Full-scale and model test study on CS-DSM technology

This paper presents an innovative contra-rotational shear deep soil mixing (CS-DSM) technology for ground improvement. The CS-DSM system features a coaxial dual-barrel design with independently controlled internal and external mixing blades rotating in opposite direction. This contra-rotational shearing mechanism enhances degree of mixing, prevents surface spoil, and improves construction efficiency. Field investigations involving coring, visual inspection, and unconfined compressive strength (UCS) testing validated the technology's effectiveness in achieving high-quality deep mixing columns with core recovery over 85% and UCS meeting design requirements. A small-scale model testing system was developed to address technical challenges for building the full-scale system. It served several goals: 1. verified the contra-rotational mixing feasibility, 2. optimized the mixing tool structure, 3. guided control system development, and 4. reduced research costs and time. Crucially, model tests established equation for computing the blade rotation number of CS-DSM column, and quantified the linear relationship between the blade rotation number T and UCS. This T-UCS correlation enables estimating the minimum blade rotation number for target strengths, optimizing quality and costs. In all, the CS-DSM technology integrated with the model-based design approach and robust process control demonstrates tremendous potential for efficient, high-quality ground improvement worldwide.