针对传统盾构渣土堆填过程中易引发环境与安全风险，以及处置成本持续攀升的问题，提出采用脲酶诱导碳酸钙沉淀（EICP）技术与工业副产物磷石膏相结合的协同固化方法，以探索该类渣土资源化处置新途径。通过改变磷石膏质量分数、EICP处理次数及考虑残余泡沫剂的影响，开展无侧限抗压强度、超声波速测试，并结合扫描电子显微镜观测，综合评价固化试样的力学性能演化规律。结果表明： 1）残余泡沫剂中存在的表面活性剂分子可吸附于黏土颗粒表面，通过增强颗粒间静电斥力有效改善EICP处理液的渗透均匀性，促进碳酸钙生成，从而使泡沫剂饱和环境中试样的无侧限抗压强度与超声波速均优于去离子水饱和环境中的试样。2）磷石膏的加入为EICP反应提供了额外的Ca2+，碳酸钙生成量增加，增强了胶结效果；但过量的磷石膏掺入会因细颗粒堵塞孔隙及提高孔隙液黏度而劣化渣土的渗透性，导致其固化性能下降。
High-water-content slurry containing residual surfactants produced during shield tunneling construction poses environmental pollution and safety risks when disposed of in traditional landfills. Furthermore, the diminishing capacity of disposal sites leads to continuously rising treatment costs. To address these challenges, this study proposes a synergistic solidification approach combining enzyme-induced carbonate precipitation (EICP) with the industrial byproduct phosphogypsum to explore a new pathway for the resource utilization of this type of slurry. By varying the mass fraction of phosphogypsum and the number of EICP treatments, and considering the influence of residual foaming agents, macromechanical tests such as unconfined compressive strength and ultrasonic wave velocity are conducted. Based on scanning electron microscopy observations, the mechanical properties and structural evolution of the solidified specimens are comprehensively evaluated. The results demonstrate the following: (1) Surfactants present in the residual foaming agent adsorb onto the surface of clay particles. This process enhances the electrostatic repulsion between particles, thereby improving the penetration uniformity of the EICP reactive solution and promoting the formation of calcium carbonate. Consequently, specimens prepared in a foaming agent environment exhibit superior unconfined compressive strength and ultrasonic wave velocity, compared to those prepared in a deionized water environment. (2) The addition of phosphogypsum provides sufficient additional Ca2+ for the EICP reaction, promoting additional calcium carbonate precipitation and enhancing the cementation effect. However, excessive phosphogypsum incorporation leads to pore clogging by fine particles and increased pore fluid viscosity, which reduces slurry permeability and consequently reduce solidification performance.
