Installation of a low-cost unsaturated soil monitoring system in Howick, South Africa

The stability of soil embankment slopes is an important aspect of infrastructure works, as many crucial roads, buildings and runways are ultimately supported by them. As changing climate patterns affect slope stability, the infrastructure in turn is put at risk. Increasingly, studies are being undertaken worldwide to investigate the effect of harsher climactic conditions on slopes using unsaturated theory, both by modelling and monitoring unsaturated slopes. This paper presents a low-cost suction monitoring solution incorporating fixed-matrix porous sensors for a 11 m high slope on a highway embankment in South Africa that had shown signs of movement prior to mechanical stabilisation works. An overview of the equipment and techniques used to install the system is given and data obtained from the system over a dry and a wet season is presented. The analysis of this data shows how material layering in the embankment can lead to localised zones of higher and lower suction which cannot necessarily be anticipated for design purposes without the air of direct measurement.