| With the rapid development of our national economy and the vigorously promote of the western development,the development and utilization of underground space will enter a new stage,and the transportation network is constantly improving,so the probability that the new traffic route cross the existing tunnel will be bigger,and the form of crossing is more complex,thus the construction site of new tunnel is inevitable will be near the existing tunnel.The construction of the new tunnel will cause second disturbance of both the soil and rock around tunnel,which lead to the tunnel deformation and the change of stress state,so without reasonable measures taken,which will have a very adverse impact on the existing tunnel.This paper takes the Pukou tunnel of the southeast part of the Fuzhou Beltway above cross the existing Jimian mountain tunnel of Wenfu part of the Hangzhou to Shenzhen railway as the engineering background,numerical analysis of the deformation and stress characteristics of the existing tunnel are taken in different spacing,cross angle and different hole diameter of the new tunnel condition,and then combine it with the measured data of Jimian mountain tunnel,so it provides guidance for the subsequent construction and design.Firstly,this paper expound the research results of adverse effects of the existing tunnels under the condition of different construction methods and different influencing factors,such as: the different distance of tunnels,the cross angle and the new tunnel diameter.Secondly,this paper introduces the surrounding rock stress field theory,and the mechanism between the new tunnel and the existing tunnel in the condition of different tunnel spacing,cross angle and the new tunnel diameter,as well as the control standard of the approach tunnel project construction and the approach level division grade,which lays a theoretical foundation for the research in the paper.Then,through the MIDAS/GTS finite element software to establish a three-dimensional finite element model to study the influence of the construction of the new tunnel on the deformation and stress of the existing tunnel in different cross tunnel spacing,different cross angles and different tunnel hole diameter condition.We get the distribution law of the deformation,additional tensile stress and additional compressive stress changes with various factors in the vault,arch foot,and the bottom corner of the upper and lower cross sections and the symmetry plane of the new tunnel due to deformation caused by excavation.The value of maximum additional tension and compression stress and its acting position are determined,and the range of the maximum additional tensile stress is determined to judge its stability.Finally,the monitoring data with time history of the vault settlement of the typical curve section and the axis section of Jimian mountain,and compare it with the results of numerical simulation to prove the reliability and accuracy of the deformation and stress law of Jimian mountain tunnel model.The research object is approaching cross tunnel engineering,which is common at home and abroad,related results can not only provide technical support for similar projects,also can provide a reference for similar projects in the future,it has a certain practical significance,and it can also provide reference and experience for the study of dynamic construction and design of tunnel. |
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