STUDY ON IMPACT ABSORBENCY OF SOIL MIXED WITH CRUSHED EPS WASTE – RELATION TO THE DEFORMATION CHARACTERISTICS OF SOIL –

As a contribution to solving environmental problems, some attempts at recycling waste into geomaterials have been carried out. The authors have also been investigating some possibilities to effectively use crushed EPS (Expanded Polystyrene) waste as a constituent of a light-weight mixed soil. The soil mixed with this crushed EPS waste needs; lightweight geomaterial strength properties, water retentivity and permeability for vegetation, an insulation effect and so on. Consequently, crushed EPS waste is expected to be used as a material for rooftop gardening foundations. In this study, focused on the cushioning function as a major characteristic of EPS, the impact absorption effect of soil mixed with crushed EPS waste was investigated. This is because by using this mixed soil as a rooftop gardening foundation, it is expected that the burden upon the legs and lower backs of the people who are resting there is reduced and that the propagation of discomforting vibrations caused by outdoor air conditioning units, to lower floors, is inhibited. Accordingly, a rammer was dropped on the mixed soil. The effect of decreasing the falling object’s impact acceleration and reducing the bearing foundation’s impact load, caused by using the mixture of crushed EPS waste, was examined. Then, the influence of the deformation characteristics of the mixed soil upon the impact absorbency was considered. As a result, it was found that the impact acceleration and bearing load were decreased in accordance with the crushed EPS waste mixture ratio. The ratio of decrease was almost in proportion to the decreasing ratio of mixed soil deformation modulus. Moreover, it was mostly found that the decreasing impact acceleration ratio was correlated with the elastic deformation component originating in the crushed EPS waste. These results are thought to give important information to clarify the mechanism of the impact absorption effect of soil mixed with various waste materials more easily deformed than soil particles. This is considered to contribute to the advancement of the effective use of recycled materials.