A novel vegetated three-layer landfill cover system using recycled construction wastes without geomembrane
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Article Full-text available November 2018 · Journal of Zhejiang University SCIENCE A
To promote environmental sustainability, recycled construction concrete is suggested for civil infrastructure works. The aim of this study was to investigate the effects of vegetation type on water infiltration under extreme rainfall conditions in a proposed three-layer landfill cover system containing recycled concrete. Three soil columns, namely bare, covered with shrub (Schefflera arboricola)
... [Show full abstract] and covered with grass (Cynodon dactylon), were subjected to ponding tests. Each column was compacted with a bottom layer of silty soil, an intermediate layer of coarse recycled concrete aggregate and an upper layer of fine recycled concrete aggregate. After 48 h of ponding, equivalent to a rainfall return period of greater than 1000 years in Hong Kong, water breakthrough occurred only in the bare cover system. Under the vegetated covers, suction maintained in the bottom silty soil layer was higher than under the bare cover by 49-52 kPa and hence no percolation was observed. Comparing the two vegetated cover systems, suction maintained under the shrub cover was 2-12 kPa higher (2-8% lower volumetric water content) than that under the grassed cover in the layers of recycled concrete. This implies that shrub cover can be more effective than grass cover in reducing water infiltration in humid climates. View full-text May 2015 · Environmental Earth Sciences
A common practice for disposing of municipal waste is to dump it in landfills, where it is then protected by a cover system. The main purpose of this cover system is to minimise the amount of water percolating into the waste and, hence, to reduce the excessive formation of leachate. To achieve this objective, conventional landfill covers employ low permeability materials, such as composite
... [Show full abstract] liners, to meet the permeability design criterion. However, their long-term hydraulic behaviour, cost and shear resistance are not entirely satisfactory. Increasingly, covers with capillary barrier effects (CCBEs) have been considered as an alternative cover system in semi-arid and arid regions. It is questionable, however, whether CCBEs can be successfully applied in humid climate conditions where the annual rainfall often exceeds 2000 mm. In this paper, an alternative three-layer capillary barrier cover system for use in humid climates is proposed, and its feasibility is investigated by a numerical parametric study. This alternative system consists of a fine-grained soil layer overlaying a coarse-grained layer, which in turn overlies a fine-grained soil, such as clay, to minimise water percolation in humid climates. This bottom clay layer is protected by the upper two coarser soil layers. The factors considered in the numerical parametric finite element analyses include the thickness of this additional clay layer, rainfall conditions and degrees of saturation of the municipal waste. It was verified that the middle sand layer serves as a capillary break when the rainfall intensity is light or the duration is short. After the upper two layers are permeated, the bottom clay layer serves as an impeding layer, whereas the sand layer shifts to serve as a lateral drainage layer. It was also found that the amount of percolation increases with an increase in rainfall duration but decreases with saturation of the waste. Based on the six simulated durations of rainfall, the most severe rainfall duration is 1 day, irrespective of the return period. Read more Article Full-text available August 2015 · Vadose Zone Journal
The design of existing soil landfill final covers, e.g., a single clay layer cover or a cover with capillary barrier effect (CCBE), aims at limiting water infiltration rather than minimizing landfill gas emissions. We propose an alternative three-layer capillary barrier landfill cover with an added clay layer underneath a CCBE to improve the effectiveness of limiting gas emission. Finite element
... [Show full abstract] analyses of coupled water and gas flow were performed to investigate and compare the performance of these three types of soil covers regarding gas emission under a continuous duration of 34 dry d. Due to evaporation, suction in the single clay layer cover increased larger than its air-entry value, causing a significant increase in the air coefficient of permeability. For the CCBE, evaporation also led to water loss in the silt layer, which cannot serve as a gas barrier. On the contrary, the bottom clay in the alternative three-layer capillary barrier cover system was protected by a relatively dry sand layer, which acts as a barrier, minimizing water loss from the clay layer. This is because the dry sand layer has a very low water permeability. As a result, the gas emission rate through the alternative three-layer capillary barrier cover was the lowest among the three types of covers. This rate was lower than the criterion set by the Carbon Farming Initiative, indicating that the alternative three-layer capillary barrier cover is a possible barrier to minimize gas emission even under dry weather conditions. View full-text Last Updated: 02 Feb 2019 Looking for the full-text?
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