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