化学絮凝与消泡材料对盾构渣土渗流性能的作用机理

Mechanisms of Chemical Flocculation and Defoaming Materials on Seepage Characteristics of Shield Tunneling Residue

摘要:

为促进盾构渣土的资源化利用，针对土压平衡盾构渣土成分复杂、含水率高且渗透性差等问题，结合渗透试验、压汞测试和计算机断层扫描（CT）等方法，分析盾构渣土的多尺度渗流特征，探究掺入絮凝剂阳离子型聚丙烯酰胺（CPAM）和消泡剂有机硅氧烷对渣土渗透性能的影响和作用机理。结果表明：原状盾构渣土的水分渗流受土体内泡沫的影响，渗透系数最终稳定在7.72×10^-6 cm?s^-1附近，土体孔隙率高且孔径小贯通性差。絮凝剂的掺入可以改善盾构渣土的渗透性能，这是因为CPAM的吸附架桥和电中和作用，但掺量过大则会抑制渗流；该试验中CPAM的最佳掺量为0.30 %，渗透系数最高可达2.55×10^-5 cm?s^-1。消泡剂有机硅氧烷的掺量越高，盾构渣土的渗透系数越大，消泡剂可以快速消破土体内部泡沫并提高渗流通道的连通性；本试验的最佳掺量为0.20 %，渗透系数可达1.31×10^-5 cm?s^-1。

Abstract:

To promote the resource utilization of shield tunneling residue， this paper focuses on the complex composition， high moisture content， and poor permeability of earth pressure balance（EPB） shield tunneling residue. In combination with penetration test， mercury injection test， and computed tomography （CT）， the multi-scale seepage characteristics of shield tunneling residue were analyzed， and the effect and mechanism of flocculant cationic polyacrylamide （CPAM） and defoamer organosiloxane on the permeability of the residue were investigated. The results show that the permeability of shield tunneling residue is affected by the foam in residue， and the permeability coefficient is finally stable around 7.72×10^-6cm?s^-1. The residue has a high porosity， small pore size， and poor penetration. The addition of CPAM can improve the permeability of the residue due to the adsorption bridging and electric neutralization effects. However， excessive flocculant will inhibit the seepage. The optimal dosage of CPAM in this experiment is 0.30 %， and the maximum permeability coefficient can reach 2.55×10^-5 cm?s^-1. As the content of organosiloxane defoamer increases， the permeability coefficient of the residue increases， which can quickly eliminate the foam and improve the connectivity of seepage channel. The optimal dosage for this experiment is 0.20 %， and the permeability coefficient can reach 1.31×10^-5 cm?s^-1.