Grouting Reinforcement Mechanism And Application Of Shallow Buried Small Clear Distance Tunnel Under Complex Urban Environment Conditions

With the rapid development of urban underground space in China,the underground space structure is intensive,resulting in complex and variable strata.To further save urban underground land,most urban shallow tunnels are designed as Neighborhood Tunnel,but Neighborhood Tunnel are more complicated in the stability of the septum pillars than separated.tunnels,which makes the stability difficult to control.If preventive measures are not taken,it will cause serious disasters such as roof collapse or even collapse.Based on the Neighborhood Tunnel of Jinan Yuhan Road,this paper analyzes the stability of the septum rock pillar before and after reinforcement by means of physical simulation test and numerical simulation of simulation software,and studies the instability and failure characteristics of the Neighborhood Tunnel.I n order to provide theoretical and experimental basis for similar tunnel projects in the future.The specific research conclusions are as follows:The plastic zone of the rock pillar in Neighborhood Tunnel can be divided into three parts: non-affected zone,weakly affected zone and strongly affected zone.The influencing factors of the overlying pressure of the surrounding rock of the small clearance tunnel are analyzed,and the stress state of the surrounding rock is determined.The small clearance tunnel is divided into three functional zones: upper rock disk,middle rock disk and lower rock disk.Through the indoor simulation test of Neighborhood Tunnel,the stress characteristics and deformation damage of Neighborhood Tunnel and the surrounding rock of the tunnel during excavation are studied.The stress variation law of the rock pillars in the tunnel before and after grouting is analyzed.It is found that the bias effect is common in the excavation process of Neighborhood Tunnel.Combined with the failure characteristics of tunnel under gradient loading,it is verified that the grouting has a significant improvement on the stability of tunnel surrounding rock and septum.Using finite difference numerical simulation,the deformation and displacement of the septum rock column before and after grouting are analyzed.The instability characteristics of the septum rock pillar during excavation are studied,and the stability of the septum rock pillar is obtained.Influencing factors.The reinforcement of the septum rock pillar has a significant effect on the deformation of the surrounding rock of Neighborhood Tunnel,which is beneficial to the stability of the tunnel.Based on the above research,the research results are applied to the urban engineering of Neighborhood Tunnel in Yuhan Road,Jinan.According to the different functional divisions of the septum rock pillar,different grouting treatment measures are proposed.By comparing the physical model test with the numerical simulation results,it is verified that the grouting reinforcement has a significant effect on the stability improvement of the septum rock pillar,and provides practical guidance for grouting for similar Neighborhood Tunnel.