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The first borehole 5071_1_B of the ICDP‐Drilling the Ivrea‐Verbano zonE (DIVE) project in Italy, which intersects the Massone antiform, provides a unique opportunity to integrate downhole geophysical measurements with observations from 100% recovered drill core in rarely drilled lithologies. The objective of this study is to petrophysically and structurally characterize the rock mass and constrain factors influencing the seismic velocity in the lower continental crust. A comprehensive data set, comprising core, well log and vertical seismic profiling data, was collected. The structural analysis indicates that the axial plane of the intersected tightly folded antiform is slightly tilted at the borehole location and thus the borehole intersects the hinge zone at the top and its limb in the lower part of 5071_1_B. Numerous open natural fractures with variable dips and two dominant dip azimuthal orientations are identified along the borehole, which affect the electrical and acoustic properties. The velocities at the core, well log and seismic scale are consistent but lower than intrinsic seismic velocities of the lower continental crust, since they are not only affected by fractures but also by micro cracks at the 5071_1_B in situ conditions. A systematic lithology correlation is not evident for these properties. However, a cluster analysis of gamma ray and magnetic susceptibility logs shows an excellent agreement with the logged core lithologies in the presence of remarkable spatial variability. Furthermore, the main lithologies are grouped into three distinct clusters, suggesting two types of kinzigites with distinct magnetic and radiogenic properties. Plain Language Summary: The first borehole 5071_1_B of the ICDP‐Drilling the Ivrea‐Verbano zone (DIVE) project in Italy, which intersects a prominent fold structure, provides a unique opportunity to integrate downhole geophysical measurements with observations from 100% recovered drill core in rarely drilled rock types. This study aims to characterize the structural properties and rock types encountered in 5071_1_B as well as factors that influence seismic velocity in the lower continental crust. The structural analysis shows that the axis of the fold is tilted at the borehole location. This means that the borehole intersects its hinge zone at the top and its limb in the lower part of 5071_1_B. Many open fractures are found with different dip angles and two main orientations. These fractures affect the electrical and acoustic properties. Gamma ray and magnetic susceptibility logs are used in a geostatistical analysis to identify different rock types. The results match the rock types identified on the drill cores very well. The P‐ and S‐wave velocities at the core, well log and seismic scale are consistent but lower than the velocities of the lower continental crust at great depth. This is because they are affected by fractures and microcracks at the 5071_1_B pressure conditions. Key Points: The axial plane of the Massone antiform dips a few degrees to the west‐northwest in the vicinity of the borehole 5071_1_BThe cluster analysis of gamma and magnetic susceptibility logs agrees well with core lithologies given the notable spatial variabilityVelocities are consistent across the core, log and seismic scales, governed by brittle deformation and locally correlate with lithologies [ABSTRACT FROM AUTHOR]

Determining the mechanical characteristics of rocks is crucial in various civil engineering sectors. Traditionally, the mechanical properties of rocks are determined through on-site and laboratory tests carried out during geotechnical surveys. However, these extensive surveys require considerable time and resources. In contrast, hyperspectral remote sensing techniques offer a rapid and simple means to determine the mineral composition and crystallographic structure of rocks. These features, in turn, influence the rocks' mechanical properties. This study focuses on characterizing the mechanical properties of carbonate rocks in a laboratory setting, using hyperspectral sensors. Approximately 150 cylindrical carbonate rock samples, spanning a wide strength range, were collected from diverse Israeli rock outcrops. Employing a point spectrometer (0.4 to 2.5 µm) and a spectral image sensor (8.0 to 12.0 µm), we captured samples' light reflections and spectral emissivity. Mechanical attributes, including density, porosity, water absorption, and uniaxial compressive strength (UCS), were measured. Advanced data mining techniques identified statistical correlations between hyperspectral signatures and mechanical properties, pinpointing key wavelengths for prediction. The developed models exhibited excellent predictability for the specified properties, attributing accuracy to discernible mineralogy and internal crystalline structure through spectroscopy. However, predicting UCS showed slightly weaker results due to influences from internal flaws not entirely reflected in spectroscopic data. Nonetheless, outcomes regarding rock UCS were deemed satisfactory. These findings open avenues for non-destructive tools in assessing the mechanical properties of rocks in quarrying operations. Highlights: We developed a new method for evaluating the mechanical properties of carbonate rocks using non-destructive spectroscopy. We applied sophisticated data mining techniques to identify statistical correlations between the hyperspectral signatures and mechanical properties of rock samples. We found the key wavelengths for predicting density, porosity, water absorption, and uniaxial compressive strength of the rock samples. The ability to assess the mechanical properties of intact rocks through remote sensing can improve the fieldwork of an engineering geologist. [ABSTRACT FROM AUTHOR]

Rockfall phenomena are considered highly dangerous due to their rapid evolution and difficult prediction without applying preventive monitoring and mitigation actions. This research investigates a hazardous site in the Municipality of Vecchiano (Province of Pisa, Italy), characterized by vertical rock walls prone to instability due to heavy fracturing and karst phenomena. The presence of anthropical structures and a public road at the bottom of the slopes increases the vulnerability of the site and the site's risk. To create a comprehensive geological model of the area, Unmanned Aircraft System (UAS) photogrammetric surveys were conducted to create a 3D model useful in photointerpretation. In accessible and safe areas for personnel, engineering–geological surveys were carried out to characterize the rock mass and to define the portion of rock walls to be monitored. Results from nine multitemporal Robotic Total Station (RTS) measurement campaigns show that no monitoring prisms recorded significant displacement trends, both on the horizontal and vertical plane and in differential slope distance. Additionally, satellite Persistent Scatterer Interferometry (PSI) analysis indicates that the slopes were stable over the two years of study. The integration of these analysis techniques has proven to be an efficient solution for assessing slope stability in this specific rockfall-prone area. [ABSTRACT FROM AUTHOR]

Technological advancements have made rock engineering more data-driven, leading to increased use of machine learning (ML). While the use of ML in rock engineering has the potential to transform the industry, several methodological issues should first be addressed: (i) rock engineering's use of biased (poor quality) data, resulting in biased ML models and (ii) limited rock mass classification and characterization data. If these issues are not addressed, rock engineering risks using unreliable ML models that can have potential real-life adverse impacts. This paper aims to provide an overview of these methodological issues and demonstrate their impact on the reliability of ML models using surrogate models. To take full advantage of the benefits of ML, rock engineers should make sure that their ML models are reliable by ensuring that there are sufficient unbiased data to develop reliable ML models. In the context of this paper, the term sufficient retains a relative meaning since the amount of data that is sufficient to develop reliable a ML models depends on the problem under consideration and the application of the ML model (e.g., pre-feasibility, feasibility, design stage). [ABSTRACT FROM AUTHOR]

