| As a key controlling project of the transportation network,tunnels play an irreplaceable role in engineering construction.In the actual construction of the tunnel,various types of unfavorable geological bodies are often encountered.Among them,the fault fracture zone is a more typical type.Compared with ordinary surrounding rock,the continuity of the rock mass in the fault fracture zone is generally poor,with obvious pores and cracks,low strength,unable to form an effective bearing arch,and accidents such as large deformation or even collapse during construction.Therefore,it is of great significance to analyze and study the stability of the tunnel surrounding rock in the fault fracture zone.In view of this,this article takes the Mianjiu(Mianyang-Jiuzhaigou)high-speed Wulipo tunnel as the relevant background,and comprehensively uses multiple methods such as theoretical analysis,indoor model test and numerical simulation to study the tunnel crossing different dip angle Dip,different thickness W and different The deformation and force law of surrounding rock in the fault fracture zone inclined to Dd is analyzed,and the control effect of surrounding grouting reinforcement is analyzed.The main results are as follows:(1)The cause and geological type of the fault are pointed out,the key factors affecting the stability of the surrounding rock in the fault area and the corresponding deformation and failure characteristics are explained,and the main criteria for the stability of the surrounding rock are summarized.(2)In the indoor model test,there is a very obvious difference between the vault and the side wall on the influence range of surrounding rock deformation,that is,the attenuation rate of displacement change is different,which is mainly reflected in the slow attenuation of vault displacement along the radial direction,while the rapid attenuation of side wall.In addition,the existence of fault greatly weakens the spatial constraint effect of surrounding rock in tunnel face area,and makes the radial displacement and pressure change of surrounding rock at each measuring point of section 2(in fault)increase significantly compared with Section 1(before fault)and section 3(after fault).(3)In this paper,FLAC 3D finite difference software is used to create three-dimensional numerical models of tunnel excavation under different fault forms,and the control variable method is used as the main research method to obtain the influence of different fault dip angle,fault thickness and fault tendency on surrounding rock displacement,plastic zone and contact pressure.(4)Through orthogonal test,the most significant factors of tunnel deformation affected by different fault shapes in the process of tunnel excavation are studied.The results show that:the thickness of fault has a very significant effect on the vault settlement,followed by the inclination of fault;the inclination of fault has the greatest effect on the horizontal displacement of side wall,followed by the thickness of fault.From the overall displacement level,when the fault dip changes between 0 ° and 45 °,it has no effect on the vault settlement and the horizontal displacement of the side wall.(5)The results show that the displacement control effect is very significant when grouting reinforcement is carried out in fault area,in which the maximum settlement of vault is reduced by 21.57%,33.18% and 39.17% respectively;the horizontal displacement of side wall is reduced by 26.56%,42.11% and 50.19% respectively,while the maximum settlement of arch crown is reduced by 21.57%,33.18% and 39.17% respectively When grouting reinforcement is carried out before and after entering the fault,the effect of displacement control is general,especially the effect of horizontal displacement is not obvious.(6)By introducing the average value k of surrounding rock deformation control rate,the final control effect of surrounding rock radial deformation under different grouting reinforcement thickness is quantitatively studied.It is found that when the thickness of reinforcement circle is 1 m,the mean value of displacement control rate is small,and the effect on displacement limit is limited.When the thickness is 3 m,the mean value of deformation control rate of surrounding rock is the largest,but compared with the thickness of2 m,the increase range is not large.Therefore,on the premise of ensuring safety,in order to avoid excessive waste,it is suggested that the thickness of reinforcement ring should be 2m. |
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