Study On Transient Response Of Circular Tunnel Under Radial Non-uniform Load At Different Depth

In recent years,with the deepening of the study of dynamic response in tunnels,the theory of tunnel vibration response under axisymmetric loads has also tended to improve.However,in practical engineering,there are few internal loads that conform to perfect axisymmetry.Most of the loads transfer unevenly to the surrounding structures due to the different locations of the source,the structural forces near the source of load are more concentrated.Therefore,simply assuming the load as axisymmetric distribution is not entirely in line with reality.However,there are few studies on the vibration response of non-uniformly distributed loads,and the study of tunnel internal response caused by the non-axisymmetric and transient effects of loads is even less.In this paper,based on the existing theoretical framework,starting from the concentrated internal transient loads at both ends,theoretical analysis is carried out in tunnels under asymmetric loads with different buried depths.The main research contents are as follows:Based on the theory of elastic medium dynamics,a two-dimensional plane strain model of circular cavern is established by using wave function expansion method,and the dynamic response of circular cavern under transient radial non-uniform load is studied.The results of this study are compared with those of the related studies on the dynamic response of axisymmetric transient loads.The correctness of the proposed algorithm is verified.The effects of wave characteristics under radial non-uniform transient loads and shear modulus on the distribution characteristics of stress and displacement fields in radial and annular directions are analyzed.The results show that the peak position of the circumferential displacement response changes with time,and there is no extreme value in the constant position.Secondly,by means of elastodynamics-Hamilton theory,wave function expansion method and Laplace transform method,the numerical solution of stress and displacement field in twodimensional space in time domain is solved.The effects of relative stiffness of lining and soil,lining thickness and different angles on the dynamic characteristics of soil stress and displacement field and its fluctuation characteristics in time domain are analyzed.The results show that under the action of non-axisymmetric loads,the response attenuation of different locations varies with the increase of lining thickness,and the attenuation amplitude varies with the angle.The dynamic response of soil can be effectively reduced with the increase of lining stiffness,and the effect of vibration reduction is remarkable.Finally,the Graf coordinate conversion method is used to extend the whole space response in the soil to the semi-spatial response with the influence of buried depth and other factors.The non-uniform load response model of lining-soil semi-space tunnel is constructed.Then the frequency domain-time domain response curve is plotted,and the influence of tunnel depth,wave velocity,lining thickness,stiffness,load set degree and different angles on the dynamic response of soil is studied respectively.The results show that the influence of tunnel burial depth on the whole structure is different,and the amplitude of the soil at the top and bottom of the tunnel varies greatly.Because of the non-uniform load on the left and right sides of the structure and the concentration of stress,the response amplitude changes slowly under different burial depth.In this paper,three types of Tunnel-Tunnel response models under non-uniform transient loads are proposed.These models are suitable for the study of the mechanical response of tunnel under concentrated transient loads on both sides of the tunnel.At the same time,the study provides a new direction for the dynamic response of radial non-uniform loads.