Ischia (Southern Italy) is a volcanic island of the Phlegrean Volcanic District that was historically affected by multiple geological hazards, including floodings, landslides, rockfalls, and earthquakes. In this study, rockfall stability is analysed with an integrated approach aimed at investigating the rockfall source, the propagation, and the deposition areas. The case study is represented by two outcrops over a 400-m-wide cliff made of Green Tuff and located on the western area of Mt. Epomeo. They are respectively located at 280 and 420 m a.s.l., just uphill the village of Frassitelli, Forio d’Ischia, which is an area of high residential, tourist, and agricultural importance. We analysed the fracture systems of the tuff cliff to compute the kinematic analysis of the potential failure mechanisms and to perform numerical simulations of rockfall scenarios. Successively, numerical simulations of rockfall scenarios were computed based on the acquired structural information. This allowed us to identify the most hazardous scenarios based on the rock trajectories and the percentage of rock blocks affecting the urban area. The influence of the rock shape and volume on the rockfall trajectories was analysed. In the most likely scenarios, we observed that 15–25% of the rock blocks bypass the geomorphological barriers and reach the urban area, with kinetic energy values spanning between 102 and 104 kJ. Such detailed rockfall hazard analysis allowed the definition of the mitigation interventions necessary for the protection of the nearby residential area. [ABSTRACT FROM AUTHOR]

Mudurnu County, situated in northwestern Turkey, is a prominent settlement area because it is located on major trade routes (i.e., the Silk Road and the Crimean Road) and has served as a trading town and a military base in the Byzantine, Seljuk, and Ottoman periods. Mudurnu County is affected by regional complex rock slope instabilities that pose a substantial hazard to the settlement area and generate regional risk to human life, buildings, houses, and industrial facilities. Mudurnu, because of its invaluable historical structures, has been nominated for the UNESCO World Heritage List. Yet, those historical structures are threatened by the rock instabilities. The aim of the paper is to characterize the rock mass on the western slopes of the Mudurnu Valley, through geomechanical evaluation of the rock and empirical assessment of the slope instabilities. The engineering geological and geomechanical properties of the area were acquired via a 3D point cloud together with field scan-line surveys. The western slope of the Mudurnu Valley was divided into 11 geomechanically uniform sectors. Classification of the sectors using the SMR and Q-slope methods demonstrated that the rock mass was prone to complex planar, wedge, and toppling failures. Proper identification of such complex failures was performed using a decision tree methodology. Estimation of the probabilities of the complex failures was accomplished using empirical classifications and field observations. It was found that Sector 8 was the most critical for combined toppling and wedge failures, as well as toppling with a combination of planar and wedge failures. In addition, Sector 6 was the most critical for combined toppling and planar failures. [ABSTRACT FROM AUTHOR]

Stope design is an important part of mine planning, and it aims to balance ore recovery, ore dilution, and production costs without compromising the safety aspects. This paper summarizes the main results from the research, which aims to introduce new techniques to describe the ore body and surrounding rock mass at the tunnel face prior to stope excavation. The research comprises a literature review and a survey among mining professionals to assess current stope design practices. The study identifies geotechnical data, software improvements, and integration of design into mine planning as the most critical areas for improvement. The empirical part of the study proposes new techniques for fast data acquisition. The laser-induced breakdown spectrometry (LIBS) technique is developed for measurements at the tunnel face and from core boxes to provide mineralogical and geometallurgical data. Ground-penetrating radar (GPR) studies are conducted to improve discontinuity characterization, and rapid photogrammetric methods are proposed for efficient tunnel geometry characterization. The techniques discussed in this paper already have many industrial applications. This study reveals their potential to be adopted and further developed to serve ore and rock mass characterization for stope design. [ABSTRACT FROM AUTHOR]

The assessment of landslide hazard related to slopes in fractured rock masses is generally correlated with the probability of occurrence of potential rockfall phenomena. The propensity to detachment of rock blocks can be defined through direct or indirect approaches. The first, widely used for decades, is regulated by the International Society for Rock Mechanics recommendations, and provides for the definition of a series of parameters for discontinuities that cross a line designated by the operator, according to the so-called “scanline” methodology. The most applied indirect approaches are based on the construction of a 3D model of the studied front through input data acquired by a digital camera, laser scanner or radar. These two different approaches were used to analyze the discontinuities orientation of a rocky slope on the west side of Mt. Pellegrino (northern Sicily). In this context, it is essential to anticipate rockfall, given the presence of densely urbanized areas at the foot of the rocky slope. The main discontinuity sets were obtained from traditional geo-structural analysis and 3D Point Cloud model of the slope; the latter were derived by applying the Structure from Motion technique on frames captured during the surveys. The kinematic analysis applied to the obtained data allowed us to define from a geomechanical perspective, the main modes of failure. Moreover, back analyses were carried out on the already collapsed blocks to reveal the most likely rockfall volume and reached distance. [ABSTRACT FROM AUTHOR]

In heterogeneous and fractured rock masses, joints are the most important elements controlling the hydraulic conductivity. Joints parameters are therefore crucial for estimating transport of mass and energy in many technical problems (e.g., slope stability, tunnels, geothermal and oil and gas studies). Hydraulic conductivity conceptual models follow well understood generalizations, but their quantitative estimation is not simple. Both laboratory and field tests have many limitations due to representativeness and scale effects. This study proposes a methodology for a preliminary hydraulic conductivity estimation in fractured and/or heterogeneous rock masses through a combination of in-situ geomechanical and geophysical measurements. Contact and no-contact geomechanical surveys were coupled with electric resistivity topographies in two selected test sites within a Mexican geothermal area in the framework of the Ge-Mex H2020 project. The test sites are representative of two different geological settings: a faulted rock mass with expected high hydraulic conductivity in proximity of the faulted areas and an abandoned marble quarry, with very good mechanical characteristics and negligible degree of fracturing. Moreover, both of them are located in remote areas with limited accessibility, in which rapid, time and cost-effective procedures are welcomed and recommended. The preliminary findings of this study were promising: estimated hydraulic conductivities were compared with independent laboratory measurements performed by other researchers showing a good correspondence and reliability. The proposed methodology demonstrated its reliability in decision making, in the technical support and its economical applicability also in similar difficult logistic situations. Article Highlights: A combination of in-situ geomechanical and geophysical measurements was adopted for a preliminary hydraulic conductivity estimation; Obtained field data were compared with independent laboratory estimations to assess the reliability of the proposed approach and compare representativeness and scale effects; Even given the difficult logistic conditions and the limitations of the available comparisons the proposed methodology demonstrated its reliability in decision making. [ABSTRACT FROM AUTHOR]

