Weather-driven deterioration processes affecting the performance of embankment slopes.

Deterioration of earthworks and the resultant implications for serviceability and increased occurrence of failures have a significant negative impact on transport networks both in the UK and internationally. There is evidence in the field that deterioration processes are occurring over the life of an asset, comprising cracking and loss of suction. These are weather-driven processes that occur in the absence of increased mechanical loads and can lead to failure many years after construction. To demonstrate the progressive loss in mechanical performance of clay fill due to a purely environmentally driven deterioration process, a programme of unsaturated triaxial testing was carried out. A new mechanism of soil deterioration driven by cyclic wetting and drying is proposed, based on an extensive laboratory and field experimental programme. The underlying cause for this is the micro-structural changes to the soil fabric leading to loss of suction generation capacity. In addition, cracking leads to changes in hydraulic conductivity and the movement of water into and out of the soil. The implications for slope stability assessment include the need for changeability of soil parameters and of the ground model, with changes occurring both seasonally and gradually over time