Viscoelastic Analysis Of Surrounding Rock With A Non-circular Tunnel

In 2021,the Central Committee and the State Council issued the "National Comprehensive Three-dimensional Transportation Network Planning Outline",which puts forward new requirements for building a strong transportation country.The outline puts forward the need to promote high-quality development of comprehensive transportation and focuses on promoting safe development.As a kind of underground engineering,tunnels are widely used in railway and highway construction due to one characteristic,that is,not occupying ground surface area.Generally,when a tunnel is being constructed,relatively large deformation of the surrounding rock will occur.During the operation of the tunnel,the supporting structure may be cracked sometimes.This kind of deformation over time is generally caused by the viscoelastic characteristics of the rock mass.Therefore,it is very necessary to analyze the viscoelasticity of the tunnel.This paper firstly analyzes the elastic analytical solution of an unlined non-circular tunnel on the basis of the theory of complex transformation,using conformal transformation and Cauchy integral,and uses ANSYS software to carry out modeling and calculation,and compares with the analytical solution to verify the correctness of the analytical solution.Then on the basis of the elastic solution,using the elastic-viscoelastic correspondence principle,the analytical solutions of a variety of viscoelastic models were derived,and the analytical solutions of the Maxwell model and the Burgers model were summed up by using the FLAC3 D software.The comparative analysis of the numerical solution verifies the correctness of the analytical solution.Finally,using the FLAC3 D software,the viscoelastic numerical solution of the surrounding rock-support interaction considering the coupling of the stress release effect and the rheological effect of the rock mass is analyzed.The results show that for the non-elastic solution tunnel lining,the vertical displacement by the lateral pressure coefficient has little effects,and the hoop stress and increased with increasing lateral displacement of the lateral pressure coefficient increases,only in a specific position,hoop stress will decrease accordingly.For the viscoelastic solution of an unlined tunnel,the smaller the lateral pressure coefficient,the greater the change in vertical displacement with time.The common feature of the elastic solution and the viscoelastic solution of the unlined tunnel is that when the lateral pressure coefficient changes equally,the displacement also changes equally.For the viscoelastic solution of an unlined tunnel,the smaller the lateral pressure coefficient,the greater the vertical displacement of the arch top and arch bottom over time.And the longer the interval of applying the lining,the greater the displacement value would be.