This work describes a procedure for building a high-quality 3D model of a rocky pinnacle in the Dolomites, Italy, using Structure from Motion (SfM) techniques. The pinnacle, known as "Campanile di Val Montanaia", is challenging to survey due to its high elevation and sub-vertical cliffs. The construction of the 3D model is the first step in a multi-disciplinary approach to characterize the rock mass and understand its behavior and evolution. This paper discusses the surveying operations, which involved climbing the pinnacle to collect Ground Control Points (GCPs) and using a UAV to capture aerial imagery. The photographs were processed using SfM software to generate point clouds, mesh, and texture, which were then used for rock mass discontinuity mapping. The study compares models of different qualities and point densities to determine the optimal trade-off between processing time and accuracy in terms of discontinuity mapping. The results show that higher quality models allow for more detailed mapping of discontinuities, with some drawbacks due to noise in the case of the densest solution (e.g., increase in frequency of outliers across the point cloud). These pros and cons are also discussed in relation to the computational cost necessary to build the models. The study also examines the limitations and challenges of performing discontinuity mapping in the different models, including subjectivity in interpretation. A further element of interest is the publication of a high-quality 3D georeferenced model of the "Campanile di Val Montanaia" to be used for several potential further applications, such as stability analyses and numerical modeling. [ABSTRACT FROM AUTHOR]

Proximity remote sensing techniques, both land- and drone-based, allow for a significant improvement of the quality and quantity of raw data employed in the analysis of rockfall phenomena. In particular, the large amount of data these techniques can provide allows for the use of probabilistic approaches to rock mass characterization, with particular reference to block volume and shape definition. These, in return, are key parameters required for a proper rockfall hazard assessment and the optimization of countermeasures design. This study aims at providing a sort of guide, starting from the data gathering phase to the processing, up to the implementation of the outputs in a probabilistic-based scenario, which is able to associate a probability of not being exceeded with total kinetic energy values. By doing so, we were able to introduce a new approach for the choice of design parameters and the evaluation of the effectiveness of mitigation techniques. For this purpose, a suitable case study located in Varaita Valley (Cuneo, Italy) has been selected. The area has been surveyed, and a model of the slope and a digital model of the rock faces have been defined. The results show that a 6.5 m3 block has a probability of not being exceeded of 75%; subsequent simulations show that the level of kinetic energy involved in such a rockfall is extremely high. Some mitigation techniques are discussed. [ABSTRACT FROM AUTHOR]

Over the past two decades, advances in remote sensing methods and technology have enabled larger and more sophisticated datasets to be collected. Due to these advances, the need to effectively and efficiently communicate and visualize data is becoming increasingly important. We demonstrate that the use of mixed- (MR) and virtual reality (VR) systems has provided very promising results, allowing the visualization of complex datasets with unprecedented levels of detail and user experience. However, as of today, such visualization techniques have been largely used for communication purposes, and limited applications have been developed to allow for data processing and collection, particularly within the engineering–geology field. In this paper, we demonstrate the potential use of MR and VR not only for the visualization of multi-sensor remote sensing data but also for the collection and analysis of geological data. In this paper, we present a conceptual workflow showing the approach used for the processing of remote sensing datasets and the subsequent visualization using MR and VR headsets. We demonstrate the use of computer applications built in-house to visualize datasets and numerical modelling results, and to perform rock core logging (XRCoreShack) and rock mass characterization (EasyMineXR). While important limitations still exist in terms of hardware capabilities, portability, and accessibility, the expected technological advances and cost reduction will ensure this technology forms a standard mapping and data analysis tool for future engineers and geoscientists. [ABSTRACT FROM AUTHOR]

A fracture network consists of individual fractures within a defined volume. The degree of connectivity observed in a volumetric sample from a discrete fracture network (DFN) is dependent on fracture intensity and sample size. If small enough, most volumetric samples from any DFN will be unfractured and, if relatively large, samples from a DFN will contain multiple, connected fractures. The sample size where fractured samples transition to unfractured samples is observed in this work to propose a characteristic fractured volume (CFV). The CFV is the size of a random sample that contains at least one fracture and is most likely to contain the equivalent cumulative fracture surface area of no more than one fracture. It is an emergent property of a DFN model that demonstrates connectivity of a fracture network. For this research, a series of eight DFN models were parameterized to consider the sensitivity of fracture intensity, orientation dispersion, and fracture size distribution to the observed CFV. These models were assessed by sequential spatial discretization with progressively smaller sub-volumes. The fracture intensity of each sample was calculated and categorized as unfractured, fractured, or intersected, based on predefined volumetric intensity thresholds. The coefficient of variation (CV%) was determined for each discretization size to consider variability of fracture intensity within sample sets. Sensitivity of the CFV size was observed for fracture intensity and fracture size distribution and not for orientation dispersion. For each DFN, the CFV was equivalent to the sample size with a measured CV% of 1. The potential of a relationship between CV% and CFV will allow for estimation of CFV from limited data and has potential for applications in geotechnical design. The CFV serves as a useful tool for DFN model validation. [ABSTRACT FROM AUTHOR]

A discrete fracture network (DFN) model based on non-parametric kernel density estimators (KDE) and directional-linear statistics is developed. The model provides a characterization of the fracture network with distributions of fracture orientation and size jointly. A solution to the Bertrand paradox is used for the calculation of disk sizes from trace lengths, the latter calculated from the intersection of disks and highwall faces by triangulation. A Poisson point process is applied for the generation of the model, with fractures assumed to be flat and circular in shape, the number of fractures per unit volume (P30) adjusted to match the experimental length of fractures per unit area (P21). Length censoring of traces due to the surface dimension is considered in the calculations by including semi-bounded traces, i.e., traces censored in one of their ends. Orientation and size biases are corrected with a weighting function in the random sampling. The truncation effect whereby no traces shorter than some cut-off length are recorded, is addressed by a randomized optimization algorithm. The joint fracture orientation-size distribution model developed is tested with trace maps of discontinuities measured from photogrammetric models of twelve highwall faces of quarry benches, with outstanding results. Computational advantages over traditional parametric fracture models are addressed. Highlights: Nonparametric directional-linear statistics has been used for the construction of DFN models. The mathematical analysis of this new approach is described in detail. A new link between distributions of disc size and pseudo-trace lengths is established. Relationships between means and variances for the distributions of trace length and disc size are discussed. Censoring bias is corrected by a mixed random variable and truncation bias is corrected by including semibounded traces and using a probabilistic filter. The nonparametric DFN model developed is applied to photogrammetric discontinuity data maps. Consistency of the results is assessed and thoroughly discussed. [ABSTRACT FROM AUTHOR]

