地铁盾构穿越富水砾砂地层渣土改良试验研究

富水砾砂地层具有内摩擦角大、渗透性强等特点,在盾构掘进时容易造成螺旋输送机堵塞或刀盘结泥饼等工程事故。通过改变含水率、泡沫剂浓度及膨润土泥浆浓度,测试砾砂渣土的坍落度得到其变化规律,同时观察土样的流塑状态,采用析因试验设计理论对多因素影响渣土改良试验效果的耦合作用进行显著性分析。研究结果表明:含水率是影响渣土改良试验的主要因素,最优坍落度范围为185～200 mm;当含水率为5%时,坍落度随着改良剂浓度的增高逐步降低;当含水率为16%时,坍落度随着改良剂浓度的增高而增大。对坍落度的显著性影响从大到小依次为含水率(A)、一级交互作用(A×C、A×B)、膨润土泥浆浓度(C)、一级交互作用(B×C)、泡沫剂浓度(B)、二级交互作用(A×B×C)。基于现场试验与等值关系图,得到最优坍落度对应的含水率、泡沫剂浓度、膨润土泥浆浓度范围分别为10.6%～14.2%、 2.5%～4%、11%～13%,研究结果对于提高富水砾砂地层的盾构掘进效率具有重要的指导意义。

Experimental Study on the Improvement of Muck Soil by Subway Shield Crossing Water-rich Gravel Sand Stratum

The water-rich gravel sand stratum has the characteristics of large internal friction angle and strong permeability, so it is easy to cause the engineering accidents such as spiral conveyor blockage or mud cake formation on the cutter during shield tunneling. By changing the moisture content, foam concentration and bentonite mud concentration, the slump of gravel and sand slag was measured to obtain its change law, and the fluidity-plastic state of soil samples was observed. The orthogonal experiment design theory is used to analyze the significant analysis of the coupling effect of multiple factors influencing the test effect of slag improvement. The result shows that moisture content is the main factor affecting the slag improvement test, and the optimal slump range is 185 mm～200 mm. When the moisture content is 5%, the slump gradually decreases with the improver increase of the improver concentration. When the moisture content is 16%, the slump increases with the concentration The significant effects on slump are moisture content (A), first-order interaction (A×C, A×B), bentonite mud concentration (C), first-order interaction (B×C), foam concentration (B), and secondary interaction (A×B×C). Based on the field test and the equivalent relationship diagram, the ranges of water content, foaming agent concentration, and bentonite slurry concentration corresponding to the optimal slump respectively are 10.6%～14.2%, 2.5%～4%, 11%～13%. The research result has important guiding significance for improving the efficiency of shield tunneling in water-rich gravel sand formations.