Multi-span Box Culvert Jacking Construction Risk Analysis And Monitoring Technology Research

In the construction of bridges under the existing railways,the jacking box culvert method is a major construction method.The application of the construction method in the project perfectly solved the construction problem of the intersection of the new line and the existing line,and changed the leveling to the interchange,thus achieving a wide range of applications.However,there is a certain risk in the construction process of the box culvert under the cable jacking.Therefore,necessary risk analysis and construction monitoring must be carried out during the construction process to ensure the smooth progress of the jacking construction.This paper combines the construction of a four-span jacking box culvert under the existing railway on a certain highway,and studies the risk monitoring and mechanical analysis during the jacking construction process of the box culvert.The main research contents are as follows:1.Survey and analysis of the project overview of the jacking bridge construction,analysis of the location of the project,engineering structure,engineering geological conditions,hydrologicalconditions,climatic characteristics and engineering characteristics,combined with the project overview,the box culvert The construction plan was discussed,It ensures the feasibility of the construction scheme of the box culvert.2.The safety performance of the deep foundation pit during the construction of the box culvert was checked.During the verification,the two types of working conditions were checked for the safety performance of the foundation pit near the railway side and the safety performance of the remaining three sides.For various working conditions,the settlement calculation of the surrounding pit,the bending moment and shearing force calculation of the supporting pile,the calculation of the overall stability of the foundation pit,the calculation of the foundation pit anti-overturning stability,the foundation pit anti-lifting check calculation and the protective pile embedding Solid depth calculation.The calculation results show that the settlement around the foundation pit and the remaining three sides of the foundation pit,the settlement of the foundation pit,the bending moment and shearing force of the supporting pile,the overall stability of the foundation pit,the anti-overturn stability of the foundation pit,and the antilifting performance of the foundation pit And the embedded depth of the protective piles meets the requirements of the specification,thus ensuring the safety performance of the deep foundation pit during the construction of the box culvert.3.The risk monitoring measures for deep foundation pits during the construction of box culvert are determined,including the content and method of monitoring,monitoring frequency and warning value,processing of monitoring data and information feedback,The effectiveness of monitoring during the construction of the box culvert is guaranteed.4.The structural mechanical properties of the box culvert prefabrication and jacking process were checked.The calculation includes the mechanical performance check of the bowland-buckle bracket during the prefabrication of the box culvert,the mechanical performance check of the girders and the piers for the railway reinforcement during the jacking process,and the jacking force and the back beam of the box culvert during the jacking process.The mechanical properties of the check.The calculation results show that the mechanical properties of the box girder prefabrication and jacking process meet the requirements of the specification.5.The research and analysis of the on-site test results of the box culvert during the construction process were carried out.The research contents mainly include the displacement results and analysis of the foundation pit pile top and the railway subgrade monitoring point during the construction process,the monitoring and analysis of the jacking force and offset during the jacking process of the box culvert,and the control measures during the jacking process of the box culvert.Through research and analysis,it can be seen that the displacement of the monitoring points during the construction process of the box culvert and the offset of the box culvert during the jacking process are small,meeting the requirements of the regulations,and the prefabrication and jacking construction of the box culvert has achieved a complete success.