施工养护措施对沉管隧道早期温度和应力影响的仿真分析

Simulation Analysis of the Influences of Construction and Curing Measures on the Early Temperature and Stress of an Immersed Tunnel

管段预制中所采用的施工养护措施是控制隧道早期温度裂缝的关键因素。文章基于舟山沈家门海底沉管隧道工程,采用MIDAS FEA软件数值分析了整体浇注和分层浇注、挂帘养护和蓄水养护措施对管段预制时温度场和应力场的影响规律,并与实测值进行了对比。研究结果表明：管段预制时底板的水化温度最高,在浇注1~2 d内水化温度达到峰值;底板与侧墙交界面腋角处温度应力最大,数值接近甚至有可能超过当龄期抗拉强度,是极易开裂的部位。施工中采用分层浇筑可以加快管段内部的热量散失,挂帘养护可以降低管段的内外温差,这两种措施都可以有效地降低混凝土沉管隧道管段早期温度应力和开裂的风险。蓄水养护不宜在施工初期采用,否则会在管段内形成较大的温度差。

Considering that construction and curing measures adopted in element prefabrication are the key factorsfor controlling early temperature cracking of an immersed tunnel, and using the construction of the Shengjiamen im-mersed tunnel in Zhoushan as an example, this paper analyzes the influences of integral casting, layered casting,curtain curing and water storage curing on the temperature field and stress field of elements during prefabricationbased on MIDAS FEA software. The obtained results are compared with the measured ones, showing that： 1） themaximum hydration temperature occurs at the tunnel floor during element prefabrication, with its peak value occur-ring within 1 or 2 days after casting; 2） the maximum temperature stress occurs at the haunch of the interface be-tween the floor and sidewall, with the value being close to or even greater than the current age tensile strength,which easily causes cracking; 3） layered casting can accelerate heat loss inside the element and curtain curing canreduce the differences of temperature inside and outside of the element, all of which can be used to effectively re-duce early temperature stress and cracking risk to the element; 4） water storage curing may cause great temperaturedifferences and is not suitable for the early stage of construction.