Development of an instrumented settling column for use in a geotechnical centrifuge

A geophysically and geotechnically instrumented settling column is used in conjunction with a geotechnical centrifuge, to monitor changing physical properties during the self-weight consolidation of a kaolin clay slurry. The column was equipped to monitor changes in excess pore pressure, bulk density and compressional wave velocity. The kaolin sample discussed in this paper was subject to an acceleration field of 100 g. The sample achieved 100% primary consolidation within 3 hours, excess pore pressures dissipating in a manner similar to that reported for 1 g settling column experiments. During this time the sample settled from a 0.865 m thick suspension to a 0.150 m thick soil deposit. The compressional wave velocity and density data, collected at one point in the sample, provided insight into the development of the soil during the centrifugation process. These data showed that below 1200 kg/m(3) the sample behaved as a suspension, which is comparable to the results of other researchers and consistent with suspension theory. Above this density, the experimental data indicates that the sample begins to develop a fabric and, as a consequence, the compressional wave velocity increases to values greater than those predicted by suspension theory. There are some issues which need to be resolved through further data analysis or centrifuge tests, but the principle aim of the experiment was successfully achieved. That is to demonstrate that the instrumented settling column for use in geotechnical centrifuge is an extremely useful technology for evaluating soft soil properties and behaviour in a time efficient and cost effective manner.