Reduction Of Train-induced Vibrations By Using An Isolation Trench

In recent years,the significant increase of train speed not only promotes the development of the regional economy along the railway greatly but also improves people's life significantly.However,the large-scale construction of high-speed trains not only brought benefits,but also brought some urgent problems,especially when the train speed approaches to the critical speed,the resonance phenomenon will take place.The isolation trench is easy to design and convenient to construct.Therefore,the study of reducing train-induced vibrations is of great importance.A coupled model of a track-layered elastic and saturated ground containing a wave barrier system is developed and the open and in-filled trench with rectangular cross-section serves as the barrier.The 2.5D indirect boundary element method is firstly proposed to obtain the flexibility coefficient of a layered ground including an isolation trench,then the track and the layered ground are coupled according to the equivalence between the deformation of the track and the vertical displacement of the layered ground on the center point of the track.The validity of the method is confirmed by comparing its results with published data,then numerical calculations are performed for the parameters of the trench under various soil conditions.For the model of a track-layered elastic ground system,this paper analyzes the isolation effect of displacement,velocity and acceleration by the open and in-filled trench at sub-,tran-and supersonic speeds,discusses several trench configurations,compares the isolation effect of a trench in a homogenous ground and in a single layered ground.Finally,the proposed method is used to investigate the isolation effect of the Swedish high-speed train X-2000 induced vibration at Ledsgard by using the trench.The results show that the isolation effects are different for different ground conditions and for different geometric parameters such as the depth,width and location of the trench.The analysis of the Swedish high-speed train X-2000 at Ledsgard which runs on soft soil shows that the isolation effect improves as the trench depth increases,and the trench isolates dynamic responses for the high frequency more effectively than those for the low frequency.For the model of a track-layered saturated ground system,this paper analyzes the isolation effect of displacement,velocity and acceleration by the open and in-filled trench at sub-,tran-and supersonic speeds,discusses the influence of trench depth,the porosity of saturated layer,the drained condition of the earth's surface and the materials of the in-filled trench on the isolation effect,compares the difference between saturated soil and dry soil,studies the influence of the stiffness ratio of bedrock to saturated layer on the isolation effect.The results show that the isolation effects of the trench on the layered saturated ground are better than that on the homogenous saturated ground;and the isolation effects of the trench on the homogenous saturated ground are better than that on the corresponding elastic ground.In addition,the trench detpth,the porosity of saturated layer,the stiffness ratio of bedrock to saturated layer and the materials of the in-filled trench have significant influence on the isolation effect of the trench.From the above,we obtain some conclutions which is of theoretical value in solving the problems of train-induced vibtations in engineering.