Edinburgh Napier University

  Stone columns installed in extremely soft soils may significantly reduce the effectiveness of this treatment due to the insufficient lateral confinement provided by the soft soil. The encasement of columns with geotextiles is commonly used in these situations with satisfactory results thanks to the extra confinement provided by the geotextile to the column. Drained triaxial tests on encased and non-encased samples of gravel have been performed to study the influence of the encasement on the behavior of stone columns. Two different densities of the gravel and two different geotextiles were used. The study is focused on the increase in strength of encased samples compared with non-encased ones, the extra confining pressure provided by the geotextiles and the mobilized friction angle of the gravel. In this paper, the results of some of these laboratory tests are compared with numerical simulation. All of the results show the improvement achieved when the gravel is encased with the geotextiles.