The Implementation Technology and Application of Rotary Drilling Full Casing Pipe of Secant Pile

The Hexi Resettlement Area Phase II project, part of the urban village renovation in Dongfeng Village, Conghua District, Guangzhou, encountered significant challenges including hole collapse, enlargement, and concrete over-pouring due to the presence of thick sand and gravel strata. These issues severely constrained project progress and conflicted with the principles of green construction. To effectively address these problems, the secant rotary bored pile method employing full sleeve casing technology was adopted. This paper systematically analyzes the implementation pathway and comprehensive benefits of this technology. The core of this technology lies in utilizing the full sleeve casing as a follow-up wall protection mechanism, creating a rigid barrier that completely isolates the detrimental effects of the unfavorable strata on the borehole wall. This ensures exceptional verticality of the pile shafts, with deviations maintained below 0.5%. Concurrently, the casing provides effective confinement during concrete pouring, significantly reducing concrete over-pouring. The concrete filling coefficient was consistently controlled within a narrow range of 1.05 to 1.08. By replacing the traditional slurry wall protection method, this process substantially reduces slurry generation and discharge at the source, while also effectively mitigating construction noise and vibration. Practical results demonstrate that this technology successfully overcame the complex geological obstacles, resulting in uniform and intact pile integrity. In terms of environmental benefits, it achieved multiple objectives: material saving, waste reduction, and noise abatement. Concrete over-pouring was strictly controlled, leading to a significant reduction in construction material waste; slurry discharge was drastically minimized, thereby alleviating environmental pollution in the surrounding area; and construction noise was effectively suppressed, reducing disturbance to nearby residents. This study confirms that the secant rotary bored pile method with full sleeve casing technology not only effectively resolves foundational construction challenges in specific geological conditions but also demonstrates significant advantages in technical-economic performance and environmental protection. It provides a reliable technical pathway and practical reference for similar engineering projects, underscoring its considerable value for widespread application.