Numerical Simulation of Soil Stress State Variations due to Mini-Pile Penetration in Clay

Abstract

During installation of prefabricated piles in saturated clayey soils, excess pore water pressure (EPWP) is generated around the pile shaft and tip. The developed excess pore pressure is extremely important for evaluation of changes of stress state in clay and subsequent pile bearing capacity. Therefore, the main objective of this paper is to present a numerical finite-element model (FEM) to simulate a mini-pile installation and subsequent pore water pressure dissipation over time. The mini-pile is inserted from the ground surface into the soil to the desired depth. The numerical model is validated using the results of a physical model in which a piezocone is penetrated into a consolidation chamber containing saturated clay. The effects of Over-Consolidation Ratio (OCR), coefficient of lateral soil pressure (K 0), penetration rate (PR), and soil hydraulic conductivity (K i ) on soil stress state are investigated. The verification results have shown that the numerical model has successfully simulated the penetration of mini-pile, generation, and subsequently dissipation of the excess pore water pressure (EPWP). The parametric study revealed that increasing the OCR and K 0 has resulted in increase of the effective radial stresses on the pile skin compared to its initial value, after dissipation of EPWP. The results indicate that the variations in radial stresses at the end of dissipation are independent from the penetration rate. The dissipation of EPWP is more correlated with horizontal hydraulic conductivity of the soil, because the dissipation rate is accelerated in the radial direction.