All along this lecture we will argue the benefits of integrating structural geology into rock engineering. Despite ISRM’s recommendations, we will also expose the very low percentage of tunnelling or dam projects involving structural geologists and more generally the widespread lack of structural geology expertise in civil and rock engineering projects, its consequences and associated missed opportunities. Standard geological studies are usually not enough to provide adequate level of details and quantitative assessments but this can be done with structural geology which allows us for instance to link fractures’ geometry, stress conditions and hydraulic conductivity no matter the scale, from small (e.g. a tunnel face), to large (e.g. full site). We will provide a suite of concrete examples coming from real-world site investigations, from design to construction, in order to illustrate these major benefits of structural geology in rock engineering. Structural geology is too often reduced to the manual or remote measurement of fractures to elaborate stereonets and distinguish fracture sets, frequently without any overarching assessment of the structure of the site in question. Whilst the use of structural geology is widely accepted and developed in oil & gas industry, especially during investigatory studies, it is not so in civil and rock engineering projects. One explanation is that engineers struggle with geological observations and the establishment of a diagnostic based upon too few or incomplete sets of data. One way to overcome this challenge is to build multi-disciplinary teams with both structural geologists and rock engineers which brings a plurality of perspectives and complementary skillsets. However, hiring both structural geologists and rock engineers will usually increase costs which may explain why it is not often considered. More important, during the last decades there has been a real decline in structural geology university courses around the world, supplanted by “new” disciplines often linked to the environment, so that even when the need for structural geology is understood, geologists with the right training and skillset are not always available. Whilst the ISRM could be more vocal about its recommendation to use structural geology in industrial and research projects, it cannot on its own change our mindsets. Consequently, we argue that individuals also have a responsibility to promote and embed structural geology in all rock engineering projects, from industry to research projects. We show one way forward on how this can be done, on the job or at industry and academic events.

Discontinuity flow behaviour in fractured rock mass remains a challenge in rock mechanics. This is due to fluid path prediction and velocities through the unsaturated zone under changing moisture conditions. This study proposes using the rock engineering systems (RES) approach to examine the interaction of the principal parameters in assessing discontinuity flow behaviour in fractured rock. This is achieved by a soft approach 3×3 interaction matrix in which the leading diagonal of the matrix is partially saturated flow, discontinuities in the fractured rock mass and the application of infrared thermography and photogrammetry. A georeferenced photogrammetry model is employed for 3D geotechnical discontinuity feature extraction. The analysis of these interactions shows that partial saturation in fractured rock mass depends on the discreet fractures, fracture network connectivity and matrix influence on storage. The leading diagonals of this RES approach highlight the most critical parameters for partially saturated discontinuity flow behaviour in fractured rock.

Fluid flow shows different behaviors through rough fractures with different scales. Numerical study as a powerful tool can be used to simulate fluid flow through a fracture with different scales. Geometrical properties, such as physical aperture and roughness, are important factors that have to be measured precisely. Photogrammetry, as a high-precision technique, was hired to reconstruct three-dimensional (3D) model of a granite fracture with a dimension of 25 cm × 25 cm × 10 cm. A high number of markers and scale bars were used to scale and orient the 3D model of the fracture accurately. The obtained 3D model of the fracture was used to simulate fluid flow behavior in a rough rock fracture. To validate the numerical modeling, experimental hydraulic tests were conducted with different hydraulic gradients ranging from 20 (kPa/m) to 200 (kPa/m) with an interval of 20 (kPa/m) under 0.3 MPa normal stress condition. Then, the obtained 3D model was used to simulate fluid flow through the fracture in different side lengths of 5 cm, 10 cm, 15 cm, 20 cm and 25 cm with the same hydraulic gradients. The results showed that the relationship between the hydraulic gradient and the flow rate was nonlinear and followed the Forchheimer Equation. The obtained hydraulic apertures were normalized to the subsample size lengths and were compared together. The results show the normalized hydraulic aperture decreases by increasing the sample sizes.

