JRMGE / Vol 15 / Issue 5
Analysis of a landfill cover without geomembrane using varied particle sizes of recycled concrete
Charles Wang Wai Ng, Cheuk Lam Ng, Junjun Ni, Haowen Guo, Qi Zhang, Qiang Xue, Rui Chen
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a Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong, China
b School of Transportation, Southeast University, Nanjing, China
c State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071, China
d Department of Civil and Environmental Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen, China
2023, 15(5): 1263-1273. doi:10.1016/j.jrmge.2022.09.004
Received: 2022-04-11 / Revised: 2022-08-02 / Accepted: 2022-09-15 / Available online: 2022-10-04
2023, 15(5): 1263-1273.
doi:10.1016/j.jrmge.2022.09.004
Received: 2022-04-11
Revised: 2022-08-02
Accepted: 2022-09-15
Available online: 2022-10-04
Previous studies have demonstrated the effectiveness of a novel three-layer landfill cover system constructed with recycled concrete aggregates (RCAs) without geomembrane in both laboratory and field. However, no systematic investigation has been carried out to optimize the combination of the particle sizes for fine-grained RCAs (FRC) and coarse-grained RCAs (CRC) that can be used for the three-layer landfill cover system. The aim of this paper is to assist engineers in designing the three-layer landfill cover system under a rainfall of 100-year return period in humid climate conditions using an easily controlled soil parameter D10 of RCAs. The numerical study reveals that when D10 of FRC increases from 0.05 mm to 0.16 mm, its saturated permeability increases by 10 times. As a result, a larger amount of rainwater infiltrates into the cover system, causing a higher lateral diversion in both the top FRC and middle CRC layers. No further changes in the lateral diversion are observed when the D10 value of FRC is larger than 0.16 mm. Both the particle sizes of FRC and CRC layers are shown to have a minor influence on the percolation under the extreme rainfall event. This implies that the selection of particle sizes for the FRC and CRC layers can be based on the availability of materials. Although it is well known that the bottom layer of the cover system should be constructed with very fine-grained soils if possible, this study provides an upper limit to the particle size that can be used in the bottom layer (D10 not larger than 0.02 mm). With this limit, the three-layer system can still minimize the water percolation to meet the design criterion (30 mm/yr) even under a 100-year return period of rainfall in humid climates.
Keywords: Capillary barrier, Landfill cover, Particle size, Recycled concrete
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Author(s) Information
Charles Wang Wai Ng
Prof. Charles Wang Wai Ng earned his PhD degree from the University of Bristol, UK in 1993. After carrying out post-doctoral research at the University of Cambridge between 1993 and 1995, he returned to Hong Kong, joined HKUST as Assistant Professor in 1995 and rose through the ranks to become Chair Professor in 2011. As a world authority on unsaturated soil mechanics, eco-geotechnical engineering and landslides, Prof. Ng is the Fellow of the Royal Academy of Engineering, immediate Past President of the International Society for Soil Mechanics and Geotechnical Engineering (2017–2022), Changjiang Scholar (Chair Professorship in Geotechnical Engineering), Fellow of the Hong Kong Academy of Engineering Sciences, and Overseas Fellow of Churchill College, the University of Cambridge. He is also the Fellow of the Institution of Civil Engineers, the American Society of Civil Engineers, and the Hong Kong Institution of Engineers. Currently, he is a co-Editor-in-Chief of the Canadian Geotechnical Journal. Prof. Ng has supervised more than 60 PhD and 60 MPhil students to graduation, published 390 SCI journal articles and 250 conference papers and delivered more than 100 keynotes and state-of-the-art reports across the six continents. He is the main author of three reference books: (i) A Short Course in Soil-structure Engineering of Deep Foundations, Excavations and Tunnels by Thomas Telford in 2004, (ii) Advanced Unsaturated Soil Mechanics and Engineering, and (iii) Plant-Soil Slope Interaction by CRC Press in 2007 and 2019, respectively.