Numerical Analysis Of The Asymmetrical Pressure On A Tunnel Embedded In Geologically Bedding Strata

In the mountain tunnel construction process, usually the tunnel will pass through the layered rock . It is a difficult problem to analyse and calculate the pressure on the lining and the safety of the structure.With the help of theoretical analysis and finite element method , the thesis studies the calculation method for asymmetric pressure on single-line railway tunnel embedded in geologically bedding strata , and the factors of layer thickness and inclined angle on asymmetric pressure.The thesis studies the following aspects:(1) Based on the study of certain literature , the thesis gives the loads distribution on the lining structure in geological bedding strata, with a certain assumptions, and there will not exist asymmetric loads unless inclined angle greater than the friction angle of the bedding plane.(2)The thesis simulates the bedding surface with sandwich element and contact element method respectively,finding the results the thicker the layer,the smaller the error. With the increase of the inclined angle,the error of two models is decreased,and then increasing.The error of sandwich element is is greater than the contact element,but is acceptable in engineering error range. The thesis simulates the joint with sandwich element method.(3)With a certain clined angle,the load on the left wall is greater than the right wall.With the increase of the layer thickness,the losd on the vault trends to a constant value,but the wall will bear a more asymmetric load.(4)With the increasing of the inclined angle,the asymmetric load on the lining structure is increasing , and then decreased,which attain its ultimate when inclined angle ranges between 45 and 55 degree.(5)The inclined angle has role on the lining structure.With the increasing of the inclined angle,the moment on the vault is positive,and then negatively increasing.The moment on the left wall attains its ultimate when the inclined angle is 55 degree.The difference of moment on the spandrel attains ultimate when inclined angle is 45 degree.(6)There are some measures to decrease the harm of asymmetric load applied by geologically bedding strata , such as section asymmetric design and asymmetric reinforcement for the lining structure,anti-slide pile,bolting,prestressed anchor, multi-support and drainage measures for the layered rock.