The analysis of the stability of rock slopes requires studying both the rock mass and the discontinuities within it. Discontinuities are typically considered planar at a reduced scale of study, usually on the order of meters. Furthermore, they tend to occur in sets with similar orientations. The characterization of these sets decisively influences the stability of the rock slope, making their study a key component. Traditionally, manual methods (compass, clinometer, measuring tape, etc.) have been used to collect data on the rock mass. However, this data collection is subject to operator subjectivity, potential hazards from falls or rockfalls, or even weather conditions. In this regard, the use of remote sensing techniques such as terrestrial 3D laser scanning or digital photogrammetry with RPAS (Remotely Piloted Aircraft Systems) has acquired popularity and acceptance within the scientific community in the last decade. Terrestrial laser scanning (TLS) is highly accurate and has been extensively used to geometrically characterize slopes. However, this instrumentation has the limitation that measurements are taken at ground level. Some areas of the slope may not be observable from the ground, thus limiting the surface that can be scanned. The popularization and accessibility of RPAS have enabled their widespread use in digitizing rock slopes using Structure from Motion (SfM), allowing for the reconstruction of surfaces in areas that cannot be digitized with TLS. However, the accuracy of this technique is lower compared to TLS. This research proposes the digitization of slopes using RPAS and airborne 3D laser scanning, with a comparison to data acquired with TLS assuming that the TLS data is correct. The study involves obtaining families of discontinuities using both techniques, and the comparison will allow for a discussion on whether the achieved level of accuracy and resolution are sufficient for addressing the geometric study of the discontinuity families. Two case studies are presented in the province of Alicante, Spain, analyzing the discontinuities in subvertical Cretaceous marls and another outcrop of Alicante Miocene.

Discontinuities significantly impact the stability of a rock mass and its hydraulic conductivity. Therefore, mapping rock discontinuities is essential to study rock mass behavior. This study explores the use of videogrammetry for digitizing rock mass at the tunnel face and measurements of joint orientations. Utilizing a mobile device for video capture, the method is compared against traditional laser scanning and mobile photogrammetry. Videogrammetry allows rapid data collection with smartphones or action cameras, emphasizing low-cost and accessibility. Results indicate that videogrammetry with a smartphone pro-vides an acceptable level of 3D reconstruction, with 3 mm control distance error and 1 cm cloud-to-cloud distance compared to a reference high-resolution laser scan. Discontinuity orientations measured from the videogrammetric 3D model show reasonable errors of less than 2-6° on average compared to data measured from the reference laser scan. The study validates videogrammetry as a practical, efficient alternative for rock mass characteriza-tion in underground settings.

Locality Devils Town in Serbia hosts a rock formation constituting of weathered andesitic tephra deposits shaped by erosion into many bizarre landforms.Tephra layer comprises of homogeneous but poorly graded andesitic fragments ranging from pebble to boulder size, which are submerged into weathered volcaniclastic matrix. Through the years, erosion carved into loose material leaving more resilient parts to stand out. They appear as numerous closely spaced pillars, up to 15 m in height and a few meters across, commonly capped with a large andesitic boulder. The site is labeled as natural heritage and has been recently subjected to holistic monitoring projects, including non-invasive techniques such as terrestrial LiDAR, Structure from Motion and Photogrammetry. These have provided several sequences of point clouds, allowing change analysis to take place. Herein, a preliminary sequence, dating from 2017-2018 is used to reconstruct instabilities that have been recorded on the walls of one of these distinct pillars. The analysis was first targeted at locating source areas of minor rockfall events. Three such features were identified on the pillar north face, by recognizing negative change in point cloud surface, i.e., deficient rock mass. Underneath them, in the base of the pillar, less distinctive mass accumulations are noticed in the post event point cloud, which likely represent the runout zones. All source features depict irregular andesitic fragments of about 1–2 dm³ in volume, positioned in the upper third of the pillar. Trajectories of these detachments were simulated using 2D and 3D geotechnical tools. Rock fragment and ground properties required for running the simulations were assumed from field observations and index properties determined using the portable tools (SH70 needle penetrometer, Schmidt’s hammer, etc.). Reconstructed trajectories show good correlation with the post-event (2018) point cloud, where accumulated material, i.e., suffice of rock mass coincides with runout locations. Due to relatively ductile ground, fragments did not bounce significantly, and their kinetic energy is quickly dissipated, making them to stop within a close range around the pillar perimeter. In perspective, further systematic monitoring could help determine the rockfall rate, and related loss of mass on an annual basis. Such findings could help understanding the erosion and weathering process better and undertake strategies towards the site’s sustainability and resilience to climate change and extreme weather conditions.