Structure-from-Motion Multi-View Stereo (SfM-MVS) photogrammetry is a viable method to digitize underground spaces for inspection, documentation, or remote mapping. However, the conventional image acquisition process can be laborious and time-consuming. Previous studies confirmed that the acquisition time can be reduced when using a 360-degree camera to capture the images. This paper demonstrates a method for rapid photogrammetric reconstruction of tunnels using a 360-degree camera. The method is demonstrated in a field test executed in a tunnel section of the Underground Research Laboratory of Aalto University in Espoo, Finland. A 10 m-long tunnel section with exposed rock was photographed using the 360-degree camera from 27 locations and a 3D model was reconstructed using SfM-MVS photogrammetry. The resulting model was then compared with a reference laser scan and a more conventional digital single-lens reflex (DSLR) camera-based model. Image acquisition with a 360-degree camera was 3× faster than with a conventional DSLR camera and the workflow was easier and less prone to errors. The 360-degree camera-based model achieved a 0.0046 m distance accuracy error compared to the reference laser scan. In addition, the orientation of discontinuities was measured remotely from the 3D model and the digitally obtained values matched the manual compass measurements of the sub-vertical fracture sets, with an average error of 2–5°. [ABSTRACT FROM AUTHOR]

Geotechnical issues due to inappropriate support designs of underground drift will affect mining developments and production. The aim of this study was to provide a systematic support design method for deep hard-rock drifts in China. Field investigations and laboratory studies were carried out on the engineering geological properties of the rock masses along drifts in the Sanshandao Gold Mine. Potential wedge analysis and safety factors were determined using Unwedge software. The rock mass properties and support requirements were analyzed accordingly using different rock mass classification systems; then, an updated combined support system including rock bolts, wire mesh, and shotcrete was proposed. Numerical methods were used to quantify the plastic zone and principal stress of the drift, the plastic zone was reduced, and the rock stress state was improved after installing the support systems. Field monitoring data also confirmed that the updated support system prevented excessive rock mass deformation in drift. This study provides a reliable method for deep hard-rock drift support at Sanshandao Gold Mine and will also be helpful for the optimization of subsequent support. [ABSTRACT FROM AUTHOR]

This study wants to give a contribution to the semi-automatic evaluation of rock mass discontinuities, orientation and spacing, as important parameters used in Engineering. In complex and inaccessible study areas, a traditional geological survey is hard to conduct, therefore, remote sensing techniques have proven to be a very useful tool for discontinuity analysis. However, critical expert judgment is necessary to make reliable analyses. For this reason, the open-source Python tool named DCS (Discontinuities Classification and Spacing) was developed to manage point cloud data. The tool is written in Python and is based on semi-supervised clustering. By this approach the users can: (a) estimate the number of discontinuity sets (here referred to as "clusters") using the Error Sum of Squares (SSE) method and the K-means algorithm; (b) evaluate step by step the quality of the classification visualizing the stereonet and the scatterplot of dip vs. dip direction from the clustering; (c) supervise the clustering procedure through a manual initialization of centroids; (d) calculate the normal spacing. In contrast to other algorithms available in the literature, the DCS method does not require complex parameters as inputs for the classification and permits the users to supervise the procedure at each step. The DCS approach was tested on the steep coastal cliff of Ancona town (Italy), called the Cardeto–Passetto cliff, which is characterized by a complex fracturing and is largely affected by rockfall phenomena. The results of discontinuity orientation were validated with the field survey and compared with the ones of the FACETS plug-in of CloudCompare. In addition, the algorithm was tested and validated on regular surfaces of an anthropic wall located at the bottom of the cliff. Eventually, a kinematic analysis of rock slope stability was performed, discussing the advantages and limitations of the methods considered and making fundamental considerations on their use. [ABSTRACT FROM AUTHOR]

Rock mass characterization is the cornerstone of informed engineering analysis and design. Consequently, it is imperative to have access to quality data and understand the implications of mischaracterization and uncertainty of collected geotechnical data. This paper presents the results of an investigation on the influence of alteration on the mechanical properties of a rock mass. Field data from an underground hard rock mine illustrated that variations in type, fabric and intensity of alteration had a significant influence the rock mass strength as reported by point load testing. An analysis of alteration data systematically collected from core logging provided valuable insights on the impact of alteration on the strength anisotropy of the rock mass. The spatial distribution of foliation planes and the type, fabric and intensity of alteration varies significantly in the mine. The impact of alteration on rock mass strength contributed to areas of high convergence and high seismicity during mining. [ABSTRACT FROM AUTHOR]

The InfraRed Thermography (IRT) technique is gaining increasing popularity in the geosciences. Although several studies on the use of this technique for rock mass characterization were reported in the literature, its applicability is challenging in complex environments, characterized by poor accessibility, lithological heterogeneity, karst features and disturbances, such as vegetation and human activities. This paper reports the results of specific tests carried out to explore the application of IRT methods, supported by UAV surveys, for rock mass characterization in complex conditions. In detail, a 24-h monitoring was performed on an appropriate case study to assess which type of information can be collected and what issues can be expected. The results of the thermograms were compared with data reported in the literature and discussed. A novel method to detect correlations between the temperature profiles at the air-rock interfaces and the rock mass properties is presented. The main advantages, limitations and suggestions in order to take full advantage of the IRT technique in complex conditions are reported in the final section. [ABSTRACT FROM AUTHOR]

