Semi-analytical Solution And Applications Of Stress And Strain Caused By Excavation Of Multi-tunnels

Abstract:With the development of subway construction, the subject about the excavation of multi-tunnels has attracted more and more attentions. Due to the interaction between neighboring tunnels, the stress and strain in the surrounding rock of multi-tunnels are different from those of single tunnel. Therefore, it is necessary to carry out researches on the multiple tunnels.Based on the national key scientific research project, the thesis studied related problems caused by the excavation of multi-tunnels, such as the distribution characteristics of stress and strain field, the settlement on the ground surface and so on. The results of multi-tunnels with different configurations were obtained by complex variable method. The main achievements and conclusions are as followings:(1) The complex variable theorem and conformal transformation method and their application in solving the elastic mechanical problems of infinite half plane with circular hole(s) are introduced. The physical meanings and derivation of relative formulas are explained in details. The adoption of Schwarz’s alternative method in solving the problem of doubly connected domain is simply introduced, while the using of this method for problem of multiply connected domain is promoted.(2) Based on the complex variable method and Schwarz’s alternative method, the calculation functions is deduced by coordinate transferring, then the stress and displacement in the infinite half plane when excavating several tunnels at the same time is possible to be solved.(3) Using the mathematical software, the functions have been compiled into the Matlab program, so that the subsidence of ground surface in the excavation of double tunnels and triple tunnels under different buried depths and clear distances can be calculated. With the calculation results, the distribution and variation principles of ground subsidence are analyzed.(4) The fields of stress and strain in the surrounding rock caused by the excavation of parallel twin tunnel are modeled by finite differential software FLAC3D. Using the modeling results, the characteristics of the stress and displacement around the excavated tunnels can be reflected. Moreover, comparing the results from the present theoretical method and the traditional method on the basis of modeling results, the reliability of theoretical method has been be testified.(5) The monitoring data of ground subsidence during the shielding of twin tunnels are statistical analyzed. According to the settlement characteristics, some measurements are proposed including soil conditioning and shield parameter controlling. Based on the works of others, the thesis promoted the complex variable method in solving the problem of multiple tunnels excavated in the elastic medium. The results and conclusions have important academic value and can be provided as a theoretical reference for elastic deformation of multiple tunnels.