Longitudinal Analysis And Related Research Of Tunnel Support Based On Convergence-confinement Method

As a classic method for preliminary design of tunnels,convergence-confinement method is widely used in tunnels and underground engineering.However,the calculation accuracy and efficiency of convergence-confinement method still have much room for improvement,so this paper is based on convergence-confinement method and its related theory.According to the engineering geological conditions of the III,IV and V surrounding rocks of Caishenliang Tunnel,the method of solving the convergence-confinement method is studied by means of theoretical analysis,programming calculation and numerical simulation.The main contents are as follows:(1)According to the concept of virtual support force,the calculation formula of virtual support force under elastoplastic condition is derived,and the calculation formula of the unsupported LDP curve for the surrounding rock of Class III,IV and V of Caishenliang tunnel is obtained.Then,based on the relationship between the virtual support force and the unsupported LDP curve,the formula for calculating the virtual support force for the surrounding rock of Class III,IV and V of the Caishenliang tunnel is obtained.(2)Through the longitudinal analysis of the tunnel support effect,the distribution curve calculation formula of the radial displacement of the tunnel wall considering the virtual support force and the support resistance under the elastoplastic condition is obtained,and the function relationship between GRC,SRC and LDP curves is established through the correspondence,so that the function solution of the convergence-confinement method is obtained.Then according to the engineering geological conditions of the Class V surrounding rock of Caishenliang Tunnel,the parameters of support stiffness and support position are analyzed.The results show that the effect of support position is more obvious for the Class V surrounding rock section of the Caishenliang Tunnel than the support stiffness.According to this,it is possible to achieve a more economical support option.(3)According to the functional relationship between GRC,SRC and LDP curves,and according to the engineering geological conditions of the surrounding rock of Class III,IV and V of Caishenliang Tunnel,the Python program for solving the minimum support stiffness and its support position is realized.The ideal minimum support stiffness value of the Class III surrounding rock of the Caishenliang tunnel is 0.143 GPa/m,and the support position is about 2.4m away from the excavation face.The ideal minimum support stiffness value of the Class IV surrounding rock of the Caishenliang tunnel is 0.243 GPa/m,and the support position is about 0.4m away from the excavation face.The ideal minimum support stiffness value of the Class V surrounding rock of the Caishenliang tunnel is 0.299 GPa/m,and the support position is about 0m away from the excavation face.In summary,based on the analysis of the engineering geological conditions of the Class III,IV and V surrounding rock sections of Caishenliang Tunnel,the results of the theoretical solution are verified by comparison with numerical simulation and field measurement data,and preliminary analysis of the adaptability of the algorithm is carried out.In addition,the solution method and its applicability scope of this algorithm need to be further verified by engineering analogy and actual measurement.