Study On Diffusion Law And Mechanics Behavior Of Grouting Reinforcement Of Surrounding Rock For Neighborhood Tunnel In City

Neighborhood tunnel is characterized by the small thickness of the middle rock wall,which is a structural type between the two-hole separated tunnel and the multi-arch tunnel.Because of the small thickness of the middle rock wall,it is easy to be destroyed,so it is very important to ensure the integrity of the middle rock wall.However,neighborhood tunnel has the advantages of easy line extension,low construction difficulty and shorter construction period.Therefore,in urban areas limited by terrain,neighborhood tunnel construction can be used.However,there are still many key technologies to be solved in the construction process.Engineering analogy is mainly used in domestic design.The basic theory of tunnel structural mechanics and surrounding rock elastoplasticity is not mature at home and abroad.Therefore,it is necessary to strengthen the research of neighborhood tunnel.Firstly,the diffusion characteristics of grouting slurry around the whole section of a tunnel with small net distance are studied theoretically in this paper.Secondly,the displacement,stress and plastic zone of the characteristic points around the tunnel before and after grouting reinforcement with radial bolt and grouting reinforcement with small conduit are studied,and the protective effect of grouting reinforcement on surrounding rock is discussed.Through systematic theoretical and numerical research,the mechanism of grouting reinforcement and the effect of improving tunnel stability are further analyzed and understood.The main contents of this paper are as follows:(1)The diffusion rule of grout in single grouting pipe under disturbance stress and grouting pressure of surrounding rock is revealed,and the diffusion characteristics of grout in surrounding rock during grouting around whole section are further studied.By means of numerical simulation,the effect of grouting diffusion around the whole section of tunnel with small net distance under different grouting time is discussed.(2)The mechanical behavior of neighborhood tunnel excavation can be seen as the interaction between the superposition of mechanical behavior of two single tunnel and the excavation of two single tunnel.However,the interaction of mechanical behavior of neighborhood tunnel is related to many factors.Therefore,this paper studies the influence of burial depth,net distance and lithology on the mechanical behavior of neighborhood tunnel excavation.(3)The analysis model of bolt grouting reinforcement for radial system of neighborhood tunnel is established.The displacement and mechanical changes before and after grouting for radial system bolt are calculated.The horizontal,vertical displacement and stress variation characteristics of characteristic points around tunnel are mainly analyzed.At the same time,the protective effect of grouting around tunnel on ground subsidence is analyzed.Based on the change of plastic zone around the tunnel before and after grouting reinforcement with radial bolt,the protective effect of grouting reinforcement on surrounding rock is discussed.(4)Based on the differential equation of grouting slurry diffusion control in tunnel surrounding rock,numerical simulation was used to study the diffusion characteristics of grouting slurry in advance small conduit of three-dimensional model,including the relationship between grouting circle thickness and grouting time.Then,an analysis model of neighborhood tunnel reinforcement by advanced small-pipe grouting is established.By analyzing the changes of displacement,mechanics and plastic zone around the tunnel before and after the neighborhood tunnel reinforcement by advanced small-pipe grouting,the influence of grouting reinforcement on surrounding rock is discussed.