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In this paper, the slope rock mass is numerically characterized by considering hydraulic and mechanical properties using two distinct element models. The flow rate and permeability are calculated from localized fluxes through rock masses with varied fracture orientations and scales. Flow models suggest that rock mass permeability is predominantly controlled by fracture size. High rock mass permeability is simulated when the fractures are enlarged. Hydraulic anisotropy is captured when the difference in the fracture size is amplified. The mechanical properties of the slope rock mass are characterized through numerical shearing tests. In general, high permeability corresponds to low shearing resistance of the rock mass. The fractures obliquely distributed to shearing direction lead to additional shearing resistance. Enlarged fractures reflect high conductivity of the rock mass structure and decrease the shearing resistance. Mechanical anisotropy of the rock mass is also captured and attributed to the difference in the fracture size. The relations between hydraulic and mechanical properties are examined, and negative exponential relations are fitted between rock mass cohesion and permeability. The research introduces permeability as reference to slope rock mass characterization and provides reliable methods to this challenging issue. [ABSTRACT FROM AUTHOR]

Rock mass classification systems are used to categorize and estimate the role of the most significant parameters influencing rock mass behavior to represent an equivalent continuum. Generally, in these methods, the impact of the related parameters is considered uniform in all directions. Hence, these systems describe the rock mass as an isotropic medium. In some cases, in particular, for layered strata and systematically fractured rocks, the assumption of isotropic behavior may not provide realistic results. Hence, in this paper, to characterize the rock mass anisotropy, a directional rock mass rating (DRMR) has been proposed based on the well-known rock mass rating (RMR). So, DRMR provides a three-dimensional rock mass rating, quantitatively. By means of statistical distribution of DRMR, a classification for the degree of anisotropy of rock mass has been proposed. Furthermore, a criterion to identify the prominent rock mass, isotropic/transversely isotropic/anisotropic situation, is presented. Then the stereonet has been used to demonstrate an all-round graphical representation of DRMR. This with DRMR provides an illustrative insight into the actual rock mass condition and can assist to select the appropriate method for further analysis. Also, the method can be used as a basis to develop practical solutions for many rock engineering issues, such as characterizing the mechanical parameters of rock mass as an anisotropic equivalent continuum, selective directional rock mass improvement, and proper selection of rock tunnel and rock cavern alignments. Finally, the results of some practical applications of the method, based on field data, are presented. [ABSTRACT FROM AUTHOR]

The in situ block size distribution is an essential characteristic of fractured rock masses and impacts the assessment of rockfall hazards and other fields of rock mechanics. The block size distribution can be estimated rather easily for fully persistent fractures, but it is a challenge to determine this parameter when non-persistent fractures in a rock mass should be considered. In many approaches, the block size distribution is estimated by assuming that the fractures are fully persistent, resulting in an underestimation of the block sizes for many fracture geometries. In addition, the block size distribution is influenced by intact rock bridge failure, especially in rock masses with non-persistent fractures, either in a short-term perspective during a slope failure event when the rock mass increasingly disintegrates or in a long-term view when the rock mass progressively weakens. The quantification of intact rock bridge failure in a rock mass is highly complex, comprising fracture coalescence and crack growth driven by time-dependent changes of the in situ stresses due to thermal, freezing-thawing, and pore water pressure fluctuations. This contribution presents stochastic analyses of the two-dimensional in situ block area distribution and the mean block area of non-persistent fracture networks. The applied 2D discrete fracture network approach takes into account the potential failure of intact rock bridges based on a pre-defined threshold length and relies on input parameters that can be easily measured in the field by classical discontinuity mapping methods (e.g., scanline mapping). In addition, on the basis of these discrete fracture network analyses, an empirical relationship was determined between (i) the mean block area for persistent fractures, (ii) the mean block area for non-persistent fractures, and (iii) the mean interconnectivity factor. The further adaptation of this 2D approach to 3D block geometries is discussed on the basis of general considerations. The calculations carried out in this contribution highlight the large impact of non-persistent fractures and intact rock bridge failure for rock mass characterization, e.g., rockfall assessment. [ABSTRACT FROM AUTHOR]

In tunnelling, rock mass support is designed based on the observed rock mass conditions. These conditions are determined by rock mass characterization. Measurement while drilling (MWD), one such characterization method, acquires drill parameter data during drilling. These data can be used to predict rock mass conditions ahead of the face. In this study, grout-hole MWD data are collected at one of the main tunnels in the large infrastructural project Stockholm bypass tunnels. The normalized and filtered MWD data are correlated to the rock mass characteristics using multilinear regression and the Levenberg-Marquardt method. Although a strong numerical correlation cannot be obtained, the results are promising. As a result, a holistic visual approach, which linked the MWD parameters with the rock mass classification and rock support requirements, was developed. [ABSTRACT FROM AUTHOR]

The trend today to ever increasing modelling sophistication demands that much more attention be paid by practitioners to achieving better appreciation and characterization of geology and rockmass variability, so that rock–structure interaction effects can be analysed more realistically in better calibrated models. This paper is thus directed towards focussing attention on risk-based geological characterization as basis for helping modellers and designers improve calibration of their models. A sequential approach of appropriate input parameter refinement is outlined as a path forward methodology for consistently achieving maximum reliability in modelling. Processes that are needed for identifying key controlling geological structural features and rockmass domain characteristics that may be critical influences on true rockmass behaviour are explored so that rationalization steps can be followed in model building to ensure that actual behaviour drivers are not only properly represented, but are reliably characterized through rigorous calibration. Suggestions for the use of the observational and quantitative GSI charts at various scales appropriate to specific geological domains are presented as a means for achieving such calibration. Illustration is then given of how quantification can be achieved of rock quality variability throughout the complete range of rock competence, from intact pseudo-homogeneous high strength rockmasses subject to brittle spalling, through blocky, folded or foliated rockmasses, where kinematic controls are typically of paramount importance, through to completely degraded, fault process core zones and saprolites, where material matrix strength almost entirely dominates behaviour. Guidelines are given for suggested ranges of classification applicability for use with the Hoek–Brown failure criterion. [ABSTRACT FROM AUTHOR]

Rockfalls are one of the most dominant geological hazards in mountainous rocky regions with the potential to turn catastrophic if they occur in an anthropogenic environment. Therefore, the identification of potential rockfall locations is of high importance. Susceptibility is the magnitude that describes these locations and its qualitative and quantitative assessment is necessary for the timely treatment of potential events. Quantitative susceptibility assessment can be conducted using either data-driven methods such as bivariate and multivariate statistics as well as artificial neural networks or numerical methods such as static and dynamic models. In both approaches mathematical assumptions have to be made concerning the predisposing factors distribution and so there is an inherent need to achieve the higher possible confidence level in the input data. Such high-resolution data can be acquired using light detection and ranging (LiDAR) scanners. In the current study, LiDAR technology was implemented, and the data processing technique is analyzed step by step providing the reader with a view of the whole procedure. The results produced by the current methodology are validated and interpreted according to in situ measurements and observations based on unmanned aerial vehicle imagery. Post data processing, joint orientation, joint spacing and potential block volumes were extracted considering both persistent and non-persistent joints. The proposed methodology provides the creation of detailed high-resolution spatial distribution maps of the previously mentioned parameters, considering the variability of their values along the slope. The results can be used in a space-resolved susceptibility assessment providing higher-resolution input data for the subsequent susceptibility analysis. [ABSTRACT FROM AUTHOR]

