Groundwater characterization and modelling in natural and open pit rock slopes

The stability of rock slopes is often compromised by the presence of groundwater in the discontinuities within the rock mass. Discontinuities form the major pathways for groundwater flow and result in seepage zones along slopes. The hydrogeological characterization of fractures is, hence, an important task in rock slope investigations. Nevertheless, most current techniques require direct access to the rock slope, which can often be severely limited due to access, safety and the limited coverage of survey methods. In an attempt to both complement and overcome existing limitations of current methods, the present research makes use of remote sensing techniques to implement a window mapping approach to allow for the collection of structural and seepage information over a wide spatial area. Photogrammetry, ground based LiDAR and Infrared Thermography (IRT) are discussed. Research is also undertaken investigating continuum, discontinuum (distinct element model) and lattice-spring scheme modelling applied to assess the effect of groundwater on large open pit rock slope stability. Fluid flow within a fractured rock mass occurs as a coupled process where the flow field is influenced by the stress field and changes in stress resulting in changes in pore water pressures within the rock mass. The key findings gathered through this research highlight the importance of considering the use of coupled field and state-of-the-art remote sensing techniques in the characterization of seepage areas on high engineered and natural rock slopes. Similarly, numerical codes provided meaningful ways to account for the effect of incorporating groundwater in slope stability analysis. The continuum code, Phase 2, is shown to be suitable for simulating non-fracture controlled slope analysis. Nevertheless, limitations exist when groundwater flow is mainly affected and controlled by the fractures defining the rock mass. The conventional UDEC code is shown to be useful at providing information on the effect of the inclusion of pore water pressures, UDEC-Voronoi/Trigon is demonstrated to be an innovative and meaningful technique to account for the development of stress-induced brittle fracturing. The newly developed lattice-spring Slope Model is proven to be a useful means to assess the role of groundwater conditions on slope instability.