Numerical Analysis Of Stability Of Underground Tunnel Under Stress Wave

As a fully buried underground structure,the stability of underground tunnel under earthquakes is more complicated than that of structures on the ground.On the one hand,the seismic wave is complicated in characteristics and directly acts on the surrounding rock of the underground cavern.The stability of the underground tunnel performs differently under different types of stress wave.On the other hand,structural planes distributed in the underground rock mass greatly affects the propagation of the seismic wave,especially in the fault zones formed by fractured rocks,which might causes serious risk of earthquake damage and affects the stability of underground tunnel.Therefore,it is necessary to understand the influence of stress wave and fault structure on the dynamic response of underground tunnel under the earthquake,so as to effectively carry out the safety assessment of underground engineering to improve the stability of underground cavern.In this study,taking the stress wave reflection at ground surface and rock stratification into consideration,a tunnel model with discontinuous-jointed rock mass is established in the Universal Distinct Element Code(UDEC),and the dynamic response of the tunnel is studied numerically.First,the effect of the amplitude and frequency of the longitudinal wave and shear wave on the dynamic response of the underground chamber is studied respectively.The peak particle velocity,displacement response and acceleration response of the surrounding rock under varying stress waves are obtained.Simulation results show that the dynamic response of tunnel under earthquake is positively correlated with the amplitude of stress wave and negatively correlated with the frequency of stress wave.Then,the effect of fault properties,including the fault-tunnel distance,fault dip angle,hanging wall effect and fault stiffness,on the dynamic response of underground tunnel is further studied,focusing on the peak particle velocity,displacement and settlement,and stress change in the surrounding rock mass.Simulation results show that the fault intensifies the dynamic response of the tunnel under the earthquake.The distance between the fault and the tunnel,as well as the dip angle and the position of the fault both have a significant impact on the tunnel dynamic response.The fault with relatively stiffness has a more obvious impact on the dynamic response of the tunnel under earthquake.The influence of the stress wave and faults on the dynamic response of underground tunnel is systematically studied and summarized in this thesis,which provides suggestions to the development of sustainable underground space.