Design and Numerical Analysis of Road Embankment with Low Improvement Ratio Deep Mixing Method

As a measure to reduce lateral deformation and settlement due to road embankment loading on the soft clay ground, the column type Deep Mixing method used at a low improvement ratio of around 10–20% (LiDM) has been found to have sufficient performance and to save total costs. The main features of this method can be summarized as follows: (1) Since the whole bottom surface of embankment is improved all over, shear deformation toward outside of embankment due to settlement at the center part can be reduced compared with the conventional type. (2) Since the volume of embankment can be saved due to sufficient reduction of settlement, LiDM is considered to be environment-friendly. (3) When the column diameter is small (60–80 cm), small sized installation equipment and a simple loading test for quality control can be used. A rational design procedure for the LiDM has been formulated based on the results of laboratory model test. This paper reports on a study of this design procedure's suitability, using some cases of numerical analysis and case study of the expressway widening project near Bangkok in Thailand. It further discusses the improvement mechanism of the floating type Low improvement ratio Deep Mixing method.