Rockfalls are threatening natural hazards because of their rapidity and the few precursory phenomena associated, that, in highly frequented areas, result in a high geological risk. Stability analyses for risk mitigation strategies depend on the knowledge of discontinuities constituting the rock mass. However, the manual characterisation of rock joints can be hindered in case of large and/or inaccessible areas. This is the case of the Vallepietra shrine (Central Italy), site of historical and religious importance (whose origin dates back to the 11th century), destination of thousands of pilgrims, and located beneath a 200-m-high and 700-m-wide sub-vertical calcareous rock wall. Within a preliminary site characterization, a comparison between manual and semi-automated procedures of rock mass discontinuities recognition was performed on a test area close to the shrine, where in addition to a geomechanical station, a laser scanner survey was performed to obtain a point cloud of the rock mass. The latter was analysed through Discontinuity Set Extractor (DSE) software to obtain the main discontinuity sets in terms of dip and dip direction and then compare them to the outcomes of the manual survey. The results obtained from the two techniques were in good accordance and led to the recognition of four main discontinuity sets. Rock blocks were also retrieved from the rock wall for laboratory tests. Cylindrical samples of rock material were trimmed out of the blocks to perform unconfined compression (UCS) and splitting tensile strength (STS) tests. The use of radial and axial strain gauges allowed to evaluate the elastic moduli of the rock material. The results in terms of strength and stiffness were in good agreement with literature on similar rocks in Central Italy. The joint friction angle was determined by performing tilt tests both on jointed blocks and on specimens with planar-sawed joints, obtaining values typical of moderately weathered rock. The orientation of slope and discontinuities, together with experimental laboratory and field data (UCS, STS and Schmidt Hammer) on rock material and joints were used to determine the rock and slope mass ratings (RMR and SMR) as well as to perform kinematic analyses to check planar/wedge sliding and toppling failure compatibility. As a future perspective, by extending laser scanner surveys to other sectors of the rock wall and by further refining the point cloud analysis, the geomechanical characterisation of the entire rock wall could be achieved overtaking the manifest limitations of manual surveying in such distinctive areas.

Natural stone has been used for façade applications for centuries. Initially, stone elements were rather thick, when used as construction elements, and the durability was appropriate. Scientific research on properties of marble began in the late 19th century. In the years following, the thickness of natural facade stones decreased from over 1000 mm (as in construction elements) to typically 20-50 mm (in cladding applications) because of new cutting technologies and equipment being developed by the industry. Even though most marble claddings perform satisfactory, durability problems have begun to appear at an increasing rate after some 50 years of using thin cladding Well-known buildings such as the Amoco Building in Chicago, SCOR tower in Paris, and the Finlandia Hall in Helsinki have had their marble cladding replaced after less than 30 years at the cost of many millions of Euros. The deterioration gives a very considerable change in the appearance of the panels. They bow, warp or break. Most cases of bowing involve Italian marble from the Carrara area, simply because it is the most widespread and used marble type. It is, however, vital to emphasize that many building facades with Carrara marble perform well, and furthermore other marbles and limestones from other areas also exhibits durability problems. This study is dedicated to the physical and mechanical characterization of two marbles and two limestones: Carrara (IT) and Ruivina (PT), Pedra de Ançã (PT) and Estremadura (PT). It combines the analysis of experimental results (physical, mechanical, and aging properties) to allow the study of potential mechanical strength decay over time. The selected natural stone materials are often used as cladding materials and are different in mineralogy, texture, preferential orientation of grain shape and grain size distribution. The reduction in mechanical resistance was evaluated by initial bending strength and after thermal shock and freeze-thaw aging tests under standard test conditions according to the current standard in force. Other properties such as compressive strength, anchorage breaking load, elastic modulus, ultrasound velocity, volume mass, water absorption at atmospheric pressure and by capillarity and other physical indices were accessed. Result show that marble and limestone decay is linked to temperature variations and moisture. These factors are seen key features in the degradation processes. An updated and comprehensive review of the selected stones structural decay was made to consolidate the understanding of façades structural degradation.

The freeze-thaw action is an important decay process that frequently affects building rocks in cold regions. This phenomenon can lead to a degradation of their physico-mechanical properties, affecting the service life and compromising the aesthetic and structural functionality of stone construction elements. The aim of this research is to establish the physical and mechanical damage induced by the recurrent frost action on a porous limestone from the province of Alicante (south-eastern Spain) marketed worldwide as building material. For this purpose, specimens of the limestone were firstly fully saturated in water, then subjected to 20 and 40 freeze-thaw cycles and finally oven-dried at 70 ⁰ C until constant mass was reached. Each cycle lasted 24 h, consisting of 8 h of freezing at -20 ⁰C and 16 h of thawing in water at 20 ⁰C. Once the abovementioned conditioning treatment was performed, physical and mechanical parameters of the limestone, such as absorption, effective porosity, P- and S-wave velocities and uniaxial compressive strength, were determined in laboratory and compared with the corresponding parameter values of the intact (untreated) rock. The results showed that the freeze-thaw action increases the absorption and effective porosity and reduces the density, P- and S-wave velocities and uniaxial compressive strength of the porous limestone. In addition, the most-used coefficients to describe its weathering against the cyclic freeze-thaw action were calculated, which served to clarify its potential utilisation in cold climatic zones.

