Pore pressure during stone column installation

Abstract

During stone column installation, mainly by the vibro-displacement method, the vibrator displaces the native soil laterally as it is advancing into the ground. As a result, the surrounding soil and its properties are altered. The study of these installation effects, whether they are positive, negative or negligible, is nowadays one of the major concerns for an accurate design of ground improvement techniques. As a part of a wider research, a field test was set up to have a better understanding of the installation effects of stone columns. The site characterisation, the layout of the instrumentation and its results are presented here. Pore pressure was recorded by six piezometers in a quasi-continuum way during the installation of the nearby columns. The peaks of pore pressure during the vibrator penetration are analysed and compared with the analytical solution of the cavity expansion theory. In this case the dissipation of the pore pressure in the radial direction is very fast, and there is no remaining excess pore pressure after a few hours. Laboratory tests on soil samples were carried out before and after the column installation.