Study On Interaction Mechanism Between Accumulation Slope And Parallel Tunnel Under Rainfall

Limited to the overall planning of traffic routes,some mountain tunnels need to pass through the accumulation layer slope.The slope of the accumulation layer has loose structure,strong permeability,and is susceptible to construction disturbance.The disturbance of tunnel excavation and rainfall infiltration in the operation process can lead to the extrusion deformation of the accumulation layer slope,increase the pressure of the surrounding rock of the tunnel and lead to the cracking of the lining,which affects the safety and normal operation of the project.How to ensure the stability and safety of the tunnel crossing the accumulation layer slope and how to put forward reasonable stability analysis and design methods and safety control standards have become one of the key problems that need to be solved urgently in engineering construction and operation.This paper,by the zhangjiajie in Hunan province mountain tunnel of an expressway as the engineering prototype,using the finite element analysis software to establish the three-dimensional numerical model,deposit in parallel through tunnels under the condition of rainfall and slope interaction mechanism as the research content,based on field monitoring results,combining traditional mechanics theory and numerical simulation method.The influence law of the deformation and extrusion pressure on the bearing deformation characteristics of the adjacent tunnel supporting structure under rainfall condition is discussed,which lays a foundation for the study of the stability of the slope and tunnel supporting structure.The research contents are as follows:(1)Based on the analysis of the site monitoring results,it can be seen that the accumulation layer slope shows obvious signs of creep deformation under the effects of tunnel excavation and unloading disturbance,and the accumulation layer slope is in a state of extrusion deformation.At the same time,the deformation process of the interaction between the accumulation layer slope and the parallel tunnel is summarized.(2)The finite element analysis software was used to establish a three-dimensional numerical analysis model of the project.The excavation process of the tunnel was simulated by using the method of three-step excavation with reserved core soil.The temporal and spatial distribution of displacement and internal force between the accumulated layer slope and the adjacent tunnel at different construction stages was analyzed by the numerical simulation method.It is concluded that the excavation disturbance of the accumulation soil in the excavation area of the tunnel is one of the main external causes of the deformation of the slope body and the adjacent tunnel,and the accumulation slope body is more sensitive to the excavation disturbance than the bedrock,and is more prone to damage.(3)Based on the model set up different rainfall intensity and rainfall duration,through comparative analysis of rainfall and rainfall between different working condition of rainfall and slope and tunnel supporting structure stress and displacement and so on,it is concluded that rainfall than without rainfall accumulation slope parallel to the adjacent tunnel supporting structure stress and deformation increases significantly,and with the increase of rainfall duration,rainfall intensity increases.These effects are even more pronounced.