Centrifuge Model Test on the Stability of a Clayey Ground Improved by Deep Mixing Method With a Low Improvement Ratio

In this study, centrifuge model tests and numerical analysis were carried out to investigate effects of improvement by deep mixing method (DMM). Model grounds used in model tests were (1) unimproved ground (easel), (2) improved ground with vertical soil columns under toe of slopes (case2), (3) improved ground with vertical soil columns under shoulder of slopes (case3), (4) improved ground with inclined soil columns under toe of slopes (case4), and (5) improved ground with inclined soil columns under shoulder of slopes (case5). The improvement ratio was about 10% for all test cases except easel. The embankment was constructed by sand dropped from the sand hopper under 56g centrifugal field. Following conclusions were obtained from the model tests and the numerical analysis. 1) The deformation of ground was considerably controlled in spite of adopting the low improvement ratio of 10%. 2) For preventing the failure or the large deformation of ground, ground improvement just below the shoulder of the slope was more effective than that bellow toe of the slope. 3) Numerical analysis by means of FEM could be utilized to simulate the tendency of deformation behaviors of soft grounds