks.The AE parameters of anchored specimens were much larger than those of unanchored specimens under the same loading conditions.