Research On Creep Properties Of Quartz Sandstone And Rock Burst Control Under Dry And Saturated Conditions

In order to study the mechanism of water spray softening or high pressure water injection softening for rock burst control,this paper takes quartz sandstone in deep cavern as the research object.Firstly,indoor rock creep tests under graded loading are carried out on dry and saturated specimens,supplemented by acoustic emission equipment for real-time monitoring.Based on the test results,the creep mechanical model is established by introducing fractional calculus,and Levenberg-Marquarat algorithm and Universal Global Optimization algorithm are integrated to fit the creep test results so that the parameter identification results are obtained.The physical and mechanical parameters and creep model which obtained from the test are introduced into the finite element numerical model,and the simulation of chamber excavation is carried out under different water content states and different water temperatures,so as to calculate and analyze the rock burst tendency.The results are as follows.(1)The water content state has a significant influence on the failure mode of creep rock.Specifically,with the increase of water content rate,the failure mode transfers from shear failure to splitting failure,and both the main control surface and the weakening zone are obvious.Under the condition of saturated water,the axial deformation of quartz sandstone is less than that in the dry state due to the interaction between axial pressure and pore water pressure.The results of real-time acoustic emission test show that the presence of water has a significant impact on the occurrence time of acoustic emission events,which manifests that the behaviors of crack propagation and penetration mainly occur in the later stage of loading.(2)The creep behavior of rock can be better described through introducing the creep mechanics model which is established by fractional calculus.The parameter identification results show that rock viscosity is enhanced and the characteristics of damage and hardening are obvious after the specimen saturated,and the evolution processes of internal microcracks slow down at the moment of loading and creep stages.(3)In the finite element model,to calculate respectively the rock burst tendency of chamber excavation under different water content states and different water content temperatures,we find that the control of water spraying for rock burst is the result of combined effect of softening surrounding rock and decreasing temperature.It is considered that low temperature will induce the surface shrinkage of surrounding rock and further release surface energy,so as to reduce the rock burst intensity.