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Using a rock slope surface model generated from unmanned aerial vehicle (UAV) digital photogrammetry, this study develops a new semi-automatic dangerous rock blocks extraction approach. It consists of four steps: (1) three dimensional trace map extraction and projection; (2) convex polygon searching using a depth-first search algorithm and a sign consistency test; (3) true block formation analysis based on the geometric topology; and (4) block removability, failure mode and stability analyses using the edge vector, active resultant vector and limit equilibrium method, respectively. Compared with existing block identification methods, the proposed approach considers the contribution of line-type discontinuities on block formation and integrates geometric and mechanical modelling processes in one program. This approach is suitable for rockfall sources quantitative assessment. The locations, geometric parameters, and stability results of all identified blocks can be automatically obtained, and these could provide a reference for rockfall hazard assessment. The proposed approach is applied to a railway bridge case in China, and the corresponding rockfall hazard is evaluated. At the end of this paper, the joint sets related to block formation, uncertainties of block shapes, and discontinuity size effect are discussed. [ABSTRACT FROM AUTHOR]

• CT was applied to various types of soil that were collected in a reclamation area. • The coefficient of variation-based results showed the soil heterogeneity. • The averaged Hu was correlated with the physical properties and compressibility. • The averaged Hu values reflected the relative amount of soil particles and water. Nowadays, land reclamation by dredged soil has become an effective solution to the growing demand for land resources in coastal areas. However, the widespread dredger fill (artificial deposits in reclamation area) can compress the underlying soil layers, causing different degrees of land subsidence and posing a threat to infrastructure in relation to agriculture. Therefore, it is necessary to facilitate an understanding of the physical properties and compressibility of soil in the reclamation area. X-ray computed tomography (CT), as a non-destructive method, can provide insight into the structure of soil. In this paper, 44 undisturbed soil samples comprised of dredger fill, sandy silt, muddy clay, clay, and silty clay, were collected from ten 55 m deep boreholes in Chongming East Shoal reclamation area in Shanghai. CT and conventional tests were conducted on all soils. The coefficient of variation of the scanning-slice-related standard deviation was used to evaluate the soil heterogeneity, which reflects the spatial variability of the arrangement of soil particles. The results indicated that the slice-related coefficient of variation had a reliable capacity to evaluate the soil heterogeneity; the averaged Hounsfield (AHu) values of the soil sample had a significant statistical correlation with the conventional-test-derived physical properties (wet bulk density, dry bulk density, gravimetric water content, and porosity). The AHu values essentially reflected the relative amounts of soil particles and water in saturated soil. The granulometric compositions that can lead to denser arrangements of soil particles tended to have higher Hu values. A linear relationship was also found between AHu values and the compression index, which may help to predict the compressibility of the soil. As a rule, these findings open new avenues for research into the physical properties and compressibility evaluation of varied types of soil. [ABSTRACT FROM AUTHOR]