Effect of compaction density of sand layer on diversion capacity of capillary barrier

Abstract

A simple soil layer system composed of a finer soil layer overlaying a coarse soil layer exhibits an excellent property of capillary barrier (CB). 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 deeper soil layers below the interface is restricted within some length along the interface. Because of this diversion of infiltration water, the CB system has been employed in a top cover of waste landfills and mining wastes to reduce water infiltration into the protected waste materials. In designing the diversion capacity and constructing the CB system, a compaction density ρ_d (degree of compaction D_c) in the sand layer should be quantified because it affects the saturated hydraulic conductivity of the sand layer which determines the length of the diversion capacity of the CB system. In this paper, saturated hydraulic conductivity and soil-water characteristic curve (air- and water-entry pressures) of sand specimen are measured with changing its dry density by using a pressure membrane method, and the effect of the dry density of sand on the hydraulic properties of sand is investigated. A series of laboratory soil tank test is also conducted in order to study the effect of dry density of the sand layer on the diversion capacity of the CB system.