Characterisation of High Rock Slopes using an Integrated Numerical Modelling - Remote Sensing Approach

Date created: 
Slope stability, numerical modelling, brittle fracture, discrete fracture networks, Vajont Slide, Delabole Quarry

During the last decade significant advances have been made in geomechanical modelling and remote sensing data acquisition techniques. These developments have allowed for improved rock slope stability analysis through consideration of the role of brittle fracture, kinematics and spatial variability in discontinuities within numerical models. This thesis investigates the role of several key parameters including damage, failure surface geometry and kinematics in rock slope failure using both conceptual slope geometries and natural and engineered rock slopes. Investigation of bi-planar and ploughing failure mechanisms in footwall slopes using the hybrid FDEM code, ELFEN, highlights the role of both brittle fracture in the development of secondary release surfaces and rock mass dilation in facilitating the slope failure. The bi-planar models show development of a highly damaged transition zone between the active and passive blocks. This failure mechanism is also observed in pseudo-two-dimensional bi-planar simulations using Slope Model. Three-dimensional simulation of non-daylighting wedges using Slope Model shows that this type of wedge, although apparently kinematically stable may in practice fail through stress concentration at the slope toe leading to failure of rock bridges, toe-breakout and slope collapse. Long-range terrestrial photogrammetry was conducted of the north-east slope of the Delabole Quarry, Cornwall, UK. The photogrammetry model was used to characterize rock discontinuities and to develop a realistic 3D geometry for subsequent distinct element analysis using 3DEC. The effect of selected input parameters (discontinuity friction angle, spacing and persistence) on the stability of the quarry slope was investigated using a deterministic approach. A stochastic approach using discrete fracture networks (DFN) was also employed to investigate the role of discontinuity uncertainty and spatial variability on the failure mechanism of the quarry slope. The deterministic and stochastic 3DEC-DFN models highlighted the role of kinematics and spatial variability of discontinuity characteristics on the slope failure mechanism, size and shape of the failed blocks.Lattice spring 3D simulations (using Slope Model) of the 1963 Vajont Slide, a catastrophic landslide that resulted in the loss of 1910 lives, clearly emphasized the role of brittle fracture, kinematics, block size and raised groundwater level on the failure mechanism. The Slope Model simulations conducted represent the first 3D brittle fracture simulation of the landslide considering the effect of groundwater on the failure.Innovative data post processing techniques are introduced throughout the thesis and used to gain a better understanding of the failure mechanisms of the modeled rock slopes. Damage extent parameters (ellipse of damage in 2D and ellipsoid of damage in 3D) are introduced and used to characterize the extent of the damaged zone within the numerical simulations. Inverse numerical velocity is also adopted within this dissertation to determine the numerical onset-of-failure and to better understand the regressive and progressive failure stages within the model simulations.

Document type: 
This thesis may be printed or downloaded for non-commercial research and scholarly purposes. Copyright remains with the author.
Senior supervisor: 
Doug Stead
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.