The Control Criteria And Engineering Exploration Of The Railway-bridge Transition Section Along The Line Of Nanjing-Qidong

Nanjing-Qidong railway is a single-track railway. The rapid development of theeconomy calls for the existing line to establish a double-track and railway speed increasing. Inrunning in the existing line, it is always met with the damage, especially in the transitionsection between the railway and the bridge. Due to the stiffness difference between thebridge and the railway, a huge settlement difference occurs, which greatly affects the lineirregularity and cause great damage to the subgrade within the scope of the transitionsection.Therefore, before the speed increasing, the carrying capacity of subgrade between thetransition section between the bridge and the railway along the Ning-qi railway, as well asthe track dynamics indicators,must be carried out through a careful research and made areliable assessment to make a preparation for the following reinforcement.The quality evaluation criteria of the existing bridge transition section target at the newline. In the transition section between the bridge and the railway along Ning-qi line. Thepassing train produces dynamic response differently due to the structure changes Therefore,the existing evaluation criteria is not fully applicable. The present study takes thereinforcement of the transition section within existing lines of the Nanjing-Qidong as theresearch object to establish a set of evaluation criteria through the numerical simulation, on-the-spot investigation and theoretical analysis. The present study also makes the comparisonand assessment between the evaluation criteria and on-site investigation data.1.The present study makes on the spot test of Evdvalue, N10value and Rayleigh wavevelocity values.After the measurement of the wheel/rail forces and the deflection value, thepresent study works out the railway stiffness.2.The present study makes use of the Ansys software, to establish two-dimensional finiteelement model, based on the structure size of the transition section between bridge andrailway along Ning-qi line, and the present study indicates the lateral distribution of thevertical dynamic stress on the surface of the railway subgrade and its internal verticalattenuation by the cross section model. The present study also indicates vertical dynamicstress acceleration and the dynamic displacement variation, due to the difference the subgradestiffness and the filling material stiffness in transition section. The present study make ananalysis of vertical dynamic stress acceleration and the dynamic displacement on the basis ofdifferent axle load and train speed.3.On the basis of finite element analysis,dynamic stress on the subgrade by on-the-spotinvestigation and calculation, the present study obtains the evaluation criteria of the transition section between bridge and the railway along ning-qi line. The evaluation criteria includes:Evdvalue, N10value and Rayleigh wave velocity values from the surface to the deep of the railsubgrade and track stiffness values and values of deflection.4.Compared with the evaluation criteria, the present study makes an evaluation of thequality of the transition section, and reach a conclusion as to whether it needs reinforcementor not.