Investigation of the Extraction of the Casing for Large Diameter Cast-in-Place Piles by Vibratory Hammers in Clays

Abstract

The Benoto cast-in-place piles are widely used in civil engineering for having the advantage of producing low vibration and noise. Therefore, more researches are needed to fully understand its mechanism. However, the researches on the mechanism of Benoto piles are only limited to the driving stage, the study of extraction stage of the steel casing is not comprehensive. In this paper, a three-dimensional numerical model was developed by Coupled Eulerian–Lagrangian method. The mechanism of high-frequency vibratory extraction of casing was studied in detail. The result indicates that the vibratory casing extraction process can be divided into two stages, namely the slow and fast extraction stage. During the vibratory casing extraction process, the soil displacement, stresses, void ratio and excess pore water pressure abruptly change in the soils around the casing bottom. Furthermore, the influence of vibratory hammers on vibratory casing extraction was investigated. The change in the excitation frequency and excitation force has effect on casing extraction speed and soil particle velocity, but hardly has any influence on soil displacement and stresses.