| In order to shorten the traffic time,we can not only increase the train speed,but also reduce the operation distance.Tunnel construction is an effective means to reduce the operation distance and improve the speed.In recent years,the terrain of tunnel construction has become more and more complex,the requirements of tunnel structure have become higher,and the demand has become larger and larger.Unfavorable conditions such as deep burial,high geostress,high water pressure,large deformation,cold,high altitude and so on have emerged in endlessly.In the process of tunnel excavation and operation,the analysis of tunnel stress and surrounding rock has always been a hotspot and difficult topic in the field of tunnel construction.Current research mainly focuses on numerical simulation based on monitoring data and model test with specific engineering background,while analytical theory research is limited to circular tunnels,and the research on arbitrary shape tunnels is still less.In this paper,these problems above are put forward as a new research direction.The grouting and frost heaving problems encountered during the excavation and operation of non-circular tunnels are studied from theory to practice by theoretical analysis,monitoring data and numerical simulation.The main research contents and achievements are as follows:(1)By introducing the optimization method,the mapping functions of non-circular tunnels considering the inner boundary of lining and the contact boundary between lining and surrounding rock are derived.Furthermore,the mapping function of non-circular tunnel considering the inner and outer boundary of lining and the boundary of grouting ring or frost heave ring is derived.(2)An elasticity analytical method of stress and displacement for single non-circular lining under stress boundary conditions is established by introducing the theory of complex variable function.Application of MATLAB calculation software to solve elastic analysis examples which are considering only stress and displacement of a single non-circular lining.The results show that the complex power series method can successfully solve the stress and deformation problem of a single non-circular lining.(3)In this paper,the finite-domain problem considering only the single lining ring structure is connected with the infinite-domain problem,and the analytical method of stress and displacement considering the interaction between lining and surrounding rock is deduced.Then the analytical solution and numerical simulation results are compared and analyzed to evaluate the rationality and accuracy of the analytical solution.(4)Based on the complex function theory,the stress and displacement of non-circular tunnel considering grouting reinforcement are analyzed,and the analytical solutions of stress and displacement of non-circular tunnel considering grouting reinforcement are derived.The numerical solution obtained by Flac finite-difference software is used to check the analytical solution.It is found that the analytical solution agrees well with the numerical solution on the inner boundary of lining,but there is a certain deviation in the stress concentration at the shoulder and foot of tunnel arch.After grouting,the stiffness of grouting ring increases,the deformation decreases and the integrality increases,which improves the stress condition of lining structure.On the outer boundary of lining,the analytical solution agrees well with the numerical solution,but there is a deviation in normal deformation when α equal to 80 degrees and 120 degrees approximately.The peak circumferential stress of lining decreases by about 8.9%when α equal to 80 degrees.(5)An analytical method for stress and displacement of non-circular tunnels under frost heaving is proposed.Based on this method,frost heaving displacement boundary conditions are derived first.Then,the derived frost heave displacement boundary conditions are connected with the finite domain represented by lining and the infinite domain represented by surrounding rock respectively through continuous boundary conditions,and the elastic analytical solution of frost heave force of non-circular tunnel with lining-frost heave ring-surrounding rock system is derived.And it is validated by numerical simulation.(6)The stress release coefficient is introduced into the stress and displacement problem of non-circular tunnel under frost heaving of surrounding rock.Based on the displacement boundary condition and stress release coefficient,the elastic analytical formula of frost heave force of non-circular tunnel with lining-frost heave ring-surrounding rock system is deduced again.(7)Comparing the analytical solution with the numerical analysis result,it is found that the analytical solution is in good agreement with the numerical solution.The frost heave force of surrounding rock has obvious influence on lining,and the additional circumferential stress caused by frost heave at vault,arch foot and arch bottom increases significantly.The circumferential stress of vault increases from 1.35 MPa to 3.67 MPa.The circumferential stress at the arch foot increases by about 104.3%compared with the circumferential stress without frost heave.The circumferential stress of arch bottom increases from 0.1 MPa to 2.0 MPa.(8)Applying the proposed method to the analysis of engineering examples,it is found that the stress release conditions are closer to the actual working conditions.Although the theoretical calculation results are based on the elastic theory and the construction factors such as excavation,blasting and equipments are not taken into account in the calculation process,which leads to some discrepancies in the quantitative values between the two calculation results,the theoretical results are still representative,and the deformation law reflected by them conforms to the objective engineering practice. |
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