| Deep rock masses are subjected to complex environmental factors such as high stress,high temperature,high pressure,and disturbance during the mining process.These complex environmental factors can lead to intense stress concentration,crack propagation,deformation amplification,and increased damage in deep rock masses.As a result,the stability and bearing capacity of the support system of underground tunnels or chambers can be compromised,leading to extensive deformation and damage of surrounding rock masses and posing a threat to the safety of underground engineering.Therefore,investigating the mechanical characteristics and energy damage evolution mechanism of deep anchoring rock masses is of great significance for deep underground engineering.This paper investigates the reinforcement effect of CFRP circumferential reinforced rock of a tunnel at a depth of 800 meters,which approximates the effect of rock reinforcement by anchor spraying.By conducting triaxial loading and cyclic loading-unloading tests on the CFRP circumferential reinforced sandstone,the corresponding stress-strain curves are obtained.Through comparative analysis of the mechanical properties and energy dissipation evolution of the two stress paths of sandstone under different reinforcement schemes and confining pressures,the reinforcement mechanism and energy conversion mechanism of the CFRP material are revealed.Furthermore,a triaxial energy damage equation considering the reinforcement effect is established.The main research results are as follows:(1)The circumferential reinforcement of CFRP can effectively improve the strength deformation parameters and shear strength parameters of the specimen,and they increase correspondingly with the increase of the reinforcement area.The reinforcement effect is ideal,and the initial damage caused by the bolt can be avoided reasonably.(2)The analysis of energy confining pressure effect shows that confining pressure has a significant influence on energy evolution.With the increase of confining pressure,the total energy,elastic energy and dissipated energy gradually increase,indicating that confining pressure can well enhance the energy storage capacity of specimens and improve mechanical properties,and rock failure requires more energy.(3)With the increase of CFRP reinforcement area,the total energy,elastic energy and dissipated energy all increase gradually,and the damage variable decreases gradually,which indicates that CFRP circular reinforcement can reduce the dislocation between grains of rock mass and restrain the development of cracks and damage of rock mass,which is the essence of constraint reinforcement.(4)The use of axial stress increment well reflects the energy increase with the increase of stress in the pre-peak stage and the energy evolution in the process of bearing capacity recovery from the post-peak stress drop to the residual stage,which verifies the rationality of axial stress increment for the energy evolution in the cyclic loading and unloading process.(5)Based on the energy dissipation theory,the energy damage equation of sandstone under triaxial loading considering the reinforcement effect was derived,and the experimental data and literature reference curves were substituted to verify that the derived equation could better describe the energy damage evolution of CFRP during the cyclic triaxial loading process of reinforced sandstone. |
