Performance of capillary barrier as a sustainable slope protection

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.