Study On The Mechanical Behavior And Failure Mechanism Of The Fractured Surrounding Rock By Grouting Reinforcement

With the development of transportation infrastructure in China,especially the construction of key projects such as "Belt and Road" and "Sichuan-Tibet Railway ",a large number of tunnels and underground projects will pass through adverse geological areas such as fault fracture zone or fractured rock mass.Influenced by seismic wave or construction rate,large deformation and high deformation rate occurred in the adverse geological section will become one of the key problems restricting the whole project construction process.To solve the above mentioned problem on site,reinforcing the adverse geological section by grouting is always the main technical measure.However,it remains inconclusive on how to analyze the mechanical properties of grouting reinforcement body subjected to seismic wave or construction,and how to evaluate the effect of grouting reinforcement on the fractured rock mass,which become general concerns to the engineering community at present.In this article,laboratory test,numerical modeling and theoretical analysis were combined to study the static and dynamic mechanical characteristics of fractured rock mass by grouting reinforcement.The main conclusions are as follows:(1)First,the test system for grouting and strengthening of fractured rock mass with controllable crack inclination angle and width was developed.Then,the static and dynamic properties of grouting reinforcement body were measured,and the relationship between dip angle,width,grouting material and mechanical properties of the crack was established.In addition,the optimal grouting material for fractured rock mass under compression and tension loading was also obtained.(2)By means of high-speed camera technology,the crack initiation,propagation and failure characteristics of grouting reinforcement body were analyzed.The relationship between fractal dimension and mechanical properties of grouting reinforcement body was established using fractal theory.(3)Based on the failure characteristics of the grouting reinforcement body,the collapse model of the kind of buckling model of pressure bar and the shear failure model were established.According to the fractal characteristics of grouting reinforcement body and the energy dissipation principle of single crack,a fracture-damage model of micro-crack was established.(4)The characteristics of the micro-crack distribution of grouting reinforcement body were analyzed.In addition,the evolution of stress-strain field and energy-dissipation distribution of the specimens following the kind of buckling model of pressure bar and the shear failure model were analyzed,so as to explain the failure mechanism of grouting reinforcement body upon loading.(5)Dynamic properties of grouting reinforcement body under different strain rates were measured,and they are explained from the perspective of stress-strain field,energy distribution law,and micro-crack distribution characteristics.(6)Based on the fuzzy hierarchy method,the evaluation system of surrounding rock grade of grouting reinforcement body was established,where the dip angle of fractured rock mass is considered.Through engineering and numerical simulations,the relationship between fracture inclination and compressive strength,and the availability of the evaluation system of surrounding rock after grouting were verified.