Abstract
Soil conditioning is a critical technology for ensuring tunnel face stability and excavation efficiency in Earth Pressure Balance (EPB) shield tunneling. Commonly used conditioning agents include water, foam, bentonite slurry, polymers, and other materials. While existing research has experimentally investigated foam-conditioned soil and bentonite-conditioned soil separately, studies on the combined use of foam and bentonite slurry and its effects on conditioned spoil properties are lacking. This study employs a self-developed laboratory testing apparatus to investigate the rheological and compressibility characteristics of sandy ground conditioned with foam-bentonite combinations, deriving the rheological mechanical equation of conditioned soil and the variation patterns of parameters including void ratio and compression. Based on the experimental results, optimal mix ratios for conditioned soil in three ground types—cobble, gravelly sand, and medium-coarse sand—were determined, and evaluation criteria for soil conditioning in sandy strata were established. This research provides technical support and theoretical guidance for soil conditioning technology in sandy strata, and offers judgment standards for practical construction applications.
Full Text
Preamble
Study on Improving the Flow Plasticity of Shield Muck in Sandy Strata Using Foam-Bentonite Synergistic Amendment
Wang Zhiguo, Chen Danlian, Song Xuelu
(Guangzhou Metro Engineering Consulting Co., Ltd., Guangzhou 510000, China)
Abstract
Muck conditioning represents a critical technology for ensuring face stability and advancing efficiency in earth pressure balance (EPB) shield tunneling. Conventional conditioning agents encompass water, foam, bentonite slurry, and polymers. While existing research has experimentally investigated foam-conditioned soil and bentonite-conditioned soil independently, studies examining the combined effects of foam and bentonite slurry on conditioned muck properties remain limited. This research employs a self-developed laboratory apparatus to systematically investigate the rheological and compressibility characteristics of sandy soil improved through combined foam-bentonite amendment. The study establishes rheological constitutive equations and quantifies the evolution patterns of key parameters, including void ratio and compressibility. Based on experimental results, optimal mix proportions are determined for three distinct sandy strata: cobble, gravelly sand, and medium-coarse sand. Furthermore, the research proposes comprehensive evaluation criteria for muck conditioning in sandy formations. These findings provide both technical support and theoretical guidance for muck conditioning practices in sandy strata, while offering practical assessment standards for field construction applications.
Keywords: Earth pressure balance shield; muck conditioning; sandy strata; foam agent; bentonite slurry