Study On Mechanical Properties Of Anchored Concrete Specimens

With the development and utilization of underground resources,in order to ensure the safety of operation,people support underground projects.At present,there are many forms of support.With the popularization of NATM,the effect of bolting and shotcreting support has been tested in underground engineering and other fields.In actual construction,the theory lags behind practice,and the design of bolt-shotcrete support parameters often fails to reach the optimum.The design theory of bolt-shotcrete support needs to be further improved.By making anchorage specimens to simulate the stress state of anchored rock mass,the mechanical characteristics of anchored concrete specimens in the process of loading are studied,and the relationship between the mechanical behavior of concrete and anchorage is analyzed,which provides a theoretical basis for promoting the application and development of anchor shotcrete support.The anchored concrete specimens of C20,C25 and C30 strength grades are designed and manufactured.Through uniaxial and triaxial compression failure tests,the deformation and failure process of the specimens and the relationship between strength and deformation parameters and confining pressure,anchorage force and concrete strength grade are studied and analyzed.The influence of anchorage on the failure and deformation process of the specimens is simulated and analyzed by FLAC3 D.It is helpful to analyze the failure mechanism of bolt-shotcrete support structure.The main conclusions are as follows:(1)When confining pressure is lower than 15 MPa,the compressive failure of specimens conforms to Mohr-Coulomb criterion,and the peak strength increases linearly with the increase of confining pressure.(2)The elastic modulus of anchorage specimens varies linearly with confining pressure,number of anchors and strength grade of concrete,but the greater confining pressure and anchorage strength,the smaller the increase of elastic modulus;the sensitivity of elastic modulus to anchorage strength is higher than that of concrete strength grade;cohesion increases with the increase of anchorage strength and concrete strength,while internal friction angle increases first with the increase of anchorage strength.The change law of the latter decrease.(3)Poisson's ratio is negatively correlated with confining pressure and number of anchors.With the reinforcement of anchorage,the expansion level increases gradually,and the anchorage delays the expansion point of specimens.(4)The joint action of anchorage and concrete specimens not only improves the strength ofthe specimens,but also has a significant difference in the distribution characteristics of shear strain between the anchorage specimens and the ordinary concrete specimens.The distribution and evolution of shear strain of the anchorage specimens are obvious.The numerical simulation results reveal the failure characteristics of the anchorage specimens.