A large amount of high-moisture-content muck will be generated during shield tunneling in sand-pebble-mudstone composite strata. Such muck not only leads to high transportation costs and poses environmental pollution risks in transit, but also easily triggers secondary disasters such as landslides if directly stockpiled. Therefore, it is essential to carry out dewatering treatment on shield muck prior to off-site transportation. Based on the shield tunnel intervals of Phase Ⅰ of Chengdu Metro Line 30, this study takes high-moisture-content shield muck from sand-pebble-mudstone composite strata as the research object. A vacuum electroosmotic drainage test apparatus was designed, and multi-condition orthogonal model tests were conducted to investigate the influences of key factors including voltage, electrode spacing and initial moisture content on the muck dewatering performance. The results show that under the optimal working condition, the moisture content of shield muck decreases from 42% to 23.4% and its fluidity drops from 18.45 cm to 11.05 cm after vacuum electroosmotic dewatering. During the dewatering process, the property evolution of shield muck presents an obvious dependence on moisture content, and penetrating cracks appear in high-moisture-content muck within 12 hours after the start of dewatering. In terms of residual moisture content of muck, the order of significance of influencing factors is: electrode spacing>initial moisture content>electrode arrangement mode>voltage. The tests verify the technical feasibility of applying vacuum electroosmosis to dewater shield muck, and the research findings can provide technical references for muck dewatering at shield construction sites under similar geological conditions.
由表1可知:砂卵石泥岩复合地层盾构渣土的渗透系数为4.2×10-5 cm · s-1,这说明渣土具有弱渗透性[19-20];盾构渣土含水率为38.2%,远高于其液限含水率28.7%。因此,渣土运输过程中为防止溢漏,运输成本大幅提高。并且这种高含水率渣土若直接集中堆填,还存在安全隐患。综上,出于安全和环保两方面考虑,对盾构渣土进行脱水处理十分必要。
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