Study On The Tunnel's Three-dimensional Dynamic Response Under The Train Vibration Load

For reasons,the newly-built railways or tunnels need to step over the existing tunnel or railway closely.The train will produce a vibration load during travel,and the influences to the existing or newly-built tunnel from train vibration load becomes a focus of engineering construction.Currently,studies on the influence to surrounding structures from train vibration load is mainly focused on the buildings closely related to people's feel and interests or have strict vibration control standards,such as urban buildings,ancient buildings and precision experiment sites.There are few studies on the influence to hydraulic tunnel from train vibration load.Therefore,it is necessary to carry out studies on the lining's dynamic response,regularity of hydraulic tunnel and its vibration influence under train vibration load.With the Xiashen railway steps over the Sankesong Tunnel of Dongjiang Water Source Project as background in this thesis,the lining's dynamic response and regularity under single/double/quadruple lanes of train vibration loads are calculated and analysised.On the basis,the influences to the lining's dynamic response from tunnel's buried depths(20m,10m,5m)and surrounding rock's elastic modulus(30GPa,1.5GPa,0.045GPa)are discussed.Finally,the influences to the tunnel's structural safety from vibration load are evaluated from two aspects of stress and velocity.Through the studies of this thesis,the main results are as follows:(1)According to the deficiency that the train vibration load was assumed to be evenly distributed along the train in the studies of three-dimensional dynamic response in past,a new simulation and infliction method that the space distribution of vibration load can be considered is proposed,and a effective program of the train vibration load's simulation,positioning,applying is designed with APDL.(2)The calculation of the lining's dynamic response under single/double/quadruple lanes of vibration loads shows that:the lining's stress mainly appears in the vault and bottom plate,and mainly distributed in 10 meters of the track center's both sides;the variation of the lining's stress,displacement,velocity and acceleration time course is basically the same,and the time course can be roughly divided into three stages—the shock increase period(0?2s),the smooth fluctuation period(2?5.2s)and the shock decrease period(after 5.2s);the maximum value of the lining's responses usually occurs at the first period,and the vault's responses are the greatest because the vault are the closest to the ground track.(3)The calculation of the influences to the lining's dynamic response from buried depths and elastic modulus shows that:surrounding rock can reduce the load that transfer to the lining from the train,as the buried depths and elastic modulus decrease,the reduce effect decreases,thus the lining's dynamic responses will become greater,and the response's increase speed will be larger and larger.(4)The analysis of the influences to the tunnel's structural safety from vibration load shows that:for the tunnel which buried depth is about 10m,elastic modulus is below 1.5GPa and close to 0.045GPa,its maximum increase of the lining's dynamic stress can reache 33.59%,thus the tunnel's stress is greatly influenced by vibration load,and the stress may reach a high level under the vibration load and surrounding rock and lining's dead weight.The lining's dynamic responses caused by the vibration load have a certain regularity,the responses increase as the tunnel's buried depth and surrounding rock's elastic modulu decrease,and the influence to the tunnel's structural safety is affected by the buried depths and elastic modulus.The study results of this thesis can provide a reference for the construction of similar railway and tunnel intersecting project.In engineering practice,for the tunnel built in the surrounding rock which elastic modulu is low,the structural safety should be paid more attention under the train vibration load.