Simulation Analysis On Temperature Field And Stress Field Of Mass Concrete Tube Tunnel Hydration Heat

With the development of building materials and construction technology,mass concrete is widely used in civil engineering industry.However,because of its large volume,cross section,and the difference of internal temperature and external temperature,mass concrete structure may crack and cause safety problem.Therefore,control the temperature of mass concrete structure is an important issue in construction.It is well known that the cracks of mass concrete structure cracks is caused by temperature stress,which not only relates to temperature difference,but also relates to other factors,such as constraint conditions.In order to study the temperature field and stress field of mass concrete hydration heat,the main following aspects are carried out in this paper:(1)Based on hydration heat theory of mass concrete and the redevelop technology of ABAQUS software,compiling HETVAL,FILM and USDFLD software user subroutines by FORTRAN,which simulates time-varying heat transfer of concrete,time-varying curing temperature and time-varying elastic modulus of concrete,respectively.The validity of the user subroutines are verified by analyzing an 1m side length concrete cube and the immersed tube of the Hong Kong Zhuhai Macao Bridge which casting amount is 3420m3 a single.And compare the difference of the analysis result between sequentially coupled thermal-stress analysis and fully coupled thermal-stress analysis.(2)Simulates the 56 d casting period temperature field and stress field of one immersed tube tunnel of summer,spring & autumn,and winter,which one-time casting concrete volume is 4837m3,with 30? casting temperature and changing curing temperature,by using ABAQUS software,user subroutines and the method of sequentially coupled thermal-stress analysis.The results show that in summer time,the temperature differences of the immersed tube tunnel match Code GB 50496-2009.While the first 19 min of curing concrete,compressive stress is larger than compressive strength.And the tensile stress is greater than tensile strength from 30 h to 245 h.However,the difference of interior temperature and exterior temperature is greater than 25? in spring & autumn and winter.And the impact time of compressive stress and tensile stress are longer than those in summer.It means that,casting temperature and curing temperature should not differ too much.(3)Study the influence of casting method,dismantling template time,curing temperature and concrete casting temperature,on the temperature field and stress field of immersed tube of summer by the method of parameter analysis.The results show that casting concrete layer by layer is useless to reduce the peak temperature and stress.Shorting the dismantling template time affects little to the temperature field and stress field of the immersed tube,but can reduce temperature difference.Higher curing temperature can lead a higher peak temperature and lower temperature difference,if casting temperature is similar to curing temperature.But it can't prevent cracks from happening.When concrete casting temperature is lower than curing temperature,it is easy to produce tensile cracks in late stage of the maintenance period.When concrete casting temperature is closed to curing temperature,the higher casting temperature leads to higher peak temperature and higher temperature difference and can reduce the total time that compressive stress larger than compressive strength.If concrete casting temperature is similar with curing temperature,it can reduce the total time that tensile stress larger than tensile strength.