Soil Plugging Effect of Sleeves Driven by High Frequency Hammers

In order to investigate the formation mechanism of soil plugging effect when a large-diameter bored-pile sleeve is penetrated by high frequency hammers, numerical simulation analyses were performed by using the 3D granular discrete element method. Variations in the displacements, velocities, contact stresses of soil particles inside and outside the sleeve, the height of soil plug and as well the porosity and shear stresses in soil plug with sleeve driving were investigated numerically. The numerical results show that the larger the high-frequency exciting force is, the larger the driving depth of a sleeve and the height of soil plug inside the sleeve are. At the meantime, the maximum fluctuation range and fluctuation amplitude of pore water pressure are large with the increase of the exciting force. Porosity in soil plug is larger at its top than at its lower part. During the process of the sleeve driven by a high frequency hammer, the maximum amplitude of pore water pressure appears at sleeve end. The larger the penetration depth is, the larger the pore water pressure becomes. Displacements of soil particles in the sleeve are small at the beginning. The contact number of soil particles at sleeve end raises with the increases of driving depth and vibration frequency. Moreover, contact stresses and shear stresses at sleeve end are larger than those in other regions.