Breakthrough mechanism and performance analysis of natural capillary barrier with bentonite as finer layer

Abstract

Water retention is crucial in many applications, including canal irrigation, agriculture storage ponds, and mine tailings impoundments. A capillary barrier system (CBS) offers a promising solution by utilizing contrast in pore sizes between soil layers to minimize infiltration. However, the application of compacted bentonite as the finer CBS layer remains underexplored due to challenges in characterizing its unsaturated hydraulic behavior. Recent advancements in laboratory and theoretical studies provide an opportunity to evaluate its breakthrough response and mechanism under ponding conditions. This study presents a comprehensive hydraulic analysis of CBS incorporating compacted bentonite as the fine layer. Laboratory experiments were conducted to determine the soil-water characteristic curve and hydraulic conductivity function of the studied compacted soils, while one-dimensional column tests for breakthrough head, breakthrough time, water storage, and infiltration rates for various CBS configurations. The influence of bentonite plasticity and coarser layer density on CBS performance was systematically examined. Further laboratory investigations explored the impact of coarser layer soil type variations. A novel breakthrough mechanism was identified for CBS employing different soil as coarser layer. The laboratory and field scale tests demonstrate the suitability of compacted bentonite as an effective component in CBS designed for water retention applications.