Bordehore et al compare manual and remote sensing field discontinuity collection used in kinematic stability assessment of failed rock slopes. The study presented herein has highlighted that the ...combined analysis of discontinuity orientations obtained by manual procedures using a compass and from 3D point clouds enable a considerable increment in the quality of the stereograms produced, and therefore, of the orientations derived. One important advantage is that the combination of both methods improves representativeness of minority discontinuities or those with scarce dip measurements (e.g. Ji). These joint stats were previously under-represented due to accessibility difficulties for manual data collection with a compass. In this sense, the analyses carried out have highlighted that the slope failure studied by Jorda et al.28 occurred through the curve surface defined by S0 and J2, instead of S0 only. The "1 set, widely represented at the upper pan of the slope, is responsible for delimiting the failure in tension crack mode.
The Q-slope (2015) geomechanical classification is the only empirical methodology for slope stability analysis that considers the effect of ice. This article shows the results of its application for ...icy slopes in Spain. Despite its sunny image, Spain is a mountainous country with cold winters. Slopes alongside a mountain road and a ski resort carpark have been studied in Puerto de Navacerrada (Madrid region) and Benasque (Pyrenees). This work combines the manual collection of geomechanical data on slope characteristics with an empirical analysis of slope stability and remote data acquisition techniques (Structure from Motion, SfM). The results of the field data collection are shown in a metaverse with two approaches: a 360° image virtual tour and a 3D image repository. One of the novelties of this work is that researchers who wish to replicate these analyses can access a table of input parameters and make a virtual field trip to see the parameters included in this study. The results show that the Q-slope methodology is useful for stability analysis and is conservative in terms of recommendations: All the slopes that are seen as unstable appear as such, but some slopes that do not present problems are shown as “transitional” slopes. The data and observations taken are useful for increasing the methodology database and for completing existing graphs of stable vertical slopes with good quality, as well as slopes with little slope and low quality.
This paper is focused on the Middle Paleolithic rock shelter called “Abrigo de San Lázaro”, placed in the Eresma River valley (Segovia, Spain). In this area, a multisource geomatic approach is used. ...On the one hand, the external envelope of the shelter has been digitalized by the means of an efficient combination between aerial photogrammetry and laser scanning (static and mobile). On the other hand, the ground penetrating radar and the electric tomography were used with the aim of evaluating the inner disposition of the shelter. The combination of both digitalization (external and internal) has allowed for improving the knowledge of the site characteristics that, in turn, will facilitate the future excavation works. The results of these studies allow archaeologists to know new data for a better understanding of the site formation (geology of the site, sedimentary potential, rock shelter dimensions, etc.) and the events that took place in it (knowing its historical evolution, especially the interaction between man and the environment). Additionally, the information obtained from these studies is very useful to plan future excavation works on the site.
This manuscript presents a relevant practical application of the stability analysis of multi-face slopes that uses the concept of the restricted daylight envelope in multi-faced slopes (MFS). The ...methodology was applied to the back analysis of a case study of a failed slope in mudstones and sandstones on the Spondylus coast in Ecuador. The instabilities analyzed included several rock cliffs with dihedral rock faces in mudstones. It is interesting to analyze the failure mechanism of these natural coastal slopes because, on the Spondylus coast, several hotels and tourist spots are located near the upper parts of some similar regions. The stereographic projection methodology can simulate complex geometries and simplify the analysis.
Technological progress in remote sensing has enabled digital representation of terrain through new techniques (e.g. digital photogrammetry) and instruments (e.g. 3D laser scanners). However, the use ...of old aerial images remains important in geosciences to reconstruct past landforms and detect long-term topographic changes. Administrations have recently expressed growing interest in sharing photogrammetric datasets on public repositories, providing opportunities to exploit these resources and detect natural and anthropogenic topographic changes. The SfM-MVS photogrammetric technique was applied to scanned historical black and white aerial photos of the Serra de Fontcalent (Alicante, Spain), as well as to recent high-quality digital aerial photos. Ground control points (GCPs) extracted from a LiDAR-derived three-dimensional point cloud were used to georeference the results with non-linear deformations. Two point clouds obtained with SfM-MVS were compared with the LiDAR-derived reference point cloud. Based on the result, the quality of the models was analysed through the comparison of the stages on stable areas, i.e., lands where no variations were detected, and active areas, with quarries, new infrastructures, fillings, excavations or new buildings. This study also indicates that errors are higher for old aerial photos (up to 5 m on average) than recent digital photos (up to 0.5 m). The application of SfM-MVS to open access data generated 3D models that enhance the geomorphological analysis, compared to stereophotogrammetry, and effectively detected activities in quarries and building of landfills.
•Existing techniques enable the use of historical and recent aerial photos to reconstruct DEMS•An area of interest is reconstructed using historical printed and digital aerial photos, obtained from readily available resources, through Structure-from-Motion•An airbone LiDAR derived point cloud was used as a benchmark and for the extraction of ground control points•Three different stages of the landform were analysed and compared•The quality of the reconstruction and the capability of monitoring changes were analysed
The cavities or lava tubes in the Galapagos Islands were formed by the differential cooling of the basaltic flow of the volcanoes surrounding these islands. In this article, a stability analysis was ...carried out to determine the degree of safety of different lava tubes using three methods: two empirical ones based on geomechanical classifications and one strain–strain (Hoek–Brown failure criterion). The methodology used consisted of the following phases: (i) compilation of information based on existing geomechanical mapping; (ii) geomechanical classification of the rock mass using Barton’s Q index and rock mass rating; (iii) steady state qualification using the geotechnical index of cavities (GCI); (iv) numerical modeling applying the Hoek–Brown criterion; (v) comparison of methodology and discussion of the results. The data obtained indicate that the methodologies used to evaluate the stability of the lava tubes have high reliability since they allowed the characterization of the different lava tubes. As the final “product” of the investigation, a graph was drawn up in which the empirical observations and the safety factors obtained with the numerical analysis (stress–strain) were superimposed, classifying the lava tubes as stable and non-stable. It can be concluded that the characterization methodologies used in this article can be applied to similar cases and fill a gap in rapid preliminary analyses of the degree of stability and risk of cave collapse.
