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.

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It is envisaged that flood plains will be put into more active usage to meet the increasing demands for road infrastructural development as well as relieve the pressure exerted on arable lands owing to infrastructural development activities. This is consequent upon the general shortfall in the availability of soils possessing the right engineering properties to carry infrastructures such as roads which consume large tracks of land. Expanding the global infrastructural base is inevitable due to the ever increasing human population and the need to meet their social, economic, political and transportation needs. However, owing to the prevailing environmental awareness campaigns fronted by different environmental agencies, there is the need to regulate and monitor the interaction of the processes involved in the provision of these needs with the limited resources as well as the environmental aftermath associated with such operations. The stabilization of flood plain soils for road embankment construction is envisaged to reduce the demand on the material resources required to build classical high embankments in flood prone areas as well as offer implied mitigating dimensions in the restoration of environmental integrity. This impliedly will reduce the use of traditionally unsustainable methods of soil stabilization such as, the excavation and importation of new materials, to a more robust system that will offer environmental friendliness amidst value engineering for better strength and durability results. The experimental processes involved the simulation of flooding scenarios in the laboratory, to monitor the strength and durability aspects of low-bearing-capacity soils (such as Lower Oxford Clay) stabilized with blended mixes of the traditional stabilizer of lime and the novel materials of lime and Ground Granulated Blastfumace Slag (GOBS) by-product combined. Preliminary investigations were carried out on the Lower Oxford Clay soil to establish the moisture and compaction requirements of the material. Different mix compositions were formulated by incrementally replacing the amount of lime in the system with GOBS. This was based on the premise that high stabilizer contents could offer better stabilization to flood susceptible geo-materials upon flooding. A high stabilizer level of 16% was therefore investigated. Regimes of different blending ratios were established as follows: 16%Lime-0%GGBS, 12%Lime-4%GGBS, 8%Lime-8%GGBS, 4%Lime-12%GGBS and 0%Lime-16%GGBS and tested at moisture contents of 23%, 28%, 33% and 38%. The two extremes 16%Lime-0%GGBS and 0%Lime-16GGBS were used as controls. A system of elimination based on strength criteria was employed, where only the 8%Lime- 8%GGBS and 4%Lime-12%GGBS mixtures were deemed fit to be investigated further to determine their resistance to challenging environmental factors of flooding. The test samples were cylindrical, measuring 50 mm in diameter and 100 mm long, and these were compacted using a static compaction apparatus to achieve Maximum Dry Density (MDD). Depending on the testing regime to be applied to a given specimen, a curing pattern was defined and samples were wrapped in cling film to minimise moisture losses. At the end of each curing period of 7, 14, 28, 56 and 90 days, one of the experimental procedures which ranged from Unconfined Compressive Strength, Water Absorption, Volume Stability, Permeability, Soaked Strength and Durability Index Assessment or Compressibility Assessment was carried out on the moist cured samples. Following these assessments, the 4%Lime-12%GGBS mix composition was appraised to have overall improved characteristics with the added benefit of reduced cost of material utilisation. Based on the available data, regression analyses were carried out and equations established for predicting the strength values of stabilized materials. Using these equations further extrapolations were made and the observable trends were those of the dependence of compressive strength on the age of moist curing and the compaction moisture contents at which samples were produced at given blended mixture. Cost-benefit-risk analysis was also carried out with a further cost annualisation of the capital and operational cost of a selected system. It is reassuring to learn that at replacement level of lime with GOBS of 4%Lime-12%GGBS it was possible to establish multi-binder mixtures that could be effectively used for sustainable construction in flood prone areas with enormous savings accruing from the possible higher strength and enhanced durability indices achievable over traditional unsustainable options of continued over-reliance on lime and Portland cement.

Les structures en enrochements sont parmi les ouvrages les plus usuels de génie civil (barrages, murs de soutènement,. . . ). Des tassements importants peuvent apparaître tout au long de leur durée de vie et sont principalement dus à la rupture des blocs rocheux. Cette thèse propose un modèle numérique permettant de simuler le comportement de matériaux granulaires présentant des ruptures de grains. Afin de prendre en compte la nature discontinue de ces milieux, la méthode des éléments discrets est utilisée. La modélisation adoptée est de type "Non-Smooth Contact Dynamics", où les grains et particules sont supposés rigides. Afin de générer des blocs ayant des formes complexes, un modèle de grain 3D est proposé. Ce modèle de grain est ensuite discrétisé en sous-éléments de forme tétraédrique liés par des liaisons cohésives afin de pouvoir représenter la rupture. Un critère de rupture de Mohr-Coulomb est utilisé. Le modèle est implémenté sur la plateforme logicielle LMGC90. Le modèle est d’abord éprouvé lors de simulations d’écrasement de blocs cassables entre deux plaques. Plusieurs paramètres contrôlant la résistance du grain sont étudiés : cohésion intergranulaire, taille, discrétisation, forme et orientation du grain. L’effet d’échelle observé sur ce type de matériau est vérifié. Le modèle est ensuite testé lors de simulations numériques de compression œdométrique d’enrochements. L’effet des paramètres du modèle et de l’assemblage du milieu granulaire est également étudié. Les simulations œdométriques sont confrontées à des résultats expérimentaux et présentent une bonne concordance. Enfin, des expérimentations numériques sont menées afin d’étudier les énergies mises en jeu dans ces essais. L’énergie de création de surface est estimée pour ce type de matériau. Les résultats sont proches des données de la littérature. / Rockfill structures are very popular among civil engineering structures (dams, retaining walls, . . . ). Important settlements can take place during the lifetime of these structures, settlements mainly caused by the breakage of rockfill grains. This thesis proposes a numerical model that allows the simulation of the behavior of granular materials exhibiting grain breakage. To take into account the discrete nature of these media, the discrete element method is chosen. The adopted strategy is the Non-Smooth Contact Dynamics method, where grains are considered to be rigid. To generate blocks having complex shapes, a 3D grain model is suggested. This grain model is then discretized into tetrahedral subgrains, joined together using cohesive bonds so that breakage can be simulated. A Mohr-Coulomb failure criterion is used for the cohesive bonds. The model is implemented into the LMGC90 software platform. At first, the model is tested in single grain crushing simulations between two plates. Multiple parameters controling the strength of the grain are studied : the intra-granular cohesion, the size, the discretization and the orientation of the grain. The scale effect that characterizes this type of material is verified. Then the model is tested in numerical simulations of œdometric compression of rockfill. The influence of the parameters of the model and of those of the granular medium are studied. The results of œdometric simulations are compared to experimental results, and present a good agreement. Lastly, numerical experimentations are conducted in order to study the energies that are brought into play in the simulations. The surface creation energy is estimated for this type of material. Results are close to the data provided in the literature.