Research On Self-compacting Concrete Pouring Technology In Double Steel Shell Concrete Immersed Tunnel

With the development of the urban agglomeration in the Pearl River Delta,the national strategy for the construction of the Great Bay Area in Guangdong,Hong Kong and Macao is steadily advancing,and the economic development is increasingly dependent on transportation.The Pearl River Delta region is densely populated with rivers and some areas are close to bays.Bridges and tunnels are the main means to connect these areas.The solution of immersed tube tunnel is more and more coming into the view of engineering.Considering the geological and navigable requirements of the Pearl River Delta region,the immersed tube tunnel with double steel shell-self-compacting concrete composite structure can meet the performance requirements of high water pressure,high durability and large cross-section.However,the application of double-steel-shell-self-compacting concrete immersed tunnels is rare at home and abroad,and the construction of self-compacting concrete is still under exploration.Therefore,it is of great significance to study the construction of self-compacting concrete to solve practical engineering problems.This paper firstly carried out the investigation and analysis of the corresponding topics,and read the related literatures at home and abroad.Then combined with the theoretical analysis and the use of ANSYS FLUENT finite element software to study the influence factors of the concrete pouring of a immersed tube tunnel compartment in the double-steel casing-self-compacting concrete composite structure.Twelve finite element models are established to analyze the factors affecting the pouring quality of self-compacting concrete.The research results show that:（1）The simulation results of the new self-compacting concrete L-box test and the results of the literature simulation and the literature test results are well fitted.It is feasible to use the t₀ a and b parameters to characterize the new SCC for numerical simulation.（2）The use of t₀,a,b parameters to characterize the new SCC simulation double steel shell-self-compacting concrete composite structure casting process found that the larger the pouring port,the higher the casting speed,the shorter the time for the self-compacting concrete to fill the lower part,but the pouring quality is not ideal.（3）In order to obtain the best filling effect of the self-compacting concrete in the double-layer steel shell,the pouring speed,the pouring port diameter and the pouring mouth height should be controlled within a reasonable range during the pouring construction.The pouring speed should not be too large,otherwise the self-compacting concrete will be isolated due to the impact of the bottom steel plate splashing;the diameter of the pouring port should not be too large,otherwise the bottom filling quality is difficult to be guaranteed;the height of the pouring port should be kept at a low position as much as possible,and the pouring port is too high.In the process of self-compacting concrete falling,it may be isolated,and the second self-compacting concrete filling effect is not good.In the case of 12 sets of numerical simulations,the recommended casting speed is 2.0m/s,the pouring port diameter is 0.15m,and the pouring port height is 0.5m.（4）Based on the pouring experience related to the double steel shell-self-compacting concrete composite structure built or under construction at home and abroad,combined with the calculation results of the numerical simulation software Fluent,suggestions for the construction of self-compacting concrete.