Numerical analysis of the effects of climate change on slope stability

Abstract

Embankments and cuttings form an integral part of the infrastructure of the UK. These earthwork structures are susceptible to a number of external influences which can ultimately affect their stability. Climate is one of these influences. There have been many observational correlations drawn between climate and slope deformation and eventual failure. A change in climate is therefore likely to impact on slope stability. It is widely agreed within the scientific community that the climate is changing. Future climates are likely to consist of higher average temperatures, wetter winters and drier summers. It is therefore important that we assess the impacts of future climate on slope stability in order to maintain vital infrastructure. This thesis describes the development of a novel numerical modelling procedure which allows the assessment of the effects of climate on slope deformation and rate of failure. The procedure employs the use of established hydrological and geotechnical numerical models to firstly calculate the pore pressure response to climate and secondly calculate the mechanical response to pore pressure. The hourly climate data required by the modelling procedure can be obtained from MET office weather stations for back analysis simulations or can be generated for present and future climates using a weather generator. The numerical modelling procedure has been used with present and future climatic data to assess the impacts of climate change on a diagnostic embankment and a cutting in the Newbury area. The procedure has also been used with historical weather data to back analyse an instrumented natural slope in Belfast, in order to determine the failure mechanism. The development and implementation of the modelling procedure lead to the following key findings. Firstly, laboratory and field permeability measurement techniques are wholly inadequate in measuring macroscopic permeability characteristics of clay slopes. Secondly, slope deformation magnitude is closely linked to annual maximum pore pressures. Wet years and increased wet year frequency will therefore considerably increase deformation and failure rate. Thirdly, the permeability of a slope will determine whether it will be more or less susceptible to increased failure rates when subjected to a future climate scenario. The strength of the study presented here is the amalgamation of the three separate disciplines of climatology, hydrology and geotechnical engineering in order to quantify the significance of each on the stability of slopes.