Evaluating the condition and stability of coastal cliffs and assessing longevity of significant overhangs and undercuts in an active marine environment is a challenge. As part of cliff management studies undertaken for the Coastal Zone Management Unit of the government of Barbados, a programme of innovative cliff profile mapping was conducted around the island of Barbados. A combination of land-based field mapping information and fixed wing aircraft collected high-resolution LiDAR imagery was utilised for cliff geometry assessments, supplemented for specific cliff profiles by fill-in high-precision three-dimensional (3D) digital terrestrial imagery, captured by low level wide wingspan UAV drone flights. Comprehensive photogrammetric processing of this imagery, combined with detailed geographic information system software evaluation of the collected point cloud data, allowed generation of full 3D wireframe digital terrain and digital elevation models (DTMs and DEMs). Multiple representative cliff areas around the island were identified, allowing thorough 3D stability assessment to be accomplished of key problematic areas using Flac3D. Vertical cross-section profiles were also cut so that undercut and notched cliffs could be analysed in detail in two dimensions using Voronoi tessellation approaches applied within the universal distinct element code UDEC as a means to replicate the characteristics of the vuggy coralline limestone cliffs.
Defining shear strengths of concrete–rock contacts is extremely important for designing concrete structures such as arch and gravity concrete dams that are constructed on rock. Assessment of 34 large-scale in situ direct shear tests conducted on concrete–rock contacts of various roughnesses is presented in this paper. Evaluation of the peak strength results at moderate-to-low stress ranges, indicates that a non-linear trend with maximum at moderate roughness (joint roughness coefficient, JRC = 11–12) can reasonably represent relationships between peak and apparent shear strengths, shear stiffness and shear displacement relationships with respect to JRC. Apparent residual strength parameters appear to show a more linear Mohr–Coulomb to slightly non-linear trend with JRC and applied normal stress.
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