Mechanical Response Of Roadway Surrounding Rock With Damaged Zone Under Dynamic Disturbance

In general,the surrounding rock of most roadways is damaged to varying degrees after excavation due to the influence of excavation methods,in-situ stress conditions,geological environment and other factors.In addition,the frequent action of external dynamic disturbances such as mechanical operation,blasting excavation and earthquake not only aggravate the damage of surrounding rock,but also easily induces the failure of underground roadways,including rock-burst,spalling,etc.,which seriously affects the safety and stability of the underground roadways.Therefore,knowing well the deformation and damage distribution of surrounding rock after excavation and the mechanical response of roadway with excavation damaged zone under dynamic disturbance are very important for roadway support design and disaster prevention and control.To this end,based on the relationship between damage of surrounding rock and stress variation in the surrounding rock after excavation,the presented study first considers the spatial distribution characteristics of surrounding rock damage,analyzing the distribution of surrounding rock with serious deformation and damage.Then,the dynamic response of roadway surrounded with damaged zone under dynamic stress wave is investigated by using theoretical analysis,numerical simulations and experiments.The influence of physical and mechanical properties of surrounding rock,the thickness of excavation damaged zone,the wave-number of incident stress waves,the curvature of wave-front,the incident direction,focal parameters,damage degree of surrounding rock,etc.,on the dynamic response of roadway are discussed.The specific research work has been conducted is as follows:(1)According to the stress distribution and variation characteristics of surrounding rock after excavation,considering the spatial variation characteristics of surrounding rock damage,the mechanical parameter representing the damaged surrounding rock is simplified as a function of r along the radial direction.The roadway models with ‘elastic-plastic’ and‘elastic-plastic-fracture’ deformation in the surrounding rock in the uniform and non-uniform stress fields are established,and the expressions for obtaining damaged zones in surrounding rock are derived and verified.Based on the above expressions,distributions of excavation damaged zones in the surrounding rock of circular roadway in uniform and non-uniform stress field are discussed.(2)Based on the understanding of damage distribution in surrounding rock and the law of stress wave refraction and reflection,the stress wave scattering model of roadway with excavation damaged zone is first established,and the dynamic stress distribution around the damaged roadway under the action of steady-state plane stress wave is analyzed.Then,the dynamic stress distribution near the damaged roadway under transient plane stress wave is further obtained by using the steady-state response results and Fourier transform.The influences of rock parameters in each deformation zones,thickness of excavation damaged zones,incident stress wave number and other parameters on the dynamic stress distribution of surrounding rock are discussed.(3)To study the dynamic stress distribution of roadway with excavation damaged zone under adjacent dynamic disturbance,the dynamic disturbance from the adjacent area is simplified as the incidence of cylindrical stress wave,and the cylindrical wave scattering model of the damaged roadway is also established.The dynamic stress distributions around the damaged circular roadway under steady-state and transient cylindrical waves are analyzed,and the influencing factors,including mechanical parameters of surrounding rock,incident wave number,thickness of excavation damaged zone,etc.,are discussed.Furthermore,the dynamic stress distributions around the damaged roadway under cylindrical wave with different wave front curvatures are presented.Using the geometric relationship between source-roadway distance and transverse dimensions of roadway,the definition conditions of plane stress wave and cylindrical stress wave are determined.(4)Using spectral element method(SEM),the dynamic response around the circular roadway with excavation damaged zone under the action of stress wave is numerically simulated,and the scattered wave field distributions,maximum particle velocity,particle vibration frequency,dynamic stress concentration and particle displacement distribution are obtained.In addition,according to the relationship between the distribution of excavation damaged zones and the lateral pressure coefficients,the dynamic responses around the circular roadway with different shape of damage zones under stress wave are analyzed,and the influences of the incident direction of stress wave,focal parameters,etc.,on the dynamic response around the roadway are discussed.(5)By using model simplification,the circular roadway with excavation damaged zone is first simplified as a hole rock specimen with damaged surrounding structures,and then the specimen is dynamically loaded by split Hopkinson pressure bar(SHPB).Based on the experimental results,the mechanical properties of roadway with damaged zone as well as the evolution process of surrounding rock fracture are indirectly analyzed.The influences of damage degrees of surrounding rock on the dynamic response of roadway is discussed.Based on this and the relevant results presented in this thesis,some support suggestions for the prevention and control of dynamic disasters appeared in underground roadways are put forward.