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Abstract:
Insufficient soil compressibility and high adhesion in earth pressure balance (EPB) tunneling can elevate cutterhead thrust resistance, clogging risks, and equipment wear, significantly reducing efficiency and safety. Proper soil conditioning serves as an effective solution for enhancing tunneling performance; however, its effectiveness in dynamic tunneling requires comprehensive evaluation of compression-adhesion behavior. In this study, laboratory experiments were conducted using an improved push-pull dynamometer to examine the effects of gravimetric water content (w), foam injection ratio (FIR), fines content (FC), and clay mineralogy, focusing on clay, sand, and binary mixture. Complementary microstructural characterization using both optical microscopy and field emission scanning electron microscopy provides mechanistic understanding into the mechanical behavior at particulate scales. The experimental results demonstrate that the generalized compression modulus (Es) of clay, sand, and binary mixture is significantly reduced by foam conditioning. Quantitative analysis reveals exponential dependencies of Es on void ratio, FIR, and FC. Kaolinite-rich mixtures exhibit an exponential decrease in Es with increasing FC, while montmorillonite-rich ones show polynomial dependence with a critical FC threshold. Regarding normal adhesion stress (NA), the effectiveness of foam conditioning is found to be dependent on both w and FC. Binary mixtures display an exponential correlation between NA and FC, whereas clay follows a rational function relationship between NA and w. All measured NA peaks are consistently observed within the consistency index range of 0.00-0.50 across the full spectrum of tested FIR conditions (0-120 vol%). This study provides valuable insights for optimizing soil conditioning parameters in EPB shield tunneling under varying geological conditions, while demonstrating the potential of in-situ fine-grained soils as effective conditioning agents.
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TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY
ISSN: 0886-7798
Year: 2026
Volume: 167
6 . 7 0 0
JCR@2023
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ESI Highly Cited Papers on the List: 0 Unfold All
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30 Days PV: 2
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