The integration of Rock Engineering in European Geotechnical Standards is one of the great achievements of the future Eurocode 7: 202x (EC7). The design of a geotechnical structure, according to prEN1997:202x [1], comprises five major tasks:1. Reliability management: a series of classifications that combine to place the geotechnical structure into a single Geotechnical Category. 2. Ground investigation: whose main outputs are a representation of the ground and groundwater at the site, known as the “Ground Model”, and the results of field and laboratory tests relative to different ground properties and test parameters. 3. Design verification: covering all the procedures to verify that no limit states are exceeded in any design situations that the structure encounters during its service life. 4. Design implementation: in which the structure is constructed while meeting the design assumptions and other detailed plans developed during the design phase. 5. Reporting: all work carried out during the design and execution of the geotechnical structure must be documented by carrying out the following reports: Geotechnical Investigation Report (GIR), Geotechnical Design Report (GDR) and Geotechnical Construction Record (GCR). The paper shows the different tasks that the designers must perform to verify the stability of a rock excavation: reliability management, ground investigation and design verification. During this process, the various new concepts that appear in the future EC7 (Geotechnical Category, Ground Model, Representative values, Design Situations and Design Cases) were applied. The results obtained show that the problem of a rock slope stability can be successfully solved in the frame of the Partial Factor Method, developed in the future EC7. The case under study is a rock slope produced by an excavation of an open pit next to an existing building. The excavation depth is 15 m (5 m in soil material and 10 m in rock material) with an angle of slope of 90º, as can be seen in Figure 2-left. This case was proposed by Guido Nuijten as part of the works performed by the final project team of the future Eurocode (CEN TC250-SC7-PT6).

The conventional design approach of any type of passive protection work aiming at reducing the risk associated with rockfall is energy-based: the total kinetic energy of the falling block in a given position of its trajectory (action, in Limit State Design (LSD) terminology) must be compared to the maximum energy absorption capacity of the protection work (resistance, in LSD terminology). The LSD approach, implemented in Eurocode 7 (EC7), shows some limitations in the case of unconventional geotechnical problems such as rockfall phenomena, since the main parameters of these systems are not considered. To overcome these limitations, one proposed solution is the application of Reliability Based Design (RBD) approaches through the definition of a reliability index, a useful and complementary tool to provide geotechnical structures with a uniform probability of failure. The RBD approach deals with the relationship between the loads that a system must support and the system's ability to support those loads. The RBD therefore shifts the analysis towards a fully probabilistic one, in which each parameter is considered a variable expressed by a known Probability Density Function (PDF). In this work, particular attention has been given to innovative rockfall protection structures such as hybrid barriers and/or attenuators: they do not stop the block by capturing and retaining it in a deformable net, but by dissipating its kinetic energy (up to 0 for hybrid barrier) and forcing it along a trajectory close to the ground or guiding it towards a collecting area. Therefore, in ideal conditions, the block does not stop within the net itself. Considering the applicability of RDB approach, the paper focuses on the response of these structures to the impact of the block and their absorption capacity at different stress levels. The rockfall barriers are made up of a series of structural elements (cables, interception panels, pots, anchoring system, …) which contribute together with the absorption of the impact energy. In this context, numerical modelling represents a powerful solution to reproduce the behaviour of these structures subjected to dynamic impacts at different Kinetic Energy levels. With this purpose 3D numerical simulations by FEM software ABAQUS were carried out, starting with simplified models to identify which parameters most affect the system response. In addition, different structural element components were analysed to reproduce their behaviour both in static and dynamic conditions to test their absorption capacity useful for the RBD approach.

Rock engineering projects that implement the observational method often use a ‘traffic light’ scheme to indicate the system’s status. Such schemes are convenient in practice, but subjective and ambiguous definitions of performance associated with each colour in the scheme and lack of clarity of risks are drawbacks. We tackle these deficiencies by proposing a probabilistic traffic light system with an extended colour range. Simulations using the convergence-confinement model (CCM) for a circular tunnel are presented to demonstrate the system. The geometry and colours of the bivariate cumulative probability distribution provide essential information regarding the system’s behaviour. We conclude that a probabilistic traffic light system can help assess the performance of rock engineering projects being designed and constructed using the OM in accordance with Eurocode 7.

