Sample Preparation Technique for Artificially Cemented Soils

Design of offshore foundations in cemented calcareous sediments requires a full understanding of the strength and deformation properties of the cemented soils. However, obtaining natural undisturbed samples from offshore sites is very expensive, and so there is a need to prepare reconstituted soils in the laboratory to replicate the natural material. Traditionally, cementing of the soils has been modelled by mixing Portland cement or gypsum powder with the uncemented soil in appropriate proportions to obtain a given strength. This note describes a new sample preparation technique to provide high quality lightly-cemented samples of consistent density. Although the technique is suitable for many different forms of cementing agents, it is used here in conjunction with the Calcite Insitu Precipitation System (CIPS), where cementation is effected by flushing a special solution through the soil, leading to precipitation of calcite on the soil grains. This leads to a form of cementation that simulates the natural material much more closely than using conventional particulate cementing agents. The sample preparation technique is described, and example results are presented for a range of soils. Comparisons are given between the stress-strain response of CIPS-cemented and Portland-cemented soil, with the former exhibiting more brittle behavior after failure, and a greater tendency for volumetric collapse.