Settlement Monitoring And Mechanism Analysis Of Railway Road Bridge Transition Section In Loess Area

In this paper,a transition section of a road and Bridge in GanNing section of YinXi railway is selected as the research object.The settlement monitoring and measurement guidance scheme of the transition section of the road and bridge is systematically discussed.The settlement calculation method of the transition section,the settlement calculation method of the transition structure itself and the prediction method are discussed in detail.Through the on-site monitoring data,the five sections of the bridge abutment,the bridge abutment at 5m,the bridge abutment at 12.5m,the bridge abutment at 20 m,and the bridge abutment at the loess area are separated from the single settlement and cumulative settlement respectively.The settlement mechanism was analyzed in detail in three aspects including the settlement rate,and the conclusion was drawn: The initial settlement of the cross section of the road and bridge in the loess area is faster,the settlement is larger,and it gradually slows down in the later period,and finally stabilizes;along the line direction,the settlement value does not change much from the abutment to the 5m abutment,and then it is inverted trapezoid Within the length of the transition section structure(approximately 5m to 20 m away from the abutment),the amount of settlement becomes larger and the rate increases.At a distance after the inverted trapezoidal transition structure,the settlement rate becomes smaller and the settlement,the change is not large,and the settlement is stable when the transition to the subgrade is completed.Using GM(1,1)to predict the measured data and carry out precision test,it can be seen that the GM(1,1)model based on the gray theory can effectively predict the settlement of the road and bridge transition in the loess area.The ABAQUS software was selected for the numerical simulation of settlement,and a construction design model,a positive trapezoidal transition structure model,a transition section model with a design slope of 1: 2 and a subgrade model without a transition structure were established respectively.The influence mechanism of Elastic Modulus of foundation,different filling materials,transition structure and design slope on settlement of the road and bridge transition section is analyzed.Through the comparison between the measured value and the simulated value,it is found that although the numerical simulation value and the actual observation value are somewhat different,the waveform of the settlement curve is consistent.It can be seen that the model under this setting can simulate the settlement mechanism of the road and bridge transition.In actual monitoring,due to the frequent influence of external working conditions,its value will become larger,deviate from the settlement curve under the action of constant load,and approach the settlement curve of the live load of the train.Through the comparison of various factors influencing the settlement of the transition section,the simulation results show that the foundation settlement is always the main factor affecting the settlement of the road and bridge transition section.Gradually weakening,while increasing the elastic modulus of the foundation will reduce the uneven settlement of the transition section of the road and bridge;the material properties of the transition section have a certain effect on the uneven settlement;The effect of uniform settlement is minimal;as the slope increases,the settlement waveform becomes unstable,the settlement rate increases,and the amount of settlement at the abutment increases,which affects the size of the uneven settlement.