Key Technology of Rapid Trenching Construction of Diaphragm Wall in Slightly Weathered Limestone Area

To address technical challenges in the construction of underground continuous walls within composite strata composed of micro fossilized limestone and water-rich sand layers—including high slot collapse risks, low milling efficiency in hard rock, difficult precision control during slot formation, and complex multi-process coordination—we conducted research on key rapid slot-forming technologies. Utilizing the civil engineering project at Ma'anshan Park Station along the Guangzhou East to Huadu Tiangui section of the Guangdong-Hong Kong-Macao Greater Bay Area intercity rail line as a case study, we developed a comprehensive rapid slot-forming system incorporating four core techniques: layered wall reinforcement using long-spiral mixing piles combined with high-pressure jet grouting, specialized bentonite slurry for composite strata, precise design of advanced guided holes, and collaborative slot formation through rotary drilling and milling. Field tests demonstrated that this technology effectively resolves slot collapse issues in water-rich sand layers, reducing average slot formation time from 28 hours (traditional method) to 13.75 hours for Phase I slots and 28 hours to 3.75 hours for Phase II slots, maintaining slot wall verticality within 0.38%, while cutting construction costs by 19.3%, energy consumption by 50.9%, and milling tool wear by 43.3%. Tailored to the characteristics of composite stratum construction, this system outperforms traditional methods in safety, quality, and cost-effectiveness, providing valuable technical reference for rapid slot-forming applications in similar complex geological conditions.