Case study of a driven pile foundation in diatomaceous soil. II: Pile installation,dynamic analysis,and pore pressure generation

This paper presents the results from a case study highlighting the difficulties of pile driving in diatomaceous soils. In the companion(first) paper to this article, results of an extensive laboratory and in situ testing program were presented while the results from pile driving and further analysis of field observations were presented herein. Unexpected high pile rebound(HPR) was observed during driving of a closed-end pipe pile, with refusal occurring at a depth of less than 5 m. Subsequent open-ended piles were thus driven. Piezometer and case pile wave analysis program(CAPWAP) data were collected during driving of both closed-and open-end piles. Piezometer data indicated that negative pore water pressures(PWPs) were generated while the closed-ended pile exhibited high rebound. Results from in situ tests indicated change in material stiffness and strong dilative tendencies near the depth of refusal. A hypothesis for observed behavior was proposed that considers the soil beneath the pile as a medium with an effectively infinite bulk modulus.