泥水盾构泥膜形成时开挖面地层孔压变化规律研究

为保证开挖面的稳定，泥水盾构泥水舱中的泥浆必须在开挖面上形成微透水的泥膜，将部分泥浆压力转化为有效应力，泥浆压力才能平衡地层中的土压力和水压力。目前关于泥膜形成时泥浆压力的转化规律及其影响因素尚不清楚。针对这一问题，在自制的泥浆渗透装置中，以12组不同性质的泥浆开展渗透试验，通过测定泥膜形成过程中地层超静孔隙水应力的变化，并分析影响其分布的因素，明确了泥膜的作用机理。结果表明：随着泥膜的形成，泥浆压力在地层中转化为抵抗地层静水压力的孔压、超静孔隙水应力和抵抗地层土压力的有效应力；超静孔隙水应力在泥膜段迅速降低，在地层深处逐渐趋于稳定；泥浆的密度是影响地层超静孔隙水压力分布规律的主要因素之一，泥浆黏度对其影响较小。这一结果对于泥浆压力的设定和泥浆的配制有重要的指导意义。

Change of pore water pressure in soil as filter cakes formed on excavation face in slurry shield

To ensure the stability of excavation face in slurry shield, a filter cake with low permeability must be formed on the working face. Based on the filter cake, part of the slurry pressure can transform into effective stress. Then the slurry pressure can counteract the soil pressure and water pressure in the soil. The variation of slurry pressure as forming a filter cake and its influencing factors are still unknown at present. With regard to the problem, a slurry infiltration apparatus is developed and a series of pressure filtration tests are carried out on 12 different slurries. By measuring the change of the excess pore water pressure as forming a filter cake and analyzing its influencing factors, the working mechanism of the filter cake is identified. The test results indicate that the slurry pressure is transformed into three different parts: pore pressure to counteract the water pressure, excess pore water pressure, and effective pressure to counteract the soil pressure. The excess pore water pressure rapidly decreases in the filter cake, then reaches a steady value in the deep zone of soil. The density of slurries is one of the primary factors that influence the distribution of the excess pore water pressure, while the viscosity has little effect on it. This study has an important directive significance for setting slurry pressure and adjusting slurry in slurry shield.