NUMERICAL-ANALYSIS OF SOIL PLUG BEHAVIOR INSIDE OPEN-ENDED PILES DURING DRIVING

The plugging mechanism of infinitely-long open-ended piles is examined using numerical simulation of the wave propagation inside the soil pl ug and pile. It is shown that the key parameters for the plugging mech anism are the pile radius, the shape of the impact load, the shear wav e velocity of the soil inside the pile, and the friction at the pile-s oil interface. Consequently, the tendency of the pile to plug during d riving can be assessed prior to the driving process by consideration o f these key parameters. Existing one-dimensional models for the shaft response of open-ended piles are discussed and an improved model is pr esented. The differences between using one-dimensional models and fini te element models to simulate the plugging process are examined. The d ifferences are found to vary with the key parameters. Pile-in-pile and lumped-mass one-dimensional models are found to give satisfactory per formance for some parameter combinations, while for others an axisymme tric finite element model must be used. (C) 1998 John Wiley & Sons, Lt d.