| Heaving of the surface viscous layer lying on the permeable soil deposit at the toe of levees has occasionally been caused due to water pressure during flooding. However, there have been few cases of researching remedial methods to reduce water pressure applied to surface clay deposits under levees and to verify their effect. And no design method for countermeasures based on the effect of reducing water pressure has been established.Thus, model tests were performed to verify the effect of countermeasures to reduce water pressure and to establish a design method. Test of the model as an experiment was conducted using centrifuge model experiments and a full-scale mockup. In the model tests, a pervious toe trench was installed in the vicinity of the toe of levees as a countermeasure. The pervious toe trench replaces the viscous layer with crushed stone.The soil layer composition of the model was set by the typical composition to readily create water pressure in the surface viscous soil layer. The water level of the river was gradually raised to the top of the levees.As a result, the permeability coefficient of permeability of the trench could be confirmed in the full-scale experiment, and the effect of trench hydraulic permeability reduction could be understood through the centrifuge experiment. In addition, the effect of liquefaction has been confirmed to date by a reference oscillation experiment of centrifuge model tests. Furthermore, the scope of countermeasures was examined by parametric numerical analysis in which the kind of soil was changed so that it could be referred to in performance-based design in the future. |
