高水位环境下沉管隧道模袋砂围堰破坏模式研究

Study of Failure Pattern of Geotextile Bag with Sand Cofferdam of Immersed Tunnel in High Water Level Environment

为研究高水位环境下沉管隧道模袋砂围堰的破坏形态与破坏机制,依托广州市洲头咀沉管隧道,通过室内试验和理论分析,探讨高水位环境下沉管隧道高坡率模袋砂围堰失稳破坏形态,提出相应的破坏控制指标与评价方法,并通过数值计算验证。研究结果表明:1)硬质地基中,模袋砂围堰在竖向荷载作用下会出现边角处应力集中张拉破坏与砂袋界面处应变局部化破坏,水平荷载作用下表现为内部或整体滑动; 2)软弱地基中,由于地基承载力不足,会引起围堰局部脱离或底层模袋张拉破坏; 3)实际工程中,模袋砂围堰中的模袋难以被贯穿撕裂,无法形成围堰内部整体弧形滑动; 4)模袋砂围堰存在明显的包裹增强效应,能有效提高整体稳定性,高水位环境中模袋砂围堰设计坡率显著大于常规土石坝围堰设计坡率。

In order to study the failure modes and mechanism of geotextile bag with sand cofferdam of immersed tunnel in high water level environment,the failure modes of instability of high slope rate geotextile bag with sand cofferdam of Zhoutouzui Immersed Tunnel in high water level environment are discussed by laboratory experiment and theoretical analysis.The damage control indices and evaluation methods are proposed and verified by numerical calculation.The study results show that:(1)In hard foundation,the tensile failure of stress concentration and strain localization failure will occur at the corner and interface of geotextile bag with sand cofferdam respectively under vertical load;and the internal or integral sliding will occur to geotextile bag with sand cofferdam under lateral load.(2)In soft foundation,partial detachment or tension failure will occur to cofferdam and bottom geotextile bag respectively due to insufficient foundation bearing capacity.(3)In practice,the geotextile bag are hard to be perforated and cannot form the integral curved sliding inside the cofferdam.(4)The geotextile bag with sand cofferdam has obvious package enhancement effect,which can effectively improve the overall stability;and the design of slope rate of geotextile bag with sand cofferdam in high water level environment is significantly higher than that of conventional earth-rock dam cofferdam.