Development of a deep mixing model system on centrifuge platform

Abstract

Wet Deep Mixing (DM) is widely used for in-situ soil treatment. It involves mixing stabilizers, usually cement grout, with weak clayey soil to create soil-cement columns. However, it has been found that, in the field, the strengths of the DM improved soil can vary significantly from point to point. The strength variability of the DM columns is highly dependent on the mixing process during installation. Field tests for DMM is always quite costly and time consuming, so it is often unrealistic to conduct many field tests, and 1-g small scaled model test cannot reproduce the prototype situation for DM. Therefore, centrifuge model is a reasonable way to study the mixing process and uniformity problem. This paper presents the development of a model system for DM on the geotechnical centrifuge platform of National University of Singapore. The system includes a single-shaft DM model machine, a multi-shaft DM model machine, a series of DM installers and a sample postprocessing method. In the centrifuge tests, the mixing process is modelled in-flight under a high-g environment, with appropriate scaling considerations for column size, set times and binder characteristics. The design and fabrication of this centrifuge model system and test procedures are introduced. Then, preliminary results are discussed. © 2012 American Society of Civil Engineers.