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In this study, the generation process of the phreatic surface within a river levee is investigated through soil/water/air coupled simulation. Here, the effects of river level fluctuation and rainfall on changes in soil moisture distribution within a river levee are considered. The constitutive model proposed by Ohno et al.1) is formulated to the initial and boundary value problems in accordance with Borja's multi phases' concept and is used for simulation. Consequently, it is first found that high groundwater level is maintained for ground consisting of low permeability and high soil water retentivity. Moreover, it is found that the fluctuation of river level directly influences the phreatic surface, and that, in contrast, the effect of rainfall appears after a time lag.

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Consideration of influences of soil parameters on compaction behavior with soil/water/air coupled F. E. code Compacted soil is widely used for earth structures. However, the mechanism of compaction has not been explained, so it is difficult to grasp distributions of stress, void ration, and soil moisture within compacted earth structure. Therefore, estimation of safety and stability of compacted earth structures exposed to natural disaster is complicated. Compaction is decreasing void ratio by applying stress under certain water content and pushing air out of soil mass. Thus, the mechanics of unsaturated soil, which includes air within void, is needed for understanding of compaction. In this study, we regarded compaction as compression and expansion phenomenon of unsaturated soil under drained air and undrained water conditions and formulated it in initial-boundary-value problem. Here, the influences of permeability and soil water retention characteristics on compaction were considered and static compaction tests were simulated. Moreover, multi-layered compaction was examined.