预制沉管隧道早期裂缝控制因素敏感性分析

Sensitivity Analysis of Influence Factors in Early-age Cracking Control of Prefabricated Immersed Tunnel

沉管隧道预制过程中的早期裂缝控制一直是工程关注重点之一。基于工厂化预制施工流程,模拟分析了沉管节段早龄期性能的发展过程;进而引入开裂风险系数,运用敏感性分析方法分析了沉管隧道预制过程中带模养护、室内养护和室外养护三个不同阶段中入模温度、模板形式、室内室外养护温度等因素对沉管节段早期裂缝控制的影响。分析结果表明,入模温度、室内养护温度、材料配比对开裂风险系数的影响最为显著,模板形式次之,拆模时间在一定范围内对开裂风险系数有影响,室外养护条件则影响较小。在工厂化预制过程中应在材料制备阶段对材料配比,带模养护阶段对入模温度和室内养护温度进行科学控制。

Control of early-age cracking during the fabrication process of immersed tunnel is one of the key is- sues to ensure the designed service-life requirement. In this paper, the coefficient of cracking risk and sensitivity a- nalysis method are respectively introduced to describe the evolvement of early-age performance of segments during the fabrication process of immersed tunnel, which is divided into three phases： the phase of curing with formwork, the phase of indoor curing and the phase of outdoor curing. Crack control factors at early age including fresh concrete temperature, formwork removal time, the kind of formwork, concrete mixture ratio, indoor curing temperature and outdoor curing temperature are discussed. The results show that the concrete mixture ratio, fresh concrete temperature and indoor curing temperature are the most significant factors, and the posterior one is the kind of formwork. The formwork removal time has influence on coefficient of cracking risk in certain scope, but the outdoor curing condition has little influence. Thus, the concrete mixture ratio, fresh concrete temperature and indoor curing temperature need to be strictly and reasonably controlled in the phase of material preparation and the phase of curing with formwork re- spectively.