襄阳东西轴线项目沉管预制局部块体试验研究

襄阳市东西轴线项目沉管预制采用节段整体式全断面顺浇法,具有高强度、大断面、大体积的特点,管节控裂难度较大。为验证混凝土配合比、施工工艺以及裂缝控制措施的可行性及可靠性,采用Midas FEA软件,进行沉管管节在设计工况下的水化热温度应力数值仿真模拟计算,分析管节浇筑过程中混凝土内部温度及应力变化情况。数值仿真结果表明,管节连接处抗裂安全系数较低。进而选取理论开裂风险最高的边墙倒角位置和施工难度最高的中隔墙倒角位置进行模型试验,实际模拟钢筋及预埋件施工工序,全面检验原材料、配合比和混凝土施工性能的可靠性,并布设智能温度监测系统。通过局部块体试验,合理优化钢筋及预埋件的结构形式和安装工序,验证混凝土性能并优选施工配合比;同时,通过提出的原材料温控标准对模型试验进行温度智能监测数据分析。

Experimental Study on Prefabricated Partial Block ofImmersed Tunnel ofXiangyangEast-West Axis Project

The immersed tunnel segments of East WestAxis Project in Xiangyang are prefabricated by integral full section down pouring method, which is characterized by highstrength, large cross section and large volume, and thesegment crack is difficult to control. In order to verify the feasibility andreliability of concrete mixing proportion, construction technology and crackcontrol measures, the finite element software Midas FEA is used to conductnumerical simulation and calculation on hydration heat temperature stress ofimmersed tunnel joints under design conditions, and the internal temperatureand stress variation of concrete during the casting of immersed tunnel segmentare analyzed. The numerical simulation results show that the anti cracking safety factor at the joint is low. Therefore, thechamfering position of the sidewall with the highest theoretical cracking riskand that of the middle separation wall with the highest construction difficultyare selected for model test. In the model test, the construction process ofreinforced bars and embedded parts is simulated, the reliability of rawmaterials, mixing proportion, concrete construction performance, etc. arecomprehensively checked, and an intelligent temperature monitoring system isset up. Through the partial block test, the structural types and installationprocedures of reinforced bars and embedded parts are rationally optimized, soas to validate the concrete performance and optimize the construction mixingproportion. Meanwhile, the raw material temperature control standards areproposed to analyze the monitoring data for model testing.