2019 Volume 14 Issue 1 Pages 43-56
Capillary barriers (CB) composed of a fine soil layer overlaid on a coarse soil layer exhibit excellent characteristics. Water which infiltrates into the soil is suspended just above an interface between the soil layers and diverted along the interface, with the result that a downward movement of water into the deeper soil layers below the interface is restricted for some length along the interface. Because of this diversion of infiltration water, the CB system has been employed in a top cover on waste landfills to reduce water infiltration into the protected waste materials. Also, the CB system is being considered as a top covering of shallow soil for extremely low-level radioactive waste repository and intermediate storage facility. However, there are still few examples of CB construction. Suitable materials for the fine soil layer and coarse soil layer used to make a CB are not confirmed. In particular, it is important to clarify that the fine soil has sufficient influence on the diversion length of the CB system. In this paper, the theoretical equation proposed by Ross-Steenhuis et al., fine soil permeability, water retention, are used to clarify an appropriate sand for maximizing diversion length. Moreover, a large soil layer experiment used fine soil with material properties that can maximize the diversion length of the CB system and clarified the material properties of a fine soil to maximize the diversion length of the CB. In addition, the authors clarified the applicability of the theoretical equation proposed by Ross-Steenhuis et al.
