Physical modelling of lime stabilisation in soft soils around deep excavations

Abstract

Bored concrete piles have been used widely on commercial developments in London for about the last 50 years. The life of a commercial building is between 25 – 30 years and, as each building is demolished and rebuilt, the piles from the previous buildings remain in the ground causing obstruct ions to the new foundations. This paper describes a preliminary study to explore the viability of sheet piled foundations as a genuine alternative to cast in situ concrete piles and all of the complications inherent in their construction and the obstruction they create to subsequent foundations. If it is possible to u se steel piles as foundations they can be easily removed, recycled and will not cause obstructions for future developments. However, individual sheet piles have relatively low capacity when axially loaded and it is therefore necessary to consider a sheet p ile grou p in conjunction with a pilecap, which can be considered a hybrid foundation; a combination of shallow (pilecap) and deep (sheet pile). A short series of centrifuge tests is reported in which model sheet pile groups in over - consolidated clay were l oaded axially whilst vertical displacements were measured. Equivalent cast in place piles were similarly tested alongside the sheet pile groups by way of comparison.