ABSTRACT
A capillary barrier is a two-layer system of distinct hydraulic properties that is used as a cover system. The distinct hydraulic properties prevent water infiltration into the soil below the capillary barrier system by utilizing unsaturated soil mechanics principles. This paper illustrates the application of the capillary barrier system as a slope cover to prevent rainfall-induced slope failures. The capillary barrier was constructed on a slope which experienced a shallow slip surface. In this study, the capillary barrier system was designed as a cover system for slopes with a steep slope angle under heavy rainfall conditions of the tropics. The capillary barrier system was constructed using fine sand as the finegrained layer and granite chips as the coarse-grained layer. Both layers were contained in geocells. The slope was instrumented with tensiometers and piezometers. The tensiometers were installed at different depths from about 0.5 m to 2.0 m below the slope surface. In addition, the adjacent original slope without the capillary barrier system was also instrumented using tensiometers in order to investigate the performance and effectiveness of the capillary barrier system in reducing rainwater infiltration and maintaining negative pore-water pressure in the slope. The measurement results showed that the capillary barrier system was effective in maintaining the negative pore-water pressures during rainfalls. Results of field measurements and numerical analyses are presented in the paper. The measurement and numerical results were in agreement, demonstrating the use of unsaturated soil mechanics principles in capillary barrier system.
