Excavation disturbance characteristics of strain softening surrounding rock under the attenuation effect of elastic modulus
After deep tunnel excavation,rock mass is prone to collapse and instability caused by severe deformation or rock burst disaster caused by block fragmentation,so the evaluation of disturbance characteristics of deep rock mass is of great practical significance to ensure engineering safety.The elastic modulus of rock is an important mechanical parameter that affects the degree of deformation after tunnel excavation.In this paper,through the mechanical response of peripheral rock in triaxial cyclic loading and unloading test in the established research,a nonlinear fitting method is used to construct a nonlinear drop model of rock elastic modulus,which can effectively reflect the change trend of elastic modulus under the influence of peripheral pressure and plastic strain.Based on the rock modulus drop model,the finite difference method is used to derive the numerical solution of the stress-strain field and displacement field of the strain-softened surrounding rock in deep buried tunnels.Combined with the numerical solution and according to the peripheral pressure and plastic strain on the peripheral elastic modulus or not,the influence of the critical softening coefficient and the quality of the surrounding rock on the distribution of the peripheral rock elastic modulus in the plastic region is analyzed,and the peripheral deformation law of the surrounding rock in the tunnels with different elastic modulus models is discussed.The results show that the deformation of the surrounding rock in the elastic zone is mainly affected by the peak modulus of elasticity,the modulus of elasticity changes nonlinearly in the plastic region,corresponding to the plastic softening stage of the change is faster and the amount of change is also larger,and the rate of change decreases sharply in the plastic residual stage,The modulus of elasticity tends to be stable,and reaches a minimum in the cave wall,the previous research method of elasticity of the modulus of elasticity is assumed to be the constant peak of deformation of the surrounding rock at the wall of the cave is small,and the safety of tunnel design is insufficient.
rock mechanicsdeep tunnelelastic modulusnonlinear dropstrain softeningfinite difference method
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