Performance of geosynthetic-encased stone column groups in soft clay: field tests and numerical study

Ground improvement is essential when constructing on soft soils with low shear strength. While ordinary stone columns (OSCs) are commonly used, their effectiveness is limited in very soft soils due to inadequate lateral confining support. This is due to a lack of lateral support. Geosynthetic-encased stone columns (GESCs) provide additional lateral support and improve load-bearing capacity. This study compares GESCs and OSCs in a soft clay layer. Field load tests were conducted in Kurimamachi Yachō, Mie Prefecture, Japan. Numerical simulations were validated using PLAXIS 3D (v22). Instruments like earth pressure cells (EPCs) and piezometers measured stress distribution and excess pore water pressure (EPWP). Results showed OSCs had lower EPWP at low stress but higher EPWP at high loads due to clogging. In contrast, GESCs showed greater stress concentration with larger area replacement ratios. The critical column length for maximum bearing capacity was about 6.67 times the column diameter. A predictive model and design charts were created to match published test results. This will help engineers optimize GESC-improved ground design in construction projects.