For improving the quality and reliability of geotechnical investigations process, the concept of 'influence region' has been recently proposed. The concept of influence region is an attempt to move from 'experience-based' geotechnical investigations to a 'mathematical equation-based estimation and understanding' of ground investigations. It’s an attempt to improve quality of existing geotechnical process and to make it more reliable. Although the newly proposed concept of influence region is based on author's field experience and conceptualized while working in real life projects, its theory still needs to be tested and validated. Considering need of testing and validation of this new concept of 'influence region', and proving it's theory, in this paper we are proposing different methodologies for field and laboratory tests. The paper will cover geotechnical investigations in different ground conditions i.e., soft-medium-hard conditions for both soil as well as for rock and will propose testing methodologies for both laboratory and field testing. The proposed methodologies will consider geo-mechanics, hydraulics, deformation parameters for soil and rock for testing the concept of influence region. To explain practical application of the concept we will be estimating influence region of RQD* (*Rock Quality Designation) parameter. RQD is most commonly used parameter for accessing the quality of rock. RQD is one such parameter which is applied in almost all empirical formula for accessing quality of rocks. The expected outcome of this paper is to have testing and validation methods for both lab as well as for field testing for proving the concept of 'influence region' of geotechnical investigation points, sampling zone. Also, to show the practical application of the concept, an example of RQD influence region estimation and its equation is presented. Author's view is as influence region concept is an equation-based understanding of geotechnical ground investigations, it has potential to be included in Eurocode/ ISO standards. By providing testing, validation methodologies and showing practical application of the influence region concept, this paper will serve as a scientific tool to geotechnical engineers.

Assessing the suitability of geological formations as safe locations for seasonal hydrogen storage requires in-depth geological knowledge and good engineering practice. Establishing the safety and viability conditions of such projects requires solid multidisciplinary experimental evidence. In this context, the role of seal formations is crucial, in particular when considering H₂-tightness and their related transport properties. While there is a wide number of works addressing the performance of low-permeability seal rocks (salt formations, shales, etc.) when exposed to a variety of gasses (CO₂, N₂, CH₄, etc.) there is a significant lack of information on the behavior and interaction of H₂ with natural rocks under realistic geological storage conditions. In this work we will present results of experimental works developed on seal rock materials of potential interest for H₂ storage (Late Miocene marls) under representative field conditions (60 ºC; 17.5 MPa vertical stress; 8 MPa pore pressure; dry density ~1.7 g/cm³). Due to the poor machinability of the rock, a sample reconstitution methodology was required to perform the tests. These included a stepwise sequence of liquid (in situ sampled formation fluid; 4.26 mS/cm) and gas (H₂; 99.9992 purity) steady-state injections aimed at assessing its intrinsic permeability and breakthrough pressure either in single and multiple drainage/re-imbibition stages.

The creep behavior of rocks significantly affects the long-term stability of underground spaces. This phenomenon becomes more remarkable in the case of soft rocks, deep underground construction, and rocks subjected to high stresses. A better understanding of the creep behavior of rocks is crucial for the analysis of the time-dependent behavior of rocks. In this study, a new creep constitutive model is proposed by replacing a Newtonian dashpot in the Burger model with the fractional derivative dashpot and introducing a viscoplastic element to model the accelerated phase of rock creep. The proposed model is validated by the creep test results of soft rocks, which shows that this model can comprehensively describe rock creep characteristics.

The ideal circumstance for accumulation and passage for CBM gas is well developed pores and cracks in gas reservoirs. To explore the multi-scale characteristics of pores, two coal samples have been collected from Raniganj Basin, which has been of interest to scientists and policy-makers due to its abundance of CBM resources and favorable conditions for CBM enrichment in eastern India. Quantitative pore features as evaluated by fluid based method (low-pressure N₂ and Co₂ adsorption) and image based method (Field Emission Scanning Electron Microscope) in this investigation. By utilizing these methods, Characteristics of nano pore including pore size distribution, pore volume, specific surface area and pore shape has been understood. To study the effect of pores on methane adsorption, a full scale pore estimation model has been introduced with the combination of BJH, BET, Langmuir and NLDFT model to establish the micropore (0.4-1.6 nm) and mesopore (1.6-20nm) attributes. According to the case study’s analysis, Raniganj coal samples have a certain specific surface area and mesopore and micropore volume, varying from 8.2913 to 11.8303m²/g and 0.0165 to 0.0188cm³/g for mesopores and 32.042 to 39.416m²/g and 0.014 to 0.017cm³/g for micropore. Mesopore size distributions are multimodal and micropore size distributions are unimodal. The surface fractal dimension of both coal samples is determined using the area-perimeter approach based on microphotographs. The value of the fractal dimension ranges from 1.17 to 1.30. These findings of the study demonstrate that the coal surface has a clear fractal aspect and that fractal theory is a useful tool for understanding the complicacy of pore morphology.

