During the excavation of deep rock,a sudden change in boundary conditions will cause the in-situ stress on the excavation surface to release instantaneously.This disturbance propagates in the form of an unloading stre...During the excavation of deep rock,a sudden change in boundary conditions will cause the in-situ stress on the excavation surface to release instantaneously.This disturbance propagates in the form of an unloading stress wave,which will enlarge the damage field of surrounding rock.In this paper,the dynamic unloading problem of the insitu stress in deep rock excavation is studied using theoretical,numerical,and experimental methods.First,the dynamic unloading process of rock is analyzed through adopting the wave equation,and the equivalent viscous damping coefficient of the material is taken into consideration.Calculations show that there is significant tensile strain in the rock bar when the strain rate is above 10^-1 s^-1.With an increase in the length or damping coefficient,the wave state will change from an underdamped to an overdamped state.Second,implicit and explicit solvers of the finite element method are employed to simulate rock unloading processes,which can be used to verify the theoretical results from one-dimensional to three-dimensional stress states.Finally,the dynamic unloading experiment of a onedimensional bar is used to further verify the validity and accuracy of the theoretical analysis.展开更多
基金The research work has received funding from the National Natural Science Foundation of China(Grant Nos.51479147,51779193).This work was supported by the Major Program of Technological Innovation of Hubei Province(Grant No.2017ACA102).
文摘During the excavation of deep rock,a sudden change in boundary conditions will cause the in-situ stress on the excavation surface to release instantaneously.This disturbance propagates in the form of an unloading stress wave,which will enlarge the damage field of surrounding rock.In this paper,the dynamic unloading problem of the insitu stress in deep rock excavation is studied using theoretical,numerical,and experimental methods.First,the dynamic unloading process of rock is analyzed through adopting the wave equation,and the equivalent viscous damping coefficient of the material is taken into consideration.Calculations show that there is significant tensile strain in the rock bar when the strain rate is above 10^-1 s^-1.With an increase in the length or damping coefficient,the wave state will change from an underdamped to an overdamped state.Second,implicit and explicit solvers of the finite element method are employed to simulate rock unloading processes,which can be used to verify the theoretical results from one-dimensional to three-dimensional stress states.Finally,the dynamic unloading experiment of a onedimensional bar is used to further verify the validity and accuracy of the theoretical analysis.
