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目的:泥水盾构掘进时通过加压泥浆维持开挖面稳定,泥浆中的小颗粒渗入土体,大颗粒在土体表面堆积形成泥膜。本文研究泥浆的渗透行为和泥膜的渗透系数,提高对泥水盾构维持开挖面稳定机理的认识。方法:1.通过渗透柱试验模拟泥浆在砂土中的渗透;2.通过土体电导率的测定和电镜扫描,观测泥浆在渗透距离内的分布情况;3.假设泥膜厚度不变,通过孔压和渗流量观测泥膜渗透系数随时间的变化情况。结论:1.在泥浆的渗透距离内,泥浆含量沿着渗透方向以对数形式降低,大部分泥浆的细小颗粒集中在约100–300 mm的区域内,这个区域的大小与泥浆压力成正比;2.低渗透性泥膜形成时间约5 mim,泥水盾构掘进过程中,开挖面上来不及形成不透水泥膜。
OBJECTIVE: Slurry shield tunneling maintains a stable excavation surface with pressurized mud and small particles in the mud infiltrate into the soil. Large particles accumulate on the surface of the soil to form a mud film. In this paper, the permeability of mud and the permeability coefficient of mud membrane are studied to improve the understanding of the mechanism of maintaining shield tunneling stability. Methods: 1. Through the permeation column test to simulate the penetration of mud in the sand; 2. Through the measurement of soil conductivity and electron microscopy, to observe the distribution of the mud within the penetration distance; 3. Assuming the same thickness of mud, through Pore pressure and seepage flux observed mud membrane permeability with time changes. Conclusions: 1. The mud content decreases logarithmically along the infiltration direction within the mud penetration distance. Most of the mud particles are concentrated in the region of about 100-300 mm. The size of this region is proportional to the mud pressure. 2. Low-permeability mud film formation time of about 5 mim, mud shield tunneling process, the excavation surface time to form impervious mud.