Research on optimized mud wall protection tchnology for rotary drilling in deep soft soil formations

Borehole stability is a major technical challenge during rotary drilling of cast-in-place piles in deep soft soil layers , particularly those characterized by high water content, high compressibility, low shear strength, and pronounced flow plasticity. Conventional wall protection methods often fail to counteract the strong disturbance caused by dynamic drilling operations, frequently leading to hole collapse or diameter reduction, which compromises pile quality and project safety. To address this, a mud wall protection technology compatible with rotary drilling characteristics was developed. Through numerical modeling, the influence of key mud parameters on borehole stability was analyzed, showing that appropriately enhanced mud performance effectively balances soil pressure and controls deformation. Experimental design methods were then used to optimize a bentonite-based mud formulation with specific chemical additives, significantly improving mud cake quality and stability. Validated in field projects, the optimized mud demonstrated improved borehole stability. This research provides a scientific basis for mud design and a practical technical solution for rotary drilling in deep soft soils, contributing significantly to ensuring pile bearing capacity and project safety.