盾构井内衬墙薄壁混凝土施工仿真和温控防裂研究

Research on Construction Simulation,Temperature Control and Cracking Prevention of Thin-wall Concrete Lining Wall in Shield Shaft

盾构井是珠江三角洲水资源配置工程重要组成部分,对盾构井内衬墙进行温度控制,防止裂缝产生是保证供水安全有效的必要措施。选取珠江三角洲水资源配置工程中B4标GS10号典型盾构井内衬墙结构,运用三维有限元仿真分析方法,采用逆作法施工顺序,考虑内衬墙和连续墙之间3种不同的连接方式(完全粘接、无粘接和弱粘接)下,研究浇筑温度、通水冷却措施下温度、应力发展变化规律和开裂风险。结果表明:无温控措施时内衬墙拉应力超过其抗拉强度,存在开裂风险,在通水冷却等措施下温度和应力降幅分别为10.34%和9.90%;对于1.5 m厚内衬墙,浇筑温度每提高1℃,最高温度升高0.69℃,应力增大0.12 MPa;水管加密、通水时间延长和降低通水水温均能有效降低内衬墙温度应力、减小结构开裂风险;内衬墙和连续墙粘接强度越大,对内衬墙混凝土的约束越大,开裂风险越高。

The shield shaft is an important part of the water resources allocation project in Pearl River Delta.The temperature control of the lining wall of shield shaft to prevent cracking is a necessary and effective measure to ensure the safety of water supply.Selecting the typical lining wall structure of GS10 shield shaft in B4 bidding contract as research object,the three-dimensional finite element simulation analysis method is used to study the change laws of temperature and stress development and the cracking risk under the pouring temperature and water cooling measures by considering the adoption of reverse construction sequence and three different connection modes(complete bonding,no bonding and weak bonding)between the lining wall and the continuous wall.The results show that:(a)without temperature control measures,the tensile stress of lining wall exceeds its tensile strength,so there is a risk of cracking,and under water cooling and other measures,the temperature and stress drop are 10.34%and 9.90%respectively;(b)for the 1.5m-thick lining wall,when the pouring temperature is increased by 1℃each time,the maximum temperature increases by 0.69℃and the stress increases by 0.12 MPa;(c)the increase of water pipe densification,the extension of water supply time and the reduction of water temperature can effectively reduce the temperature stress of lining wall and the risk of structural cracking;and(d)the greater the bonding strength between the lining wall and the continuous wall,the greater the constraint on the concrete of lining wall and the higher the risk of cracking.