Coupled continuum-discrete modeling of rammed floating stone column installation

To analyze the influence of stone column installation on the enhancement of soft ground and to reveal the physical aspects of the soil-pile interaction (SPI) mechanism, the stone column installation process is fully simulated by the three-dimensional continuous-discrete coupling (CDC) method for the first time. The stone column is simulated by particles in a discrete domain, the soft foundation and hammer are simulated by solid elements in a continuum domain, and the soil-pile interface and soil-hammer interface are simulated by coupling faces. Four installation effects, including the bottom enlargement effect, the branch effect, the heave effect and the penetration effect, are found during the installation process through the analysis of the displacement and stress field of the soft soil around the stone column. The bottom enlargement effect and the branch effect help improve the bearing capacity of the soft foundation, the heave effect helps to offset the ground subsidence, and the penetration effect reflects the penetration of the particles into the soft soil as they are punched by the hammer. Parametric studies of the stone backfill show that the average particle size, the friction coefficient and the bond strength ratio are linearly positively correlated with the displacement of the soil around the stone column, but the displacement of the soil decreases with a negative power law as the particle stiffness ratio increases. These research results are helpful for evaluating the influence of the stone backfill and the installation process on the reinforcement effect of the soft ground and for improving the accurate design and control level of soft ground strengthened by stone columns.