Mechanical Properties And Safety Evaluation Of Invert Structure In High-speed Railway Tunnel

High-speed railway tunnel are faster speed,large cross section,more intense of structural vibration,higher durability compare with general speed railway tunnel.During the high-speed railway tunnel construction,floor heave of tunnel invert disease is an important factor affecting the safety of tunnel construction;during the train operation,under the combined action of static load form surrounding rock and dynamic load from train,The destruction of tunnel invert is likely to expand rapidly which will influence the safety of train operation.However,due to the differences of cause,processes,mechanisms and degree of the destruction,there are significant differences in the influence of tunnel construction and train operation safety,making the safety control of the invert and the effect differ greatly.For this series of problems,firstly,according to the failure mode of high-speed railway tunnel invert,failure mechanism and evolution law of the bottom heave is studied and the influencing factors are analyzed;Secondly,based on the mechanism of vibration wave propagation,the tunnel invert dynamic response and attenuation rule is clarified;finally,the method of safety evaluation of high-speed railway tunnel invert is put forward.The main work and research results are as follows:(1)The destruction evolution rule of high-speed railway tunnel invert is studied,from the stress characteristics and failure modes point of view,the basic mode of the bottom heave failure of tunnel invert is put forward,which are respectively,the bending-tension-crack type,the bending-shear-crack type and shear dislocation type,and the corresponding failure mechanism is revealed.For the bending-tension-crack type,it is mainly bending failure,focusing in the middle span;for the bending-shear-crack type,it is mainly bending-shear failure,focusing in the arch foot,for the shear dislocation type,it is mainly shear failure,caused by shear failure of surrounding rock.(2)The mechanical model of the coupling between the load structure model and the stratum structure model is established,the numerical solution of the internal force field of invert is obtained and the logarithmic spiral equation and the solving process of the internal force field of invert are given.According to the ranking of deformation degree of invert based on orthogonal test,the deformation prediction model of high speed railway tunnel is established,the representation and calculation formula of deformation effect of invert floor heave are obtained and the design principle of high speed railway tunnel invert is given.The high-speed railway tunnel invert floor heave is divided into three levels:slight,moderate and severe with a specific criteria for each grade.(3)The interaction model of train-track-invert is established,the vibration characteristics of the inverted arch structure under the action of high-speed train are analyzed based on the numerical calculation and field test.The vibration response of structure is divided into advanced vibration,the vibration when train pass through and the vibration after the train pass through.The main factor of vibration disease is the vibration when train pass through.The dynamic response rule of invert and its filling layer under the action of train vibration load is given.It is found that the vertical vibration acceleration and dynamic stress response are inversely proportional to the depth,but proportional to the speed of the train.It is pointed out that the invert and its filling layer are the main carriers of the train vibration load.(4)The propagation law of the crack of high-speed railway tunnel inverted arch structure under the combined action of static load from surrounding rock and dynamic load from train and It is pointed out that the crack under the action of static load from surrounding rock have a rapid expansion when it encounter the dynamic load from train.The calculation method of fatigue life of invert is presented based on the study on fatigue cumulative damage.(5)The design principle of high speed railway tunnel invert is given.The safety analysis model of high speed railway tunnel invert is established.The evaluation model is proposed,which is based on the three aspects,including the surrounding rock properties of the tunnel and the inverted arch structure,the static response,the dynamic response.A comprehensive evaluation system is established,which includes 7 basic indexes,including failure mode,uplift displacement,crack opening,crack depth,crack length,vibration acceleration and vibration damage.The method of safety classification of tunnel invert,which is divided into A,B,C three security level and according to different level,different control measures will be taken.The method has been successfully applied in the project of Fu Chuan tunnel.