The 3D point clouds obtained from the low-cost, remote, and precise SfM (Structure from Motion) technique allow the extraction and acquisition of discontinuities and their characteristics both ...manually, with the compass and virtual ruler of the Cloud Compare software, and automatically with the DSE (Discontinuity Set Extractor) program, which is faster, more accurate, and safe. Some control plans have been used, which basically consist of identifying one or several fractures and taking measurements on them manually and remotely. The difference between both types of measurements is around 5°, which we believe is reasonable since it is within the precision and repeatability of measurements with a geologist’s compass. This work analyzes the stability of six slopes (five excavated and one natural) by applying five different analysis methodologies based on the rock mass classification system (SMR, RHRSmod, and Qslope), kinematic analysis, and analytical analysis (limit equilibrium). Their results were compared with what was observed in the field to identify the most appropriate analysis methodologies adjusted to reality. The necessary parameters for analyzing each of the slopes, such as orientation, quantity, spacing, and persistence of the discontinuities, were obtained from the automatic analysis. This type of analysis eliminates the subjectivity of the authors, although the findings are related and resemble those obtained manually. The main contribution of the article consists of the application of fast and low-cost techniques to the evaluation of slopes. It is a type of analysis that is in high demand today in many Andean countries, and this work aims to provide an answer. These methodologies suggested by scientific articles such as this one will later be integrated into some procedures and will be taken into account by technical reports. The results show that with the available information and by applying low-cost techniques, the SMR system is the methodology that presents the best results and adjusts better to the reality of the study area. Therefore, SMR is a necessary parameter to determine rockfall hazards through modified RHRS.
The structure and ice content of ice caves are poorly understood. Ground penetrating radar (GPR) can provide useful insights but has only rarely been applied to ice caves. This paper interprets GPR ...images (radargrams) in terms of internal structure, stratification, compaction, thickness and volume of the ice block in the Peña Castil ice cave (Central Massif of Picos de Europa, northern Spain), providing the endokarst geometry of the ice cave in GPR data reflections. Eight radargrams were obtained by applying a shielded ground‐coupled antenna with a nominal frequency of 400 MHz. Although the radargrams do not depict the ice–basal bedrock interface, they suggest that the ice block is at least 54 m deep and similarly thick. Some curved reflection signatures suggest a potential vertical displacement in the block of ice, and thus certain dynamics in the ice body. Other images show numerous interbedded clasts and thin sediment layers imaged as banded reflections. In this particular cave a direct visual inspection of the ice stratigraphy is a difficult task but GPR provides clear reflectivity patterns of some of its internal features, making GPR a suitable instrument for this and future studies to achieve a better and broader understanding of the internal behavior of ice caves.
The stability of many shallow caves and rock shelters relies heavily on understanding rock discontinuities, such as stratification, faults, and joints. Analyzing these discontinuities and determining ...their orientations and dispersion are crucial for assessing the overall stability of the cave or shelter. Traditionally, this analysis has been conducted manually using a compass with a clinometer, but it has certain limitations, as only fractures located in accessible areas like the lower part of cave walls and entrances are visible and can be assessed. Over the past decade, remote sensing techniques like LiDAR and photogrammetry have gained popularity in characterizing rocky massifs. These techniques provide 3D point clouds and high-resolution images of the cave or shelter walls and ceilings. With these data, it becomes possible to perform a three-dimensional reconstruction of the cavity and obtain important parameters of the discontinuities, such as orientation, spacing, persistence, or roughness. This paper presents a comparison between the geomechanical data obtained using the traditional manual procedures (compass readings in accessible zones) and a photogrammetric technique called Structure from Motion (SfM). The study was conducted in two caves, namely, the Reguerillo Cave (Madrid) and the Cova dos Mouros (Lugo), along with two rock shelters named Abrigo de San Lázaro and Abrigo del Molino (Segovia). The results of the study demonstrate an excellent correlation between the geomechanical parameters obtained from both methods. Indeed, the combination of traditional manual techniques and photogrammetry (SfM) offers significant advantages in developing a more comprehensive and realistic discontinuity census.
Puerto de Cajas serves as a vital high-altitude passage in Ecuador, connecting the coastal region to the city of Cuenca. The stability of this rocky massif is carefully managed through the assessment ...of blocks and discontinuities, ensuring safe travel. This study presents a novel approach, employing rapid and cost-effective methods to evaluate an unexplored area within the protected expanse of Cajas. Using terrestrial photogrammetry and strategically positioned geomechanical stations along the slopes, we generated a detailed point cloud capturing elusive terrain features. We have used terrestrial photogrammetry for digitalization of the slope. Validation of the collected data was achieved by comparing directional data from Cloud Compare software with manual readings using a digital compass integrated in a phone at control points. The analysis encompasses three slopes, employing the SMR, Q-slope, and kinematic methodologies. Results from the SMR system closely align with kinematic analysis, indicating satisfactory slope quality. Nonetheless, continued vigilance in stability control remains imperative for ensuring road safety and preserving the site's integrity. Moreover, this research lays the groundwork for the creation of a publicly accessible 3D repository, enhancing visualization capabilities through Google Virtual Reality. This initiative not only aids in replicating the findings but also facilitates access to an augmented reality environment, thereby fostering collaborative research endeavors.
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