Rock mass characterization is important to identify the condition of rock especially in major infrastructure like a tunnel. Rock mass characterization can be done either before, during or after construction completed. In this case study, this characterization was done after almost 20 years of tunnel operation. Characterization could not be done directly to the field as half of the rock mass along tunnel was covered by shotcrete layer. To overcome this problem, three integration methods which are field mapping, satellite image interpretation and geoelectrical tomography resistivity survey been approached. Satellite image interpretation is to emphasise negative lineament structure tracing while field mapping is to emphasis the location of groundwater intrusion and major tectonic structures like fault, joint and shear zone. Geoelectrical tomography resistivity survey was conducted using ABEM SAS 400 system and dipole-dipole array while raw data were processed using Res2DINV software. Data analysis showed three difference resistivity values which are high resistivity (> 1500 O.m), moderate (100-500 O.m) and low (<25 O.m). Findings from field mapping and lineament interpretation were used to interpret pseudosection. All three resistivity values were interpreted as high water content zone (low resistivity), lineament effected and highly fractured granitic rock mass (moderate resistivity) and low fractured granitic rock (high resistivity). [ABSTRACT FROM AUTHOR]

Probabilistic methods are the most efficient methods to account for different types of uncertainties encountered in the estimated rock properties required for the stability analysis of rock slopes and tunnels. These methods require estimation of various parameters of probability distributions like mean, standard deviation (SD) and distributions types of rock properties, which requires large amount of data from laboratory and field investigations. However, in rock mechanics, the data available on rock properties for a project are often limited since the extents of projects are usually large and the test data are minimal due to cost constraints. Due to the unavailability of adequate test data, parameters (mean and SD) of probability distributions of rock properties themselves contain uncertainties. Since traditional reliability analysis uses these uncertain parameters (mean and SD) of probability distributions of rock properties, they may give incorrect estimation of the reliability of rock slope stability. This paper presents a method to overcome this limitation of traditional reliability analysis and outlines a new approach of rock mass characterization for the cases with limited data. This approach uses Sobol's global sensitivity analysis and bootstrap method coupled with augmented radial basis function based response surface. This method is capable of handling the uncertainties in the parameters (mean and SD) of probability distributions of rock properties and can include their effect in the stability estimates of rock slopes. The proposed method is more practical and efficient, since it considers uncertainty in the statistical parameters of most commonly and easily available rock properties, i.e. uniaxial compressive strength and Geological Strength Index. Further, computational effort involved in the reliability analysis of rock slopes of large dimensions is comparatively smaller in this method. Present study also demonstrates this method through reliability analysis of a large rock slope of an open pit gold mine in Karnataka region of India. Results are compared with the results from traditional reliability analysis to highlight the advantages of the proposed method. It is observed that uncertainties in probability distribution type and its parameters (mean and SD) of rock properties have considerable effect on the estimated reliability index of the rock slope and hence traditional reliability methods based on the parameters of probability distributions estimated using limited data can make incorrect estimation of rock slope stability. Further, stability of the rock slope determined from proposed approach based on bootstrap method is represented by confidence interval of reliability index instead of a fixed value of reliability index as in traditional methods, providing more realistic estimates of rock slope stability. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize the rock mass at Mount Rushmore National Memorial (MORU) and to evaluate the stability of the presidential sculptures. The sculptures are carved in granite, but quartzmica schist and minor outcrops of pegmatite are also present within the site area. We divided the MORU area into four "regions" to collect discontinuity data. Since the sculptures were not accessible during this study, we used light detection and ranging (LiDAR) data and Split-FX software to determine the orientations of both the discontinuities and the slopes on the sculptures. The rock mass characterization results, using both the Rock Mass Rating system and the Q-system, indicate the granite, schist, and pegmatite classify as fair to good rock. Kinematic analysis results indicate that the potential for planar, wedge, and toppling failures exists for various slopes on each of the sculptures. The factor of safety (FS) values against planar and wedge sliding, ignoring cohesion, range from 0.1 to 0.8 and from 0.2 to 1.3, respectively. Since failures have not been observed at the memorial, we back-calculated the amount of cohesion required to raise the FS values to >1. The backcalculation results show that both cohesion and friction contribute to stability of the sculptures. Using the Slide program, we performed an overall slope probabilistic analysis for the slopes on which the MORU sculptures are located. The analysis determines the mean factor of *Corresponding author email: ashakoor@kent.edu safety (FSM), reliability index (RI), and probability of failure (PF) for the slopes. For the static condition, the analysis resulted in FSM, RI, and PF values ranging from 3.3 to 4.5 percent, 3.3 to 7.8 percent, and 0 percent, respectively. With a seismic load coefficient of 0.14 applied to the slopes, the corresponding values were: 2.6 to 4.1 percent, 2.9 to 4.7 percent, and 0 percent. For both the static and seismic conditions, the results indicate that, overall, the slopes of the sculptures are stable. [ABSTRACT FROM AUTHOR]

