The initial, primary and secondary consolidation response of soft clay reinforced with a granular column under isolated loading

Abstract

This paper presents the assessment of consolidation and creep settlements of an isolated circular footing supported on soft clay samples reinforced with a single granular column. Clay samples (300 mm dia., 400 mm high) were formed from reconstituted kaolin and remoulded sleech (exhibiting significant creep). These samples were tested using chambers with various features to capture the settlement under constant foundation loading. In one model, the footing (70 mm dia.) was supported by a 40 mm dia. granular column formed by crushed basalt. The footings, with and without a granular column, were subjected to five vertical loading increments: 60, 120, 180, 240 and 300 kPa in the case of kaolin. In the case of sleech, vertical loading increments were: 60, 120 and 180 kPa. Each test lasted approximately ten months. In the case of kaolin, the settlement reduction factor was marginal, although it was considerably better for sleech. Kaolin exhibited marginal creep settlement under low to moderate bearing pressure, which increased substantially under high bearing pressures. Creep settlement was more prominent in sleech at all levels of bearing pressures. The very interesting finding from the investigation is that the settlement reduction factors due to consolidation and creep are similar in order under low to moderate loadings.