M. Bahaaddini; M. Serati; M. H. Khosravi; B. Hebblewhite
Abstract
A proper understanding of the shear behaviour of rock joints and discontinuities is yet a remaining challenge in the rock engineering research works owing to the difficulties in quantitatively describing the joint surface roughness both at the field and the laboratory scales. Several instruments and ...
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A proper understanding of the shear behaviour of rock joints and discontinuities is yet a remaining challenge in the rock engineering research works owing to the difficulties in quantitatively describing the joint surface roughness both at the field and the laboratory scales. Several instruments and techniques have been developed over the years for the surface characterisation of joints at the field- and laboratory-scale investigations, amongst which the application of the photogrammetry methods has obtained a growing popularity. This work evaluates the applicability of the photogrammetry techniques for the characterisation of joint surface topography and texture at micro-scales, which has been largely understudied in the literature. Three tensile joint surfaces are digitized using photogrammetry, and the results are compared with those obtained from laser scans with a high 3D accuracy. A comprehensive statistical analysis is then undertaken on the digitized point clouds in order to assess the performance of photogrammetry in surface characterisation. The results of this work show that the height differences between the resulting point clouds from the two adopted techniques (photogrammetry and 3D laser scanning) follow the normal distribution with the mean values close to zero. The statistical analyses illustrate that the measured joint surfaces using the photogrammetry techniques are in good agreement with the laser scanning data, confirming that photogrammetry is a capable method for characterising the joint surface roughness even at micro-scales. Interestingly, the results obtained further indicate that the accuracy and preciseness of the photogrammetry techniques are independent from the joint roughness coefficient but the camera and configuration parameters remarkably control the performance of the measurement.
M. Ghaedi Ghalini; M. Bahaaddini; M. Amiri Hossaini
Abstract
Estimation of the in-situ block size is known as a key parameter in the characterization of the mechanical properties of rock masses. As the in-situ block size cannot be measured directly, several simplified methods have been developed, where the intrinsic variability of the geometrical features of discontinuities ...
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Estimation of the in-situ block size is known as a key parameter in the characterization of the mechanical properties of rock masses. As the in-situ block size cannot be measured directly, several simplified methods have been developed, where the intrinsic variability of the geometrical features of discontinuities are commonly neglected. This work aims to estimate the in-situ block size distribution (IBSD) using the combined photogrammetry and discrete fracture network (DFN) approaches. To this end, four blasting benches in the Golgohar iron mine No. 1, Sirjan, Iran, are considered as the case studies of this research work. The slope faces are surveyed using the photogrammetry method. Then 3D images are prepared from the generated digital terrain models, and the geometrical characteristics of discontinuities are surveyed. The measured geometrical parameters are statistically analysed, and the joint intensity, the statistical distribution of the orientation, and the fracture trace length are determined. The DFN models are generated, and IBSD for each slope face is determined using the multi-dimensional spacing method. In order to evaluate the validity of the generated DFN models, the geological strength index (GSI) as well as the stereographic distribution of discontinuities in the DFN models are compared against the field measurements. A good agreement has been found between the results of the DFN models and the filed measurements. The results of this work show that the combined photogrammetry and DFN techniques provide a robust, safe, and time-efficient methodology for the estimation of IBSD.
H. Shahriari; M. Honarmand; S. Mirzaei; A. Saffari
Abstract
This research work aims to discuss the methodology of using the drone-based data in the initial steps of the exploration program for the dimension stone deposits. A high-resolution imaging is performed by a low-cost commercial drone at the Emperador marble quarry, Kerman province, Iran. A ground resolution ...
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This research work aims to discuss the methodology of using the drone-based data in the initial steps of the exploration program for the dimension stone deposits. A high-resolution imaging is performed by a low-cost commercial drone at the Emperador marble quarry, Kerman province, Iran. A ground resolution of 3 cm/pix is achieved by imaging at an altitude of 70 m in order to ensure the precise lithological and structural mapping. An accuracy of less than 5 cm is promised for the 3D photogrammetric products. Hence, the flight is performed with an 80% front and a 70% lateral image overlap. Furthermore, 18 ground control points (GCPs) are used in order to meet the required accuracy. Photogrammetric processing is done by the Agisoft PhotoScan software. The geology map is prepared through the visual geo-interpretation of the orthophoto image. The faults and fractures are delineated using the high-resolution orthophoto and hill-shade model in the ArcGIS software. Accordingly, the density map of fractures is produced, and the deposit is divided into five structural zones. The 3D deposit model with an accuracy of 2.8 cm is reconstructed based on the digital elevation model (DEM). A primary block model is generated using the 3D deposit model in the Datamine software in order to determine the resource for each structural zone. Finally, considering the amount of resource and situation of fractures, the priority of exploration for developing activities and appropriate methods is defined for each structural zone. The research work results have convinced us to include drone-based imagery in the initial steps of dimension stone exploration to consume the time and cost of the operation.
