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为了准确评价泥水盾构存在反向水压条件下开挖面形成泥膜的致密程度,利用自制的可施加反压的泥浆渗透装置,开展6组不同压力条件下的泥浆渗透试验,通过测试试验过程中的滤水量和地层孔压的变化,以及形成泥膜的厚度和含水量,计算泥膜渗透系数、干密度及有效泥浆压力转化率等指标,分析有、无反压条件下泥膜的致密程度差异及其形成机理。研究结果表明,反压的存在降低了有效泥浆压力转化率,使得形成的泥膜孔隙比和渗透系数更大,干密度更小,即泥膜结构更为疏松;采用滤水量与泥膜体积的比值较单独采用滤水量可以更准确地评价泥膜的致密程度,其比值越大表示单位体积的泥膜内含有的土颗粒越多,泥膜结构越致密。研究结果对实际工程中泥膜质量的评价及开挖面稳定性分析有重要意义。
In order to accurately evaluate the density of mud film formed on the excavation face under the condition of reverse water pressure in the mud shield, six sets of mud penetration tests under different pressure conditions were carried out by using self-made mud infiltration device capable of applying backpressure. Through the test The process of the amount of water and formation pore pressure changes, as well as the formation of mud membrane thickness and moisture content, calculation of mud permeability coefficient, dry density and effective pressure conversion rate of mud and other indicators, with or without pressure under the conditions of mud membrane Differences in Density and Formation Mechanism. The results show that the existence of backpressure reduces the effective pressure conversion rate of mud, making the muddy membrane porosity and permeability coefficient larger, dry density smaller, that is, the muddy membrane structure is more loose; using the amount of water and mud membrane volume Compared with the single filtrate, the density of mud membrane can be evaluated more accurately. The larger the ratio is, the more soil particles contained in the mud membrane per unit volume, the more dense the mud membrane structure. The research results are of great significance for the evaluation of mud quality and the analysis of the stability of the excavation face in practical engineering.