Study On The Influence Of Self Shrinkage Of Concrete In The Compartment Of Double Steel Shell Self-compacting Concrete Immersed Tunnel

Double steel shell self compacting concrete immersed tunnel is composed of many relatively independent compartment structures.Compared with ordinary reinforced concrete immersed tunnel,it has many advantages,such as high strength,less water seepage,good ductility and so on.Its engineering application has been developed rapidly.However,the high content of self compacting concrete cementitious materials and the low water binder ratio lead to the water loss and self shrinkage.The self shrinkage of concrete is one of the reasons for the original cracks,which will have a negative impact on the durability of concrete structure,and also affect the mechanical properties of the interface between steel plate and self compacting concrete.Therefore,it is of great practical value to study the self shrinkage of self compacting concrete in the compartment model of double steel shell immersed tunnel.In this paper,based on the construction of double steel shell self-compacting concrete composite structure immersed tunnel in Shenzhen-Zhongshan channel in China,by consulting relevant documents and using ABAQUS finite element software,the compartment model of double steel shell self-compacting concrete immersed tunnel is established.The self shrinking volume strain of self-compacting concrete and its stress and displacement effect on concrete and steel members as well as the relative displacement of steel plate concrete interface are studied.The following conclusions are drawn:?1?When the parameters of self shrinkage volume strain and elastic modulus of C50 self-compacting concrete are missing in similar projects,the modified Zhao Sumei concrete self shrinkage model and American ACI specification model are proposed to predict respectively.?2?By establishing the model of plain concrete and steel plate concrete composite structure respectively,it is found that the calculated value of concrete autogenous shrinkage volume strain is consistent with the predicted value and theoretical value of the model,which proves that it is feasible to use ABAQUS finite element software to simulate the autogenous shrinkage of concrete in the compartment model of double steel shell self-compacting concrete immersed tunnel.?3?Combined with the displacement nephogram,tensile damage nephogram and maximum principal tensile stress nephogram of concrete restrained self shrinkage in the compartment model,it is comprehensively judged that the position of concrete contacting with T-shaped steel and transverse stiffener is cracked in tension on the 7th day after concrete pouring,which leads to local tensile damage of concrete.?4?The final value of restrained self shrinkage volume strain of concrete in compartment model is 166.2×10^-6is 44.77%less than that of plain concrete model and 39.47%less than that of steel plate concrete composite structure model.It can be seen that steel members such as steel plate,T-beam and transverse stiffener have a strong restraining effect on the self shrinkage of concrete.?5?In the compartment model,the displacement of the steel-concrete interface changes unevenly,and the maximum average separation displacement of the steel-concrete interface in Z direction is 0.119 mm,the maximum displacement of concrete model in the same direction is 0.172 mm,reduced 44.78%.This shows that the separation displacement of steel plate,T-beam and transverse stiffener greatly reduces.