洲头咀沉管隧道干坞抽水扰动下模袋砂围堰力学响应研究

Mechanical Response of Geotextile Bag with Sand Cofferdam under Pumping Disturbance of Zhoutouzui Immersed Tunnel

为深入研究模袋砂围堰对沉管隧道干坞抽水力学响应规律,以广州洲头咀沉管隧道模袋砂围堰工程为背景,建立干坞抽水全过程精细数值模型。计算验证了钢板桩+袋装黏土组合芯墙止水性能。分析了干坞抽水引起的模袋砂围堰变形规律。并揭示了围堰土工模袋张力分布规律,此外提出模袋张力简化计算方法。研究表明:模袋砂围堰钢板桩+袋装黏土组合防渗芯墙止水效果良好,能有效控制临江侧水流渗入干坞侧;干坞侧抽水对模袋砂围堰变形产生了显著的影响,变形与坞内下降水位近似呈同向线性关系;坞内水位降低使围堰重度由浮重度变为干重度,引起模袋砂压实而出现较大竖向位移;围堰竖向压缩和水头差引起的渗流作用又促使围堰的水平位移;模袋砂围堰中土工模袋受到的张力随着坞内抽水水位的降低近似线性增大。模袋张力简化法计算值与数值计算结果对比表明,模袋张力采用的简化计算方法具备合理性。

The detailed model for dry-dock pumping process was established based on Zhoutouzui immersed tunnel in Guangzhou to investigate mechanical response of geotextile bag with sand cofferdam. The performance of waterstop wall combined of steel sheet pile and bagged clay was evaluated and the deformation of geotextile bag with sand cofferdam was explored as well as the tension of geotextile bag was calculated,which simplified calculation method was proposed. The results show that the effect of combined waterstop wall is excellent. The influence of drydock pumping on cofferdam deformation is significant,which is a homodromous linear relation. The density of cofferdam increase caused by dewatering,which increases overlying pressure from upper geotextile bag to lower one and makes geotextile vertical flattening deformation. And then flattening deformation and seepage caused by head difference make cofferdam horizontal displacement. The tension of geotextile bag increases with water level decrease in a nearly linear relation and comparing with numerical calculation results indicate that simplified calculation method of tension is reasonable.