青岛地铁土压平衡盾构碎石土改良方法研究

Research on Conditioning Method of Gravel Soil in Qingdao Metro Shield Construction

盾构在碎石土地层掘进时经常面临着地层渗透性强、刀盘扭矩大、刀具磨损严重等诸多困难。为解决上述施工难题,以青岛地铁4号线典型的碎石土地层为研究对象,首先通过颗粒筛分、LCPC试验和渗透性试验评价了碎石土的基本特性,结合传统的砂土和黏性土改良方案设计了5组碎石土改良配比方案,对不同配比方案进行坍落度试验、渗透性试验和直剪试验,分析了不同改良指标碎石土的流塑性、渗透性及抗剪力学特性,根据实际工程中盾构刀盘扭矩的变化情况验证了泡沫与聚合物组合改良的最佳方案。研究表明:7%浓度泡沫与5%浓度聚合物配比的改良剂能够有效降低碎石土的渗透系数,同时起到降低刀盘扭矩的作用。

Shield tunneling in gravel stratum is often faced with many difficulties such as large torque of cutterhead,tool wear,and poor slag.Aiming at the research problem of reasonable conditioning index of gravel soil,the typical gravel soil layer of Qingdao Metro Line 4 is taken as the research object.Firstly,the basic characteristics of gravel soil are evaluated by particle screening,LCPC test,and permeability test.Five groups of gravel soil conditioning schemes were designed based on the traditional conditioning schemes of sand and clay soil.Slump test,permeability test,and direct shear test were carried out to analyze the flow plasticity,permeability and shear resistance characteristics of gravel soil with different conditioning indices.Finally,the best scheme of foam and polymer combination conditioning was verified according to the variation of torque of the shield machine in practical engineering.The results show that the mixture of 7%foam and 5%polymer can effectively reduce the permeability coefficient of gravel soil,maintain certain plasticity,and play a role in reducing the torque of the cutterhead and improving tunneling efficiency.