Study On Tunnel Face Stability And Prereinforcement Measures In Rich Water Fault Tunnel

Because of the linear requirement of the tunnel engineering,the highway tunnel inevitably passes through the bad geological zone,such as the fault zone.The quality of the surrounding rock is poor,the tunnel excavation is easy to cause the instability of the palm surface,especially the water rich fault tunnel.Because of the seepage force,the tunnel face is more prone to instability and damage.Therefore,it is of great theoretical and practical significance to study the stability and pre-reinforcement measures of the tunnel face crossing the water rich fault tunnel.In this paper,the numerical analysis model is established by ABAQUS finite element software,and the influence of permeability coefficient,cohesive force and the support force on the stability of the palm face is studied.On this basis,the supporting effect of the pre-reinforcement measures based on the new idea method is studied.The main research results of this paper are as follows:(1)Aiming at the problem of tunnel face instability in the tunnel crossing the fault fracture zone,this paper studies the factors that affect the stability of the palm surface(permeability coefficient,cohesive force and the supporting force of the palm face).The calculation shows that the length of the incidence of the maximum extrusion displacement of the permeability coefficient is the same as the cohesion force.The incidence of Permeability coefficient is more advanced than cohesive force.(2)The support force perpendicular to the surface of the palm is applied before entering the fault zone.When the support ratio is 2.5,the displacement of the palm face is greatly reduced and the incremental displacement is hardly produced.(3)On the basis of the study of the factors affecting the stability of the surface of the palm,the pre-reinforcement measures(pre-grouting,face anchor bolt and front pipe roof)based on the new method are studied.The calculation shows that the pre-grouting improves the quality of the surrounding rock of the excavating body,reduces the permeability coefficient of the excavating body,and reduces the extrusion of the palm face.There is a Marginal utility on the effect of the advance bolt effect,that is,the face anchor bolt can greatly reduce the extrusion displacement of the palm face in a certain length range,and the contribution of the length to the extrusion displacement of the palm face is not significant;the effect of the front pipe roof on the settlement of the arch top and the surface settlement in front of the palm is obvious.(4)When unsupported and front pipe roof support,when the palm face is closing to the stratum interface,the plastic zone appears first in the stratum interface.The plastic zone appears at the interface between the grouting area and the fault fracture zone,and appears ahead of the palm face.