Study On Time Lag Effect Of Water Inrush In Fault Fractured Zone Of Deep-buried Tunnel

The water inrush disaster is one of the major disasters in the process of tunnel construction.When the tunnel construction passes through the water-rich fault fracture zone,lagging water inrush often occurs due to the interaction of excavation disturbance and groundwater heave.However,the lagging water inrush has been a difficult point in research because of its large water inrush,high degree of damage,and difficulty in accurate prediction.Correct understanding of the mechanism of tunnel fault lagging water inrush is the basis for reducing and controlling the occurrence of major geological disasters and ensuring the safety of tunnel construction.In this paper,numerical analysis and model experiments are used to study the effects of different structural structures,aquifer water pressure,initial permeability,fault width and fault dip on the hysteresis of water inrush,and some preliminary conclusions have been obtained:(1)The filling structure composed of soil skeleton(fixed particles),movable particle phase and water phase was constructed by using CFD software Fluent to simulate the fault structure.The migration of water phase in different filling structures was studied.The distribution of water phase in different filling structures was obtained,and the variation of seepage time with initial water velocity and dynamic viscosity was obtained.(2)Based on the Darcy-pde coupling equation,the seepage process of the fractured rock mass is analyzed,and the variation law of porosity,seepage velocity and water inflow during the seepage process and the distribution of the seepage channel during the seepage process are obtained,which lays a foundation for the further study of the mechanism of lagging water inrush in fault fracture zone.(3)Based on the Richard equation and the Darcy equation,the multi-field coupling software COMSOL is used to establish the lagging water inrush model of the tunnel fault fracture zone.The hysteresis water inrush process is analyzed,and the variation of effective saturation and water pressure in the water inrush process is obtained.The effects of aquifer water pressure,initial permeability,fault width and fault dip angle on the lagging time of water inrush are studied,which provides a useful reference for revealing the mechanism of fault lagging water inrush.(4)A three-dimensional tunnel model test system under large rainfall and groundwater seepage is developed.The model test system is mainly composed of model box,loading system and data acquisition system.For the first time,the system is used to carry out the fault lag effect of the water inrush in the fault fracture zone.The variation law of osmotic pressure,earth pressure and displacement during loading and excavation was obtained,and the hysteresis of water inrush in tunnel fault fracture zone was verified.