土压平衡盾构穿越透水砾砂层渣土改良试验研究

摘要

土压平衡盾构在透水砂性地层掘进时,通常会出现不同程度的渣土喷涌问题,严重时可能威胁盾构隧道管片衬砌结构的安全.针对土压平衡盾构穿越深圳地铁7号线大沙河段透水砾砂层掘进施工,采用钠基膨润土与CMC作为渣土改良基材,开展透水砂层土压平衡盾构掘进渣土改良室内试验,揭示了改良剂浓度、掺量及不同组合对渣土改良效果的影响规律,并据此提出具有针对性的配比方案.研究结果表明:钠基膨润土泥浆对饱和砾砂改良效果显著,膨润土泥浆与CMC混合使用可以进一步降低改良土体的渗透系数,提升土体改良效果;结合工程实际给出膨润土泥浆浓度为11%、膨润土浆液与渣土体积比为1∶4的改良方案,通过对改良后渣土状态、盾构施工参数及地表沉降控制效果的综合分析,验证所提渣土改良方案的可行性.%Earth pressure balanced shields driving in permeable sandy stratum usually faces spewing sediment of different degree, which may endanger the shield tunnel segment lining structure.Based on the project of EPB shield driving in soils with permeable gravel sand of Line 7 in Shenzhen metro, Sodium bentonite and CMC are used as the main materials for sediment improvement to carry out the laboratory test and identify the influence of the modifier concentration, the amount of admixture and different combinations on sediment improvement.The targeted proportion scheme is then proposed.The research results show that the effect of sodium bentonite slurry on the improvement of saturated gravel sand is remarkable.Bentonite slurry mixed with CMC can further reduce the permeability coefficient of the improved soil and upgrade soil improvement.The practical engineering suggests 11% of bentonite slurry concentration and 1∶4 of bentonite slurry and sediment volume ratio.The condition of sediment after improvement, the shield excavation parameters and ground settlement monitoring data are statistically analyzed to verify the applicability of the laboratory scheme.