In this paper, an improved rock mass characterization method is presented. This method used a quantified geological strength index (GSI) and synthetic rock mass (SRM) model based on a discrete fracture network (DFN) and bonded particle model. A quantitative method is initially introduced to assist in the use of the conventional GSI chart, employing the rock block volume as the quantitative factor. The block volume for a given DFN model is calculated by a volumetric joint count, which is defined as the number of fractures intersecting a cube with unit length. The peak strength and deformation modulus of the rock mass are estimated based on the derived GSI, and then selected as references to constrain mechanical parameters of joints in the SRM model. A parametric study shows a positive correlation between the joint stiffness/friction coefficient and both the peak strength and deformation modulus. The joint friction coefficients of 0.5, 1.0, and 1.5 are suggested to correspond to the surface quality of ‘FAIR’, ‘GOOD’, and ‘VERY GOOD’ in the GSI chart. An advantage of the SRM over the GSI lies in the characterization of the post-peak strain softening behavior. The numerical results show that lower joint stiffness and friction coefficient result in a more ductile post-peak behavior. Additional SRM models with varied joint distributions show the complexities of rock mass characterization, where the rock mass strength, modulus, and post-peak strain softening rate may vary significantly with only one aspect of distributions of the joints, such as intensity or diameter. Triaxial testing is also conducted, and the SRM peak strengths are compared with the Hoek-Brown strength criterion based on the GSI system. The strengths of the regular triaxial models show general convergence with the Hoek-Brown criterion, but the strengths of the true triaxial models are less than those of the regular triaxial models due to deviatoric confining stresses. Meanwhile, ductile post-peak behavior is generally simulated in the triaxial testing. Cracking models are finally investigated and presented, behaving as additional information to explain the changes in the rock mass strength and deformability with different confining stresses. The method presented in this paper is meant to help geologists and engineers to quantify the GSI for jointed rock mass, and characterize the rock mass modulus and strength. Meanwhile, the synthetic rock mass method provides an alternative for rock mass characterization in addition to the traditional GSI method. [ABSTRACT FROM AUTHOR]

Copyright of Geomechanik und Tunnelbau is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rock slope failure modes are either driven by structurally controlled mechanisms (planar, wedge, or toppling failure) or lean upon the highly jointed or weak rock mass (circular failure). Developing practical tools for preliminary slope design is a popular topic among geotechnical society. This study proposes a practical methodology to predict a safe overall slope angle for weak rock slopes of lignite mines. Rock mass rating (RMR) and slope mass rating (SMR) classification systems can be remarkably misleading for weak rocks. Fuzzy modification was proven to improve rock and slope quality predictions. In addition, structurally controlled failures can be estimated more precisely. Later, a popular slope performance chart of Bieniawski that is based on RMR was modified by the fuzzy approach, and the computer models of a weak rock mass failure in a Turkish lignite mine are presented. The modified methodology was proven to be better suited to the weak rock conditions. [ABSTRACT FROM AUTHOR]

A detailed understanding of the drilling system and the drilling control is required to correctly interpret rock mass conditions based on monitored drilling data. This paper analyses data from hydraulic in-the-hole (ITH) drills used in LKAB's Malmberget mine in Sweden. Drill parameters, including penetration rate, percussive pressure, feed pressure, and rotation pressure, are monitored in underground production holes. Calculated parameters, penetration rate variability, rotation pressure variability, and fracturing are included in the analysis to improve the opportunity to predict rock mass conditions. Principal component analysis (PCA) is used to address non-linearity and variable interactions. The results show that the data contain pronounced hole length-dependent trends, both linear and step-wise linear, for most parameters. It is also suggested that monitoring can be an efficient way to optimize target values for drill parameters, as demonstrated for feed force. Finally, principal component analysis can be used to transfer a number of drill parameters into single components with a more straightforward geomechanical meaning. [ABSTRACT FROM AUTHOR]

We investigate the relationships between the in situ P-wave velocity (Vp) of rock masses, measured by borehole acoustic logging, and their Geological Strength Index (GSI), to support a reliable assessment of equivalent continuum rock mass properties at depth. We quantified both Vp and GSI in three deep boreholes drilled in a crystalline core complex of the central Italian Alps. The boreholes were driven up to 400 m in depth and provided high-quality drill cores in gneiss, schist and metasedimentary rocks with variable lithology. Geological and geomechanical logging was carried out for over 800 m of cores, and acoustic logging was performed for more than 600 m of borehole length. High-resolution core logging in terms of GSI was obtained using an original quantitative approach. Candidate empirical correlation functions linking Vp and GSI were tested by a two-step statistical analysis of the experimental dataset, including outlier removal and nonlinear regression analysis. We propose a sigmoid Vp-GSI equation valid over a depth range between 100 and 400 m. This accounts for extremely variable lithological, weathering and rock mass damage conditions, complementing existing shallow-depth approaches and showing potential for practical applications in different engineering settings. [ABSTRACT FROM AUTHOR]

The 14.6 km long Istanbul Strait Road Crossing Project is a safe, quick and environmentally responsible alternative road link between Asia and Europe, as such it is being constructed under a Build-Operate-Transfer contract by a public-private partnership. The investor/contractor has committed to build the Project in 55 months and to operate the facility for a concession period of approximately 25 years. This article examines the project's two critical structures located in the Asian side of Istanbul, considering site investigation, construction and monitoring. The first structure is a cut and cover construction next to the Bosphorus, called the Asia Transition Box (ATB), which enabled the launching of the TBM and conventional tunnels. The second is the conventionally excavated twin tunnels (CETT), which pass under a highly urbanized part of Istanbul and provide the transition from the highway into the tunnel under the Bosphorus. [ABSTRACT FROM AUTHOR]

We describe a stability study for a tunnel excavated in a fractured rock mass. The proposed methodology uses automatic and semi-automatic algorithms to extract joint sets from a LIDAR point cloud. Using that information and considering a model of ubiquitous joints, pyramidal and non-pyramidal unstable blocks were identified using the keyblock method. The algorithms used for the stability analysis were implemented in BLOFOR software, which represented the possible location of the blocks in the tunnel in three dimensions and provided information on tunnel stability, including a safety factor for each block. [ABSTRACT FROM AUTHOR]

The Italian cultural heritage is one of the most noticeable in the world; an important part of it is subjected to natural hazard and risk conditions. Religious buildings, due to their location on impervious sites are particularly exposed to landslides. In this paper we study the hermitage of Cerbaiolo (Tuscany, central Italy). The hermitage, founded in the 8th century as a Benedictine monastery is now a Franciscan Women Institute seat. The buildings are on the edges of a limestone plate overlapped to a clayey formation. Falls, toppling and slides are present along the limits of the plate due to the geomechanics properties of the rock and to the contrast between the two lithological complexes. In order to identify the main joint sets affecting the rock mass a structural-geological survey was carried out and four sets are identified. The rock plate was classified according to Bieniawski, Barton and Geological Strength Index approaches. The outcomes confirm the predisposing factors to mass movements, corresponding to the intensity and characteristics of fracturing of the rock mass. With regard to the slope stability analysis, a failure mechanism involving sliding along a single plane (plane failure) was assumed on the first approximation. The analyses take into account the presence of tension cracks as an indicator factor for the instability phenomenon. The results of stability analyses, performed in static and seismic conditions, indicate a widespread instability condition. The dip slope direction, the properties and type of discontinuities and the local variation of composition influence the hazard assessment. [ABSTRACT FROM AUTHOR]

The article focuses on the quantitative measurements of fracture aperture and directional roughness from rock cores. It mentions that the spatial aperture distribution and roughness of fractures could have a significant influence on their hydromechanical behavior. The measurement of the spatial distribution of fracture aperture involves the measurement of the fracture surface topography.

