| With the rapid development of China’s economic strength,tunnel construction technology is developing rapidly and the number of double tunnels is gradually increasing.The construction of the vehicular crossings between the double tunnels will inevitably disturb the main tunnel and affect the stability of the rock around the tunnel cavern when excavating due to the crossover with the main tunnel route.If the excavation method and the form of support are inappropriate,the settlement of the vault is likely to increase,affecting the construction schedule and causing large economic losses.Therefore,the excavation and support of the intersection section between the main tunnel and the vehicular crossing should be given more attention,as appropriate excavation methods can enhance the stability of the tunnel surrounding rock and ensure the smooth progress of the construction schedule.This paper presents a numerical simulation analysis of the construction of a large section of the main tunnel and the intersection of the carriageway in the context of the Hot Spring Fort Tunnel,and investigates the effect of the tunnel excavation method and slurry reinforcement support:(1)Through a large number of domestic and international literature,the main strength theories and common intrinsic structure models of rocks were summarised,and suitable theoretical bases and mechanical intrinsic structure equations were selected from them,which laid the theoretical foundation for the numerical simulation study in this paper.(2)Based on the engineering background of the intersection of the main tunnel and the vehicular crossing at the Hot Spring Fort Tunnel,three excavation methods,namely the twostage method,the middle door method and the three-stage method,were simulated and analysed by using MIDAS/GTS software.The results of the simulations were compared in terms of vertical displacement,horizontal displacement,plastic zone,maximum principal stress and minimum principal stress,in order to find the optimum excavation method for the cross section.The results of the numerical simulation show that the two-stage method has the best control over the stress difference between the left and right sides of the cross section,the horizontal displacement difference and the plastic zone,and that the construction method is simple and the construction period is short,which is conducive to ensuring construction safety and quality and the successful completion of the construction schedule.(3)The MIDAS/GTS software was used to optimise the spraying parameters for the initial support of the tunnel,and to study the deformation and stress of the surrounding rock under different thicknesses and strengths of shotcrete,resulting in the optimum spraying parameters of 30 cm thickness and C30 strength;to ensure the stability of the surrounding rock in the cross section of the tunnel,the surrounding rock was reinforced by grouting,and by establishing grouting reinforcement circles of different thicknesses and strengths,the study By establishing grouting rings of different thicknesses and strengths,the effect of different grouting parameters on the stability of the tunnel surrounding rock was studied,and the optimum grouting parameter for the stability of the surrounding rock was found to be 1.0m in thickness.This paper investigates the construction technology of the intersection section of the main tunnel and the vehicular crossing,and provides a reference for the design and construction of similar tunnels. |