It is not uncommon that seismically active zones are generated away from the region where anthropogenic activities, such as mining excavation and fluid injection, caused a severe change in the in-situ stress. It is still quite challenging to predict the occurrence of such dynamic instability in the remote regions because the stress change in such regions is relatively small and the rock mass is presumed to be stable from a theoretical point of view. It can be deduced from previous field measurements that one of the factors contributing to the occurrence of the rock mass instability is pre-existing stress heterogeneity resulting from the macroscopic stiffness variation of the rock mass. The present study addresses this problem by performing the numerical simulation of the in-situ stress state in a sedimentary basin with a boundary traction method whilst considering the difference in stiffness among geological layers as well as the geometry of the boundary. First, a model parametric study is conducted whilst changing the stiffness of each geological layer. The result indicates that the difference in stiffness between the basement and sedimentary rock significantly disturbs the in-situ stress state, leading to a remarkable increase in deviatoric stress from the hydrostatic stresses applied to the model boundaries. The degree of the stress discrepancy is more pronounced with the decrease in the stiffness of the sedimentary rock situated above the basement. Then, the geometric effect of the geological boundary between the basement and the sedimentary basin is investigated. Interestingly, the result shows that the deviatoric stress of the rock mass increases above a convex geological boundary, indicating a large potential for instability. In contract, when the boundary is concave, the maximum stress decreases above the boundary, but the stress increases in the basement beneath the boundary. This implies that the risk for rock mass instability decreases above the boundary and vice versa. These results clearly shed light on the mechanism of the dynamic instability taking place away from the region where the in-situ stress was severely disturbed due to anthropogenic activities. Importantly, the presented method needs to be combined with the heterogeneity of rock mass strength in the future in order to develop a more reliable prediction method for the dynamic instability of rock mass.

Advanced geological prediction in tunnels primarily focuses on the weak layer, identified by shear wave velocity. Traditional methods using longitudinal and transverse wave velocities have low accuracy due to ambiguities. Surface waves offer a more precise alternative, though "mode kissing" during dispersion can cause misinterpretations, increasing construction risks. We propose a novel model-substitution method to invert weak layer models and spatial measurement data from tunnels, improving prediction accuracy. Our approach, validated by comparing with advanced drilling results, effectively inverts velocity structures of weak layers, offering a new method for geological prediction using surface-wave and reflection-wave techniques.

The old Grohovo rock avalanche, near the City of Rijeka, Croatia, was activated in 1870 and reactivated in 1885 after prolonged heavy rain period. In its reactivation this rock avalanche of about 16 Mm3 buried 7 houses in its foot. The dimensions of the landslide are length of 490 m, width of 810 m and the slip surface depth of about 85 m. The landslide is situated at the Rječina River Valley slope built in siliciclastic flysch deposits in the bottom and limestone rocks at the top of the valley slopes. The slip surface passes through limestone rock mass at the top of the slope and through flysch rock mass in the lower part of the slope. The Grohovo rock avalanche, the most probably dormant landslide in the last 140 years, was never deeply investigated. In this manuscript, preliminary results of landslide mechanism based on remote sensing surveys are presented. Based on analysis of these data, the landslide model is estab-lished and its activity in the last 70 years was estimated.