Systematic rock mass characterization is an integral part of rock engineering practices. In the present scenario several classifications are in used for rock mass characterization for tunnelling. The present paper discusses engineering geological investigations carried out for Punasa tunnel, a part of Narmada Sagar project. The horse shoe shaped tunnel is 3675.25 m long and 9 m in diameter. This straight and free flow tunnel has been constructed in basaltic lava flows erupted during Cretaceous to Eocene age, belonging to poor to fair rock mass rating (RMR) and extremely poor to good in tunnel quality (Q-system). The values of RMR and Q-system ranges from 29 to 74 and 0.0825 to 13.33 respectively. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The castle, palaces and man-made historical and recent cave dwellings of Hasankeyf will be partly flooded by the reservoir of the Il&imath;su dam which is planned to be constructed over the Tigris River. Hasankeyf is entirely within the Germik formation which is composed of whitish to light gray and/or beige, medium strong, fresh to slightly weathered, thick to very thick bedded, locally massive, almost horizontal or gently dipping silty, sandy limestone. The major geotechnical concerns in the area consist of the possibility of kinematic failure of the foundation of "Little Palace" and the collapse of some of the roofs of the adjacent man-made cave dwellings carved in rock due to insufficient pillar (wall) thicknesses to carry the overburden load. A limit equilibrium analysis of the kinematically unstable planar rock block underlying the foundation of "Little Palace" was performed as a function of the water level in the reservoir. The maximum required anchor force was calculated as approximately 3,000 kN/m which led to a total anchor force of about 42,000 kN for the 14-m-wide slope face of the unstable planar block. The results of the finite element analysis to determine the minimum stable pillar (wall) thickness required between adjacent caves led to a recommendation to apply a steel arch support to one of the adjacent caves at Hasankeyf in case the wall thickness was less than or equal to 0.60 m. [ABSTRACT FROM AUTHOR]

The castle, palaces and man-made historical and recent cave dwellings of Hasankeyf will be partly flooded by the reservoir of the Ilısu dam which is planned to be constructed over the Tigris River. Hasankeyf is entirely within the Germik formation which is composed of whitish to light gray and/or beige, medium strong, fresh to slightly weathered, thick to very thick bedded, locally massive, almost horizontal or gently dipping silty, sandy limestone. The major geotechnical concerns in the area consist of the possibility of kinematic failure of the foundation of "Little Palace" and the collapse of some of the roofs of the adjacent man-made cave dwellings carved in rock due to insufficient pillar (wall) thicknesses to carry the overburden load. A limit equilibrium analysis of the kinematically unstable planar rock block underlying the foundation of "Little Palace" was performed as a function of the water level in the reservoir. The maximum required anchor force was calculated as approximately 3,000 kN/m which led to a total anchor force of about 42,000 kN for the 14-m-wide slope face of the unstable planar block. The results of the finite element analysis to determine the minimum stable pillar (wall) thickness required between adjacent caves led to a recommendation to apply a steel arch support to one of the adjacent caves at Hasankeyf in case the wall thickness was less than or equal to 0.60 m. [ABSTRACT FROM AUTHOR]

Quantitative characterization of discontinuities is fundamental to define the mechanical behavior of discontinuous rock masses. Several techniques for the semi-automatic and automatic extraction of discontinuities and their properties from raw or processed point clouds have been introduced in the literature to overcome the limits of conventional field surveys and improve data accuracy. However, most of these techniques do not allow characterizing flat or subvertical outcrops because planar surfaces are difficult to detect within point clouds in these circumstances, with the drawback of undersampling the data and providing inappropriate results. In this case, 2D analysis on the fracture traces are more appropriate. Nevertheless, to our knowledge, few methods to perform quantitative analyses on discontinuities from orthorectified photos are publicly available and do not provide a complete characterization. We implemented scanline and window sampling methods in a digital environment to characterize rock masses affected by discontinuities perpendicular to the bedding from trace maps, thus exploiting the potentiality of remote sensing techniques for subvertical and low-relief outcrops. The routine, named QDC-2D (Quantitative Discontinuity Characterization, 2D) was compiled in MATLAB by testing a synthetic dataset and a real case study, from which a high-resolution orthophoto was obtained by means of Structure from Motion technique. Starting from a trace map, the routine semi-automatically classifies the discontinuity sets and calculates their mean spacing, frequency, trace length, and persistence. The fracture network is characterized by means of trace length, intensity, and density estimators. The block volume and shape are also estimated by adding information on the third dimension. The results of the 2D analysis agree with the input used to produce the synthetic dataset and with the data collected in the field by means of conventional geostructural and geomechanical techniques, ensuring the procedure's reliability. The outcomes of the analysis were implemented in a Discrete Fracture Network model to evaluate their applicability for geomechanical modeling. [ABSTRACT FROM AUTHOR]

Rock slope failures in urban areas may represent a serious hazard for human life, as well as private and public property, even on the occasion of sporadic episodes. Prevention and mitigation measures indispensably require a proper rock mass characterization, which is often achieved by means of time-consuming, costly and dangerous field surveys. In the last decades, remote sensing devices such as high-resolution digital cameras, laser scanners and drones have been widely used as supplementary techniques for rock slope analysis and monitoring, especially in poorly accessible areas, or in sites of large extension. Although several methods for rock mass characterization by means of remote sensing techniques have been reported in specific studies, there are very few contributions that focused on comparing the different methods in an attempt to establish their advantages and limitations. With this study, we performed digital photogrammetry, Terrestrial Laser Scanning and Unmanned Aerial Vehicle surveys on a cliff located in a popular tourist attraction site, characterized by complex geological and geomorphological settings, as well as by disturbance elements such as vegetation and human activities. For each point cloud, we applied geostructural analysis by means of semi-automatic methods, and then compared multi-temporal acquisitions for cliff monitoring. By quantitative comparison of the results and validation by means of conventional geostructural field surveys, the pros and cons of each method were outlined in attempt to depict the conditions and goals the different techniques seem to be more suitable for. [ABSTRACT FROM AUTHOR]