Research On Water-resistant Rock Mass And Failure Mode Of Karst Tunnel Face

Since the 21 st century,with the rapid development of China’s economy,infrastructure construction has also ushered in a period of rapid development.The construction of tunnels and underground projects in the western karst area has also increased.However,water and water bursts occurred during the construction of tunnels in the karst area.Mud geological disasters often occur,causing huge economic losses to the tunnel construction,seriously affecting the construction progress and threatening the safety of the construction personnel.This article uses a combination of a general model for preventing outbursts and numerical simulation to simulate the excavation process.The process of progressive destruction of the anti-projection body between the latent solution cavity in front of the palm face of the middle tunnel and the tunnel face.The main research results are as follows:(1)The factors influencing the breakthrough of the anti-outburst body are summarized: it is concluded that limestone is widely distributed in karst regions around the world and the lithology of water disasters is relatively high.According to the statistical results of the disaster-causing structures,karst caves are the geological bodies that have the most severe impact on tunnels during the construction of karst tunnels.(2)According to the type of surrounding rock structure between the disaster-causing structure and the tunnel excavation chamber,the types of anti-burst structures are divided into: complete structural anti-burst(complete structure,complete block structure),layered structure Outburst prevention body(layered block structure,layered fragmentation structure),intermittent structure anti-outburst body(inlaid discontinuous type,staggered intermittent type),fracture-type structure outburst prevention body(crack no filling type,crack filling Type),earth-rock type anti-outburst structure(fragmented fragment structure,mylonite dispersion structure),the corresponding failure modes of different types of anti-outburst bodies are: complete type(fracture failure),layered type(shear along the dominant surface)Shear failure),intermittent joint type(split failure),fissure type(split,shear failure),earth-rock type(overall slip,key block instability).(3)When the current karst water pressure in the karst cavity is used as a variable,the center position of the front of the palm face is relatively larger than the position of the vault and the bottom of the arch,The maximum displacement value decreases from the center line up and down.When the karst water pressure is sufficiently large,when the palm face is close to the front karst cavity,the palm face may be the first place to be penetrated by the karst water pressure.As the burial depth of the tunnel increases,the advancement of the palm surface causes the lateral extrusion displacement to transition from a single unloading to unloading,karst water pressure,and rock stratum original rock stress.Under the same excavation conditions and different burial depths,the burial depth The increase in the thickness of the anti-projection body will also increase,the unstable state of the anti-projection body will gradually appear with the burial depth,and the maximum displacement value of the palm surface block will also increase.Increasing the joint inclination angle of the anti-projection body will weaken the physical and mechanical properties of the rock mass.The more karst water will seep along the joint direction of the bedding layer,the minimum safety thickness of the anti-projection body will gradually increase with the increase of the joint inclination angle.The position where the protrusion was first broken from the front of the palm face continued to move downward as the joint inclination angle increased.(4)When the palm surface is far away from the front cavern,with the gradual increase of the cave cavity water pressure,tunnel burial depth,and joint inclination angle,the time point of the difference in displacement in the x direction of the monitoring point of the monitoring surface gradually advances,the same During the calculation period,the higher the joints at each point,the water pressure distribution at the monitoring points on the left side of the hydraulic pressure dissolution chamber is greater than the water pressure on the monitoring point on the right side of the palm face..