Abstract
Capillary barrier system (CBS) was developed as a slope protection method to prevent rainwater infiltration into the underlying soil based on the principle of unsaturated soil mechanics by harnessing the distinct difference in hydraulic properties of a fine-grained layer with those of a coarse-grained layer of soils. The CBS is commonly designed and constructed using gravel as coarse-grained material and fine sand as fine-grained material. However, due to scarcity of natural aggregates and in consideration of environmental sustainability, there is a need to utilize recycled materials in capillary barrier system. In this project, coarse and fine recycled concrete were used as the coarse- and fine-grained materials, respectively. The appearance of CBS was enhanced with an additional layer of approved soil mixture (ASM) to incorporate vegetation as green cover. CBS as a sustainable slope cover has been constructed for slope protection surrounding basement carpark in the new public housing development at Matilda, Singapore. The design, construction and monitoring system for the CBS are presented and discussed in this paper. The field measurement data provide verification of the performance of the CBS. Both field measurement and numerical analyses demonstrated that CBS performed well as designed.
Highlights
Capillary barrier system (CBS) is a cover system commonly consisting of a relatively fine soil layer placed over a relative coarse soil layer ([1], [2])
The objective of this paper is to describe the construction and performance of the CBS as a sustainable slope cover which was constructed surrounding basement carpark of HDB flats in Matilda, Singapore
The grain-size distribution (GSD) of materials used in CBS must be checked against the requirement in the specification (HDB, 2016) [19] as presented in Figure 6 before they were placed on site
Summary
Capillary barrier system (CBS) is a cover system commonly consisting of a relatively fine soil layer placed over a relative coarse soil layer ([1], [2]). CBS has been studied as a soil cover for landfill and mines wastes to reduce water infiltration ([3], [4]). Rahardjo et al (2012) [7] carried out parametric studies on three capillary barrier models and suggested to use a material combination with a \w-ratio, which is the ratio of the water-entry values of the fine- and coarse- grained layer, greater than 10. Rahardjo et al (2020) [12] indicated that recycled construction material such as RCA could have similar performance as the natural sand in the capillary barrier. The scope of works includes the installation of comprehensive instruments to provide real-time monitoring of rainwater infiltration into the slope and numerical analyses to assess the performance of CBS as a sustainable slope protection against rainfall-induced slope failure
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