Research On Temperature Stress And Crack Prevention Of Side Wall Concrete In Subway Station

With the rapid development of subway construction in China,subway has become one of the main modes of transportation for urban residents.As a place for passengers to wait and transfer,subway station is the most important part of the subway system,however,the frequent leakage of the subway station seriously affects the durability and safety of the station structure,especially the leakage caused by the early cracking of the side wall of the subway station,which brings many difficulties to the later repair and maintenance.The temperature stress caused by the hydration heat of mass concrete is the key reason for the cracking of the side wall of the subway station.Therefore,it is of great theoretical research and engineering application value to master the change process and distribution law of the temperature stress of the side wall concrete of the subway station to prevent the concrete crack leakage of the side wall of the station.Based on the whole construction process of the main structure of Xizhou Station of Zhengzhou Rail Line 12,the cracking situation and causes of the side wall are analyzed and studied.Then,the ABAQUS finite element software is used to simulate the temperature field and stress field of concrete.The development process over time,and the effects of different mold temperatures of concrete,sudden drop of external temperature and different formwork support methods on temperature stress are discussed.Finally,based on the numerical simulation results and field plugging tests,the prevention and control measures of side wall cracks in subway stations are proposed.The main research contents of this paper are as follows :(1)The problem of water leakage in subway stations dominated by Xizhou station is investigated,and the characteristics and causes of side wall cracking are studied and analyzed,the influence of temperature and constraint on station cracking is found;(2)Based on the user subroutine of ABAQUS,the secondary development is carried out.The subroutine is written in FORTRAN language.The hydration heat release process of subway station concrete is simulated by HETVAL.The difference of ambient temperature and convective heat transfer coefficient is reflected by FILM,and the change of concrete elastic modulus with time is reflected by USDFLD;(3)By establishing the finite element model of the subway station side wall,the temperature field and stress field of the subway station side wall are analyzed.The variation trend of the center temperature,the temperature difference between the inside and outside,and the maximum tensile stress of the side wall concrete are studied.The different mold temperature of the concrete,the sudden drop of the external temperature and the different formwork support methods are simulated,and the variation law of the temperature stress is obtained.At the same time,the risk of side wall cracking is analyzed,and the advantages and disadvantages of the steel formwork and wood formwork support methods are compared;(4)From the research of cement,aggregate,admixture and admixture,the measures to reduce the hydration heat and shrinkage of concrete are put forward.According to the site construction,the pouring process and maintenance control scheme are optimized.At the end of the paper,a new material polyurea grouting slurry is used to plug the 9 leakage water of the side wall,which provides a reference value for the subway project.