EFFECTIVE COUNTERMEASURES TO PREVENT SOFT GROUND DEFORMATION CAUSED BY CONSTRUCTING WIDENING EMBANKMENT

The deformation properties of soft ground caused by the embankment construction for widening the existing single railway embankment have not been understood in detail. In this study, therefore, a centrifuge model test was performed to grasp deformation properties of soft ground for such construction mentioned above. We established suitable model preparation techniques for centrifuge tests to realize real condition at site, such as stress path of soft ground below embankment and construction procedure of the widening embankment and so on. The experiments revealed that large horizontal and vertical deformation occurred around bottom edge of the existing embankment, which induced the uplift of ground surface in front of the widening embankment and subsidence of existing embankment at the crest. Furthermore, shaking table model tests were also performed after the complete consolidation of the soft ground. Large deformation of the soft ground around bottom edge and in front of the widening embankment was observed. Based on these tests results, new countermeasure using wall type improvement method in combination with cement-mixed gravely soil slab is proposed.