The understanding of preparatory processes like thermo-mechanical deformations in charge of natural and man-made rock slope stability strongly condition the efficiency of triggering actions. i.e., rain- and snowfalls, dynamic vibrations, blasts which can operate as near-surface processes. In this sense, the qualitative understanding of preparatory and triggering factors is often limited to qualitative register, and limited is the knowledge about the role (single or in combination) of the environmental conditions that contribute to the occurrence of rock failures (mostly falls and sliding) in critical and subcritical regimes. To achieve the general objective to predict timing and location of ultimate failures in rock walls and quantitatively assess cause-to-effect empirical relationships, an experimental site integrating geotechnical and geophysical monitoring is active since 2016 in Central Italy in an abandoned quarry, namely the Acuto Field Lab managed by the “Sapienza” University of Rome. The Acuto Field Lab acquisition focuses on i) full monitoring of weather conditions and rock strain acquisition by strain gauges and joint meters; ii) 3D InfraRed Thermographic monitoring and contact thermal monitoring, iii) seismic noise measurement devoted to assessing permanent changes in physical and mechanical parameters, iv) Acoustic Emission (AE) and Microseismic (MS) event detection as precursors of incipient failures. The data collected to date supported, in an analytical stage, the numerical quantification of inelastic deformation occurrence in rock mass under periodic forces through stress-strain modelling. The main outcomes focused on the effect of temperature changes over the rock surface and across joints, highlighting the response of major rock fractures and microcracks to the experienced temperature fluctuations at different depths (i.e., thermally active layers). Geophysical monitoring registered the dynamic response of the exposed rock wall under daily and ordinary thermal cycles and a non-ordinary weather event, highlighting, as preliminary results, the occurrence of acoustic emissions as effect of cooling relaxation. Under intense weather events that caused fast freezing, low-frequency MS signals have been attributed to different driving mechanisms caused either by thermal dilation or contraction and by freezing-thawing mechanisms.

Detecting displacement trends is critical in engineering geotechnics to prevent structure collapse, especially in mining operations where monitoring ground movement is vital. Tailings Storage Facilities (TSF) store mining by-products, posing risks of dam collapse. Limited global data makes TSF management complex, accentuating the need for rigorous monitoring. Rio Tinto, collaborating with Atalaya Mining and CSIC, aims for a digital transition to enhance geodetic and geotechnical monitoring. Utilizing Hexagon GeoMonitoring Hub (GMH) platform, data from various sensors are integrated for comprehensive analysis. This strategy allows to detect a slow movement estimated on average at 1 mm/month; the correlation between the data made it possible to understand where the movement is located (with a different displacement trend from the top to the bottom portion), the direction of movement and the structural discontinuities of the dam. This study presents insights for future modeling and best practices in mining and civil engineering monitoring, benefitting structures like road slopes and water dams.

In November 2022, near the village of Castrocucco di Maratea (PZ), a severe rockfall, over 5000 m3 of dolomitic rocks, affected the national road n. 18 ”Tirrena Inferiore” at Km 241+600, whom surveillance and manutention are operated by ANAS spa (Gruppo Fs Italiane), the Italian leading Concessionaire of national road and motorway network. In the 25 Km section between Sapri and Castrocucco di Maratea, the road is a very tortuous, panoramic and tourist itinerary with a two-lanes single carriageway. The road is “carved” in intensely fractured and karst rock cliffs subjected to fast landslides. The route is the only national road serving a critical seaside tourist area and provides a direct connection between the coastlines of Campania, Basilicata and Calabria regions. The rockfall of November 2022 started as a major planar sliding developed on a low-angle fault and triggered by the intense rains of the preceding month. It destroyed part of the road with complete collapse of the retaining structures, fortunately with no fatalities nor injuries. As a consequence, the road had to be closed, and an alternative viability was instituted. However, the road needed to be reopened before the start of the approaching summer season. ANAS SpA, in cooperation with other national and local authorities, accomplished to rebuild the road body and to mitigate the hazard. On the 14th of July the road was temporarily reopened up to the 30th of September 2023, with traffic restrictions. To enhance traffic safety and ensure the functionality of the protection structures, ANAS activated the onsite surveillance and implemented a remote real-time monitoring activity of the slope movement integrated with automatic real time early warning systems. The monitoring points were defined following a structural analysis of the fracture system. The latter was performed by means of field surveys and remote analysis via Virtual Outcrop Models (VOM) developed after image acquisition via drones. This system consists of automated topographic measurements integrated with a meteorological station and remote-controlled security cameras. Furthermore, inclinometers and strain gauges are installed on the rock slopes. A Virtual Machine Service (VMS) receives the monitored data via a wireless system. The software identifies settlements and/or displacements that exceed the threshold limits and sends an e-mail alert. This article presents the monitoring system made to prevent or reduce risks in case of rock mass deformation and consequent rockfalls, showing how early warning could play a significant role for a safe road management.

