泥水平衡盾构施工对地层孔隙水压力的扰动规律研究

Ground Pore Water Pressure Disturbed by Slurry Balanced Shield Tunneling

为研究泥水平衡盾构施工对地层孔隙水压力的扰动规律,针对3种典型地层开展流固耦合分析,研究盾构施工期间不同阶段地层孔隙水压力的纵向和横向变化规律,提出孔隙水压力扰动比的概念并对其施工扰动的程度进行评价。研究结果表明:1)泥水平衡盾构在经过软土地层时,孔隙水压力会有明显的下降趋势;2)泥水平衡盾构掘进会对开挖面前方土体孔隙水压力产生不同程度的水力堆积效应,该堆积效应的产生是泥膜产生的必要条件之一;3)不同地层中泥水平衡盾构施工对孔隙水压力造成的扰动不同,拱顶位置孔隙水压力扰动最大,拱腰次之,拱底最小;4)施工中注浆压力的施加与孔隙水压力的扰动程度密切相关;不同地层在不同的开挖阶段横断面渗流场的分布规律和形状不同,拱顶处均表现为水流压力集中点;同时,泥水平衡盾构在施工期对孔隙水压力的扰动有残余效应。

In order to study the disturbance law of pore water pressure caused by slurry shield tunneling,based on the fluid-solid coupling analysis of three typical strata,the influence of vertical and lateral variation of pore water pressure in different stages of shield tunneling is studied.The concept of pore water pressure disturbance ratio is proposed and the degree of construction disturbance is evaluated.The study results show that:(1) The pore water pressure of slurry shield tunneling will decrease obviously when it passes through soft soil stratum.(2) The slurry shield tunneling will cause different degree of hydraulic accumulation effect on pore water pressure of soil in front of excavation face,which is one of the necessary conditions for the formation of filter cake and affects the disturbance of pore pressure during excavation.(3) During construction period,the disturbance of pore pressure caused by slurry balanced shield construction in different strata varies;the disturbance of pore water pressure at vault position is the largest,followed by that at arch waist,and that at arch bottom is the smallest.(4) The application of grouting pressure in construction is closely related to the disturbance degree of pore water pressure;the distribution and shape of cross-section seepage field in different strata at different excavation stages vary;the vault shows the concentration point of flow pressure;and meanwhile,the slurry shield tunneling has residual effect on pore water pressure disturbance during construction period.