Numerical Simulation Of Fluid-solid Coupling Analysis In Deep Buried Tunnel

With rapid development of China's various types of infrastructure construction recently,large-scale engineering related to tunnels have been shown the characteristics of super long and deep buried depth.The interaction between rock-soil and groundwater in the tunneling process is very complex,and study on their relationship is also quite complex and difficult.The analysis of fluid-solid coupling for deep buried tunnels has a vital role in guiding the construction for deep buried tunnel.The following work has been carried out in this thesis relying on the study on the second cascade hydropower station in Jinping.(1)High pressure infiltration instrument developed by Chengdu University of Technology was used to study the rock mechanics and permeability properties of the samples in Triassic Baishan marble:1)Compared to the uniaxial compression test,the elasticity modulus of rock samples changes little under high water pressure,but the strength of rock was nearly doubled.This phenomenon shows that the confining pressure has influence on rock strength,which can not be ignored.The use of high pressure strength on rock in engineering could be more effectively to reduce the cost and avoid waste.2)The permeability variation of different rock samples under different confining pressure is almost the same.The change rate of permeability under different osmotic pressure is slightly different.Variation of permeability coefficient of each rock with confining pressure and osmotic pressure were a quadratic polynomial relationship,but the mechanism of confining pressure and osmotic pressure affecting permeability coefficient is not the same,the effect of osmotic pressure is more important,more in line with the actual situation.3)Apart from the confining pressure and osmotic pressure,the changes of pores and fissures caused by the rock deformation are the root of the rock permeability changes.(2)CT scan was performed on permeability rock samples with micro fractures to observe rock fissure,which confirmed,that the interpretation of the permeability variation of micro fractured rock in high pressure permeability test is relative reasonable to a certain extent;(3)FLAC 3D simulation method was used to simulate the construction process of auxiliary hole.1)In the process of excavation,the seepage field changed significantly in tunnel,the pore water pressure decreased rapidly and the seepage velocity increased sharply around the tunnel.And the head of aquifer falling rapidly,which led to form a funnel to the center of the tunnel.2)Flow velocity in the front of face and tunnel hoop during tunnel excavation is larger,more likely to cause accident.Therefore,in the process of the tunnel excavation,stronger protective measures need to be taken when groundwater detecting.Furthermore,it also should be timely increase the grouting amount to prevent the occurrence of water inrush surge.3)The predicted water inflow in tunnel is broadly consistent with the water inflow of survey,which showed,the numerical simulation method is relatively accurate.4)During tunnel excavation,tunnel deformation caused by tunnel displacement increases in all directions.The deformation displacement of tunnel top is larger than both sides.Therefore,corresponding measures must be taken to control the development of plastic zone around the tunnel during the construction process.And the support should be focused on the tunnel top,in order to prevent the tunnel displacement evolving too large to result in rock falling,which would damage to the safety of the lives and property.