title: Physical and numerical modeling of an inclined three-layer (silt/gravelly sand/clay) capillary barrier cover system under extreme rainfall.
abstract: As an extension of the two-layer capillary barrier, a three-layer capillary barrier landfill cover system is proposed for minimizing rainfall infiltration in humid climates. This system consists of a compacted clay layer lying beneath a conventional cover with capillary barrier effects (CCBE), which is in turn composed of a silt layer sitting on top of a gravelly sand layer. To explore the effectiveness of the new system in minimizing rainfall infiltration, a flume model (3.0 m × 1.0 m × 1.1 m) was designed and set up in this study. This physical model was heavily instrumented to monitor pore water pressure, volumetric water content, surface runoff, infiltration and lateral drainage of each layer, and percolation of the cover system. The cover system was subjected to extreme rainfall followed by evaporation. The experiment was also back-analyzed using a piece of finite element software called CODE_BRIGHT to simulate transient water flows in the test. Based on the results obtained from various instruments, it was found that breakthrough of the two upper layers occurred for a 4-h rainfall event having a 100-year return period. Due to the presence of the newly introduced clay layer, the percolation of the three-layer capillary barrier cover system was insignificant because the clay layer enabled lateral diversion in the gravelly sand layer above. In other words, the gravelly sand layer changed from being a capillary barrier in a convention CCBE cover to being a lateral diversion passage after the breakthrough of the two upper layers. Experimental and back-analysis results confirm that no infiltrated water seeped through the proposed three-layer barrier system. The proposed system thus represents a promising alternative landfill cover system for use in humid climates.
authors.affiliation: Guangzhou HKUST Fok Ying Tung Research Institute, Guangzhou 511458, China; Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Hong Kong Special Administrative Region.
authors.forename: Charles W W
authors.initials: CW
authors.lastname: Ng
authors.affiliation: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210098, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.affiliation: Shenzhen Key Laboratory of Urban and Civil Engineering for Disaster Prevention and Mitigation, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China. Electronic address: chenrui1005@hotmail.com.
authors.forename: Rui
authors.initials: R
authors.lastname: Chen
authors.affiliation: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210098, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Xu
mesh_terms: D004784:Environmental Monitoring; D008962:Models, Theoretical; D011891:Rain; D012037:Refuse Disposal / Q000295:instrumentation / Q000379:methods*; D012680:Sensitivity and Specificity; D012989:Soil Pollutants / Q000032:analysis*; D064091:Waste Disposal Facilities
chemical_list: D012989:Soil Pollutants
keywords: Capillary barrier; Extreme rainfall; Flume model; Landfill cover; Suction