Research On Design And Calculation Method Of Masonry Arch Culvert Strengthened With Increasing Cross-section Method

The main canal of Red Flag Canal in the old city of Changsha city was built in the 1950s.Its body structure is mainly in the form of brick arch culvert,precast concrete circular arch,precast concrete cover culvert,situ concrete box culvert and mortar flag stone curb wall.While the main canal of Hongqi Canal is in overdue service,it is also faced with the reality that the urban drainage volume is increasing and the load of the canal is increasing.From 2015 to 2018,the main canal of Hongqi Canal collapsed at the Wuyi Road intersection of Shuguang Road,Xiaoyuan Park,and the dormitory area of the Provincial Water Conservancy Institute.It marks that the canal body has entered a period of frequent accidents,and the canal body structure has great potential safety hazards.Therefore,in order to ensure the travel safety of the surrounding residents and the effective operation of the Hongqi Canal drainage system,it is extremely urgent to repair and strengthen the existing pipe canal structure.Combined with the actual situation of the old city,this project adopts trenchless rehabilitation.Because there is no applicable design specification for the new and old composite structures formed by masonry arch culverts strengthened with increasing cross-section method,it is necessary to study it before large-scale repair and strengthened of the main canal of Red Flag Canal.Changsha University of Science&Technology and The Fifth Bureau Of China State Construction Engineering Corporation jointly established the project " Research and implementation of construction method of main canal structure strengthened test section of Hongqi Canal",this research is one of the sub-projects.Firstly,on the premise of analyzing a series of existing calculation methods of masonry arch culverts,basic assumptions and calculation diagrams are put forward,and then two calculation methods for internal force of pipe culverts considering passive earth pressure of soil are proposed.They are the spring-structure culvert internal force calculation method which simplifies soil as a constraint spring and soil-structure culvert internal force calculation method which considers soil-structure interaction respectively.The influence of elastic resistance coefficient of foundation on the calculation result of internal force ofspring-structure culvert and the influence of soil constitutive model on the calculation result of internal force of soil-structure culvert are analyzed.Secondly,this study compares and analyzes the calculation results of various internal force calculation methods by taking the reinforced arch culvert structure of the main canal structure strengthened test section of the Hongqi Canal in Changsha City as an example,and puts forward suggestions for selecting the calculation method of the shallow-buried masonry drainage main canal.Thirdly,by analyzing the force characteristics of the arch ring before and after strengthened,the basic assumptions are put forward by studying the failure characteristics of the masonry arch culvert,and then the calculation diagram is proposed and the calculation formula of the normal section bearing capacity of the single-sided composite brick masonry arch culvert is deduced.The theoretical value is compared with the experimental value,and it is found that the theoretical value and the experimental value are in good agreement.Finally,the calculation method of the internal force of the spring-structure pipe culvert and the calculation formula of the section bearing capacity of the reinforced masonry arch culvert proposed in this paper are applied to the engineering design of the main canal structure strengthened test section of the Hongqi Canal in Changsha City.