超大型陆上沉井下沉施工自动化监控技术及结构应力分析

Automatic monitoring technology and structural stress analysis of super large onshore caisson during sinking

在超大型陆上沉井下沉过程中,由于井壁土压力、端部阻力、沉井内水位以及沉井姿态的变化,沉井结构应力将会发生显著变化。依托南京龙潭长江大桥南锚碇陆上沉井工程,基于全自动化沉井监测数据,进行结构应力分析研究,结果表明:自动化监控系统能够实时高效地获取沉井关键数据,监控结果反应出不同施工阶段结构的受力及变位特征;沉井底部竖向土压力四角位置显著大于其余位置,说明四角存在明显应力集中现象;井壁水平土压力监测最下端应力小于中下部,验证了刃脚周边应力扰动区的存在;隔墙底部钢壳混凝土是沉井结构最薄弱的位置,在钢壳混凝土浇筑至第2次下沉完成阶段,结构安全风险较高。若在接高过程中出现拉裂风险,可将每次对角浇筑分多次开展,以充分利用结构自身抗力减轻拉应力发展。研究结论对类似工程的设计和施工具有一定借鉴价值。

During the sinking process of super large onshore caisson,the structural stress of caisson will change significantly due to the changes of earth pressure,end resistance,water level in caisson and attitude of caisson.Based on the south anchoring onshore caisson project of Nanjing Longtan Yangtze River Bridge,the structural stress analyses were carried out based on the automated caisson monitoring data.The results show that the automated monitoring system can acquire the key data of caisson in real time and efficiently,and the monitoring results reflect the structural stress and displacement characteristics in different construction stages.The vertical earth pressure at the bottom four corners of the caisson is significantly greater than the other positions,indicating that there is an obvious stress concentration phenomenon at the four corners.The stress at the bottom of the horizontal earth pressure monitoring is smaller than that at the middle and bottom of caisson,which verifies the existence of stress disturbance area around the cutting.Steel shell concrete at the bottom of partition wall is the weakest position of caisson structure,and the structural safety risk is higher from the first casting to the second sinking.If the risk of tensile cracking occurs in the process of casting,each diagonal can be carried out several times to make full use of the structure's own resistance to reduce the development of tensile stress.The conclusion can be used for reference in the design and construction of similar projects.