基于离心模型试验的水下保护沉箱沉降规律研究

Study on settlement law of underwater protective caissons based on centrifugal model tests

水下保护沉箱可以有效防护水下生产系统免受船锚和渔网拖曳、海底滑坡冲击以及冰山撞击等风险,但沉箱一旦发生超出允许变形量的沉降,将会引起沉箱内采油树失稳,管汇及沉箱跨接管、海管、脐带缆等发生断裂,进而酿成油气泄露等重大工程事故。通过开展离心模型试验研究了水下保护沉箱基础在基坑开挖安装就位和自重固结过程中的沉降规律,并采用Weibull曲线模型拟合出最终沉降量的预测公式。离心模型试验预测的最终沉降量与数值模拟、规范理论计算结果的对比,发现三种方法的预测沉降量较为接近。通过分析离心模型试验结果可知:基坑开挖完成后,基坑底部出现较为明显的回弹变形;在沉箱基础安装后的固结过程中,基础底部土体的回弹量有所减小,但回弹变形依旧存在。

Underwater protective caissons can effectively protect subsea production systems from risks,such as the dragging of the ship anchors and fishing nets,the impact of the submarine landslides and iceberg.However,if the settlement of the caisson exceeds the allowable value,the instability of the Christmas tree in the caisson,and the fracture of the manifold,caisson crossover,subsea pipe and umbilical cable will occur,leading to major engineering accidents(i.e.oil and gas leakage).Centrifugal model tests were performed to study the settlement law of the underwater protective caisson in the process of the foundation installation and self-weight consolidation.The Weibull Curve was used to fit the prediction formula of the final settlement.The final settlement predicted by the centrifugal model tests was compared with the results obtained from the numerical simulation and standard theoretical calculation.It can be found that the settlement values predicted by the three methods are close.The centrifugal model test results show that obvious rebound deformation is observed at the bottom of the foundation pit after the foundation pit excavation.During the consolidation process after the caisson installation,the rebound value of the soil at the bottom of the foundation is decreased,but the rebound deformation still exists.