Evolutionary Mechanism Of Mud Bursting Through Water-inrich Fault In Tunnels And Engineering Applications

The focus of traffic infrastructure construction shifted to the midwest in China.Because of the complicated and changeable geological environment,it is inevitable to meet the adverse geologic structure,such as faults,karst caves,underground river and so on,in the construction of tunnel and other underground engineering.Therefore,collapse,water inrush,mud burst and other geological disasters are very likely to occur.This seriously threatens the safety of tunnel constructors,and causes equipment abandonment and construction delay.It makes a great economic loss to our country.Faults is one of the most important disaster-caused structures in the tunnel construction process.The researches about mechanism of mud burst in tunnels are deficient,compared with the relative mature study of the law of water inrush catastrophe evolution in coal mines.Therefore,it has important practical significance to research the mechanism and to realize the advance alarm and prevention of mud bursting in the construction process of tunnels across the water-rich and fractured weak fault zones.In this paper,the main research object is the mechanism of mud bursting in tunnels across the water inrich mud-filling and fractured weak fault zone.Based on the comprehensive treatment engineering of mud bursting in the fault F2 of Yongliang Tunnel of Jilian Highway in Jiangxi province,the characteristics of filling medium in the water-rich mud-filling and fractured weak fault zones has been studied deeply,by theoretical analysis,laboratory tests,model tests and numerical simulations.Meanwhile,the process of the mud bursting under construction disturbance has been studied and the engineering early warming mechanism has been established.There are some research achievements which possess a certain theoretical value and engineering significance to the tunnel construction,the research results mainly including:(1)The impacting factors leading to disaster of water inrush and mud burst in tunnel are studied,and the occurrence conditions and the controlling factors of mud bursting disaster in water-richen fault tunnel are revealed.Based on the geomechanical characteristics and hydrogeological characteristics of fault zones and characteristics of internal filling media in fault zones,the laws of water filling,conducting or wate inrush occurred in fault zone with different fault structures is summarized and the mechanical model of tunnel in the fault zone with water-richen is established.(2)The rheological properties testing of faulted mud were conducted,then the relationship equation of rheological parameters and water content and temperature of fault mud is obtained,and the constitutive model related to water content and temperature of fault mud was established.Meanwhile,the generality and rationality of the relation curve equation and correctness of constitutive model related to water content and temperature of fault mud is verified by model tests and numerical simulation.(3)A large scale three dimension model test system for water-richen fault zones tunnels is developed.It consists of model test frame,CNC hydraulic loading system,constant pressure water supply system and multi information monitoring system.The stress distribution and deformation law in surrounding rock during the process of water inrush and mud bursting is revealed through series of model tests study on tunnel construction in the condition of water-richen fault zones.The evolution of multi information such as temperature,displacement,stress,strain and the amount of mud is obtained and the disaster process of tunnel water inrush and mud burst is simulated.(4)The water inrush and mud burst occurred during excavation of tunnel in water-richen fault zones is investigated through the method of hydro-mechanical coupling numerical simulation.And two important characteristic parameters which are critical distance and water pressure respectively are introduced to determine the disaster criterion of tunnel water inrush and mud bursting.It is of great significance for the prediction and forecast tunnel water inrush and mud bursting.The effect of water pressure in fault and disturbance due to blasting on critical distance in mud bursting and variation of mud burst amount with time were analyzed.Eventually,the result of numerical simulation was verified through the monitoring data in engineering site.(5)The feedback system of real-time monitoring information and emergency response strategy in tunnel construction process was established.The optimum escaping road during mud bursting was studied and determined.The early warning system of disaster is improved and a disaster prevention and rescue strategy is formulated which provide great significance and guidelines to the prevention and control of the mud bursting disaster in the tunnel construction.