Reverse k-ratio and geological complexities have significantly contributed to design challenges and instability within the rockmass. The rock engineering design process within this shaft had to consider that mining had to occur in a rockmass that included large blocks of ground truncated by major geological weaknesses, reef planes with different strike, dip orientations, and a rockmass impaled with joint and fracture planes. The off-reef tunnels in the weaker shale rock type tend to squeeze and are supported with ring sets when the deformation occurs within these tunnels. Designing tunnels near this rock mass considered the presence of a weak, highly altered Westonaria Formation Lava, which directly over-lays the high-grade Ventersdorp Contact Reef conglomerate within the shaft. Westonaria Formation Lava has significantly contributed to instability, posing an immediate risk to shaft barrel stability and a medium- to long-term risk to continued ore extraction within the excavating environment.

The stability graph method is a widely used empirical method for dimensioning open rooms/stopes and support design based on stope geometry and stability number. Despite numerous developments, such as expanding databases and introducing new concepts and factors, a comprehensive understanding of its underlying mechanisms and universal applicability necessitates thorough numerical and theoretic analyses across various scenarios. This paper presents a rigorous investigation employing numerical models featuring multiple joint sets to replicate the structurally controlled failure of open stopes, a predominant failure type encountered in the stability graph databases. Detached blocks within these models are treated as overbreak and identified by defining thresholds for normal and shear displacements on joint planes. The concept of equivalent linear overbreak/slough (ELOS) is referred to in the numerical models to quantify the failure, similar to the ELOS stability graph method. The results obtained from numerical models and empirical method for the cases with different stope dips and sizes, and different critical joint set orientations have been compared to evaluate the performance of stability graph under different scenarios. It is found that the agreements between the numerical and empirical results on different surfaces of the open stopes are different. Notably, the adaptation of a modified stress factor A significantly enhances agreement, particularly for the hanging wall, characterized by a lower confinement stress state. Furthermore, larger ELOS values on the back surface of stopes with a critical joint set angle of 45 degrees are identified compared to those with a critical joint set angle of 30 degrees. It has opposite trend to the stability graph results. To address this inconsistency, modified factor B values are proposed for different surfaces based on normalized analyses of numerical models with varying critical joint set angles. In conclusion, the numerical simulation results align well with stability graph outcomes when using modified factors, A and B. This research has improved our understanding of the empirical stability graph method and promotes its reliability in predicting the stability state and unplanned dilution in open stopes. These insights are significant for mining engineers and practitioners seeking more accurate and robust stope stability assessments in their operations.

In opencast mines, overburden removal is the first step for mineral extraction, which is disposed of as dump slopes made of several benches. Shear strength is the most significant factor for establishing the slope stability of the dump. The laboratory techniques to determine the shear parameters, such as cohesion (C) and internal friction angle (Φ), don’t represent the actual behavior of the samples. In the present work, a large-scale in-situ direct shear apparatus is fabricated for determining the shear parameters of a dump in constant normal load (CNL) condition. The apparatus was tested over dumps of iron-ore mines in Odisha, India. The peak shear stresses corresponding to various vertical stresses, viz. 25, 50, 75, and 150 kPa, were found to determine a Mohr-Coulomb failure envelope. The in-situ C and Φ were measured to be 31.41 kPa and 48.99⁰, respectively. These in-situ tests give realistic data, which is very helpful for the optimistic design of overburden dumps.

The limit equilibrium model in boundary element codes has become a popular method to simulate the behaviour and failure of pillars in underground workings. Albeit good results have been obtained through this model, the calibration of this model is cumbersome due to the multitude of parameters that require calibration. An alternative solution was presented to verify and calibrate the model through the use of physical modelling in a laboratory. For the experiments, an artificial pillar material was used and cubes were poured using the standard 100x100mm civil engineering moulds. The friction angle between the artificial “pillar” and the platens of the testing machine was varied by using soap and sandpaper. Different modes of failure were observed depending on the friction angle. The results of the preliminary numerical modelling indicated that the model is able to simulate the stress-strain behaviour of the laboratory models, thereby verifying that the limit equilibrium model appears to be a useful approximation of the pillar failure. This paper further investigates the numerical modelling of the laboratory experiments conducted.

The complex geometric morphology of single rough-walled rock fractures, coupled with the occurrence of nonlinear flow, adds complexity to the fracture flow process. Despite decades of research on nonlinear flow behavior in single rock fractures, existing models still fall short of adequately capturing such behavior during shearing. In this study, a series of coupled shear-flow tests are conducted on single rock fractures under constant normal loads. The results show that the Forchheimer equation effectively describes