Experimental Study on Effectiveness of Vertical Drains by Means of Rowe Cell Apparatus

Abstract

Vertical drains have recently become a popular method of soil improvement in Australia as it provides a low-cost solution for improving the performance of thick deposits of soft clays. The successful application of this method typically depends on the validity of analytical solutions in which settlements of soft deposits are predicted utilizing classical consolidation theories from soil mechanics. However, little has been done to test such theoretical models in practice, where different soil conditions can be encountered, primarily because project deadlines typically do not allow for such time-consuming endeavours. However, lack of reliable field and laboratory data may lead to a situation in which the effectiveness of soil improvement can be significantly below expectations, as recorded in some recent case studies. This research seeks to fill this gap in scientific data by presenting the results of experimental tests in which the behaviour of vertical drains was studied by means of a Rowe Cell apparatus. These tests were designed to investigate the influence of the size of vertical drains, as well as the smear effect, on settlements of soil at different stress levels. It was found that the process of consolidation occurred more rapidly when a drain of a larger diameter was utilized. In addition, similar to the results from large-scale field trials, it was observed that the presence of smear zone can also slow down the rate of settlement in the laboratory tests. Comparisons were made between different laboratory studies in which the performance of sand drains was investigated in a series of Rowe Cell tests. Finally, an attempt was made to compare the performance of vertical drains obtained in the laboratory tests with that which was observed in large-scale field projects.