Temporary Reinforcement System And Safety Evaluation Method For Lines Crossing High-speed Railroad Projects

With the continuous development of China’s urban traffic,the phenomenon of crossover between urban roads and existing operating railroad lines is inevitable.When box culvert underpassing existing railroad construction method is adopted for public-railway crossings,it is a matter of concern to ensure that the underpassing project is carried out safely,smoothly and reliably without interrupting the continuous operation of existing railroad lines.Based on this,this paper takes the Liuzhou Hang Er Road Extension Line Underpassing Liunan Passenger Special Project as the background and adopts a research method combining theoretical research,field monitoring and numerical simulation to study the temporary reinforcement system and safety method of the box culvert underpassing high-speed railroad project line.The main contents of the study are as follows.(1)Studied the existing box culvert under the railroad project line temporary reinforcement general method,and analysis of the mechanism of the railroad line overhead reinforcement,combined with the technical key of the Liunan Passenger Dedicated under the project,proposed a pre-stressed reinforced concrete cross lift beam combined with D-type convenient beam of the railroad line temporary reinforcement method,the reinforcement method to ensure the safe and continuous operation of trains at the same time,can minimize the procedure of business line construction This reinforcement method can ensure the safe and continuous operation of trains while minimizing the construction procedures on the business line,thus improving the construction progress.(2)Based on intelligent monitoring technology,the monitoring method of temporary reinforcement system of Liunan Passenger Line was designed by using static level instrument,automatic measuring robot,strain sensor,highdefinition camera system and wireless signal receiver,etc.While the monitoring data were collected in real time,the construction site screen could be displayed in high definition.According to the relevant technical specifications and practical experience on site,the monitoring data are managed at three levels:control value,warning value and alarm value.The monitoring results show that the deformation and force of the temporary reinforced structure of the railroad line are within the control warning value,which indicates that the temporary reinforced system is safe and reliable.(3)The mechanism of dynamic train load generation is studied,and the dynamic train load is simulated by the artificial excitation fitting function method considering the vehicle speed,vehicle vibration characteristics,road conditions and line smoothness,and the time course curve of dynamic train load is drawn by Matlab software.Midas/GTS finite element software is used to calculate the deformation characteristics and stresses of the line temporary reinforcement system under different load conditions,and the results show that when the train speed is between 45 km/h-60 km/h,the line temporary reinforcement structure is more sensitive to the vibration effect of the train dynamic load,taking into account other uncontrollable effects under actual driving conditions,in order to ensure the safety of train operation.It is recommended that the train speed through the temporary reinforcement area of the line be controlled at 45 km/h.(4)In view of the force characteristics and deformation characteristics of the line temporary reinforcement system,a comprehensive safety evaluation index system of the line temporary reinforcement system is established,and the concept of comprehensive safety degree based on structural safety reserve is proposed.The weights of the safety evaluation indexes are determined by the method of linear combination of the comprehensive assignment of weights based on the hierarchical analysis method(AHP)and the mean square difference method(MSE),and a comprehensive safety evaluation model of the line temporary reinforcement system is established.Finally,under the speed limit of45 km/h,the comprehensive safety degree of temporary reinforcement system of Liunan special passenger line is 2.9 > 1,which indicates that the line reinforcement system is structurally safe and has a high safety reserve.