Research On Integrated Crack Prevention Technology Of Single-Sided Prefabricated Composite Wallboard In Precast Monolithic Underground Station

The emergence of precast monolithic underground station is in line with the development trend of modern building assembly industrialization,which can not only meet the needs of green development,but also improve the scientific and technological content of urban rail.After the technology matured,it can more effectively ensure the quality of the project,save resources and reduce costs.In the future of underground station construction,the prefabricated technology has a broad space for development and utilization,and the prefabricated composite wallboard is undoubtedly a kind of industrial construction product as the times require.In this project,single-sided prefabricated composite wallboard will be used in the side wall of underground station structure,which is the first application.In order to ensure the impermeability and durability of reinforced concrete in underground structure,it is necessary to strictly require the quality of the interface of new and old concrete in single-sided prefabricated composite wallboard.This is because when the shrinkage of old concrete is completed,the shrinkage of new concrete is just beginning,so cracks are easy to form at the interface.Therefore,it is very important to carry out the research on the mechanical performance of the interface of the composite wallboard to improve the anti cracking performance of the wallboard.Based on the crack prevention requirements of the side wall of precast monolithic underground station,combined with the characteristics of single-sided prefabricated composite wallboard,this paper takes the interface between precast and cast-in-place concrete as the research object,and carries out the mechanical performance test of the interface and the overall mechanical performance test of single-sided prefabricated composite wallboard.According to the test results,the comprehensive crack prevention technology of single-sided prefabricated composite wallboard of the side wall of precast monolithic underground station is extracted,which can provide reference for the same type of engineering.The main research contents and conclusions are as follows.(1)The test with two different construction techniques of interface,namely,exposed aggregate construction technology and chiseling construction technology,are made for the shear and split tensile tests.According to the comparison of the test results,it is found that the interface based on tension is more suitable for water exposed aggregate construction technology,and the interface based on shear is more suitable for chiseling construction technology.(2)Using the optimized construction technology of interface,the single-sided prefabricated composite wallboard was made,and the bending and bias tests are carried out.By comparing with the test results of integral cast-in-place components,it is found that,the phenomenon of composite wallboard and cast-in-place wallboard in the bending test is similar,and both of them develop trapezoidal cracks.In the bias test,the compressive cracks of the composite wallboard are more than tensile cracks,and the failure occurs at the top of the side under eccentric loading,while the tensile cracks of the cast-in-place wallboard are more than compressive cracks,and the failure occurs in the middle of the side under eccentric loading.(3)According to the phenomenon of bending and bias tests,by adjusting material behavior parameters and interaction property parameters of new and old concrete interface,the finite element model is established,which is consistent with the experimental results.Simulating the stress state of prefabricated components under various working conditions,including moving,lifting,installing,overturning,demoulding and stacking.Based on the results,the most unfavorable stress state is moving and lifting.(4)Using the elastic stress reinforcement method,combined with the finite element model analysis,recheck whether the reinforcement of prefabricated structure is safe.The actual reinforcement is greater than the stress reinforcement,determined to be safe,to meet the requirements of finite element stress reinforcement calculation.(5)This paper summarizes and puts forward the integral anti crack construction technology of single-sided prefabricated composite wallboard,including the formulation of concrete anti crack technical scheme,the optimization of interface anti crack construction technology and the formulation of anti crack construction measures under various working conditions.