Full-scale Static Tests And Seismic Behaviours Study Of Prefabricated Underground Utility Tunnels

In recent years,China has made significant progress in advancing municipal infrastructure construction.The construction of urban underground utility tunnels and construction industrialization has been included as important strategic measures in the "14th Five-Year Plan" for the construction industry.In this context,this paper proposes a new type of prefabricated assembly integral underground utility tunnel structure.Through the analysis of internal forces of cast-in-situ utility tunnel structures,division of prefabricated components,design of assembly structures,manufacturing of prefabricated components,and construction and hoisting,the construction of a full-scale model of prefabricated assembly integral utility tunnel was completed.The static and dynamic mechanical properties of the prefabricated assembly integral underground utility tunnel were studied using theoretical research,full-scale model static load tests,and numerical simulation methods,and compared with traditional cast-in-situ methods.The main research contents are as follows:(1)A new type of prefabricated assembly integral utility tunnel structure is proposed.Assembly joint connection forms such as mortise and tenon joints,bull leg joints,and prefabricated composite slabs are selected.The failure mechanism of joint connections is studied,and a mechanical model of the cracking bending moment and ultimate bending moment of mortise and tenon joints is established.Taking a planned utility tunnel project in Qianhai,Shenzhen as the background,through the analysis of internal forces of cast-in-situ structures,the division of prefabricated assembly utility tunnel components,the design of the whole and components,and waterproof measures were proposed.The entire process of model production and installation rehearsal was completed,and the manufacturing of assembly utility tunnel components and the hoisting and forming of full-scale models were completed.(2)Static load tests on the full-scale model of the prefabricated assembly integral utility tunnel were carried out.The test used a through-core jack to tension the steel strands and apply monotonic static loads to the utility tunnel structure to obtain the load-displacement curve of the utility tunnel structure under different conditions,the stress-strain state of the steel bars and concrete,and the crack extension at the mortise and tenon joints.The test results show that the deformation of the prefabricated assembly composite top plate is relatively small,the maximum deflection at the center of the large warehouse is 1.465 mm,and the maximum displacement of the mortise and tenon joints reaches 2.82 mm.During the loading process,slight grouting bursts were found at the mortise and tenon joints.The test results show that the prefabricated assembly utility tunnel structure exhibits excellent bearing performance as a whole,the mortise and tenon joint connection method is proved feasible,and the bearing capacity of the overall structure can meet the requirements of practical engineering applications.(3)Established finite element numerical models of prefabricated assembly integral and cast-in-situ utility tunnels in double-chamber and triple-chamber forms.The experimental and simulated results of the double-chamber full-scale model were compared and analyzed,and the results show that the displacement and strain results obtained from the experiment and simulation are in good agreement,verifying the accuracy and reliability of the model construction.The numerical study results reveal that the assembly and cast-in-situ utility tunnels in double-chamber and triple-chamber forms exhibit similar deformation and stress development trends in terms of deflection and stress.(4)Revealed the seismic performance of the prefabricated assembly integral utility tunnel structure.The internal force distribution of the assembly utility tunnel structure and the cast-inplace structure under earthquake conditions was studied and compared.By analyzing the mechanical performance of the mortise and tenon joints of the assembly utility tunnel under increasing peak ground acceleration of the earthquake,based on the mechanical model of the cracking bending moment and ultimate bending moment of the joint,the limit value of interlayer displacement angle for the elastic-plastic layer of the prefabricated assembly underground utility tunnel structure was given.