Study On Mechanical Behavior Of Anchored Rock Mass And Action Mechanism Of Rock Anchor

Prediction of rock mass instability and damage and fracture mechanism are one of the important problems to be solved in rock mechanics research,and tensile failure and shear failure are common failure forms that cause rock mass instability.Accurate and reliable control method of roadway surrounding rock is the core of theory and technology to ensure the stability of surrounding rock.In order to realize accurate anchoring technology of surrounding rock,the influence of tension-shear failure of rock mass with different anchoring parameters was explored.In this thesis,the red sandstone is taken as the research object,and the red sandstone is selected as the anchoring matrix to carry out the prefabricated anchor rod.The Brazilian splitting test and variable angle shear test are carried out on the anchor body,and the acoustic emission software is used to monitor it.The influence mechanism of the difference of anchoring parameters on the failure characteristics,tensile strength and shear strength of sandstone during the fracture process is analyzed.The damage evolution of rock is further discussed,and the acoustic emission characteristics and damage evolution law of rock are revealed.The test method and research results of this thesis can provide certain theoretical reference value for monitoring the instability and failure of surrounding rock mass and controlling the stability of surrounding rock mass.The main conclusions are as follows:(1)In the Brazilian splitting test,it is found that the full-length anchoring method can improve the tensile strength of sandstone specimens more obviously,and the strength improvement rate reaches 39.77%.By increasing the pretightening force of the end anchor specimen,it is found that increasing the pretightening force of the anchor can improve the tensile strength of the specimen and inhibit the development of microcracks in the specimen to a certain extent.When the pretightening force reaches 1N·m,the strength improvement rate reaches 28.92%.By comparing and analyzing the test results,the optimal tensile anchorage mode is obtained,the relationship between tensile strength and anchorage parameter difference of sandstone is revealed,and the influence mechanism of anchorage parameter difference on failure characteristics and tensile strength of sandstone is analyzed and discussed.(2)Through the variable angle shear test.From two aspects of shear strength and deformation characteristics,the Coulomb yield conditions of sandstone and crack propagation and failure modes during shear failure are described and analyzed in detail,and the evolution of shear strength and failure modes of sandstone under different anchoring parameters is summarized.(3)By analyzing the distribution of acoustic emission characteristic parameters in tension-shear fracture mode of sandstone under different anchoring parameters,the internal relationship between fracture damage law of sandstone and acoustic emission in tension-shear fracture mode can be revealed.(4)By using PFC particle flow simulation program,Brazil disk model and variable angle shear test model were built,and the loading failure process of Brazil splitting test and variable angle shear test was simulated,and the stress-strain curves of the two types of test models were obtained.The fracture characteristics and force chain network distribution in the two types of models were studied and analyzed from the aspect of meso-particle failure characteristics,revealing the meso-mechanism of mechanical behavior of sandstone specimens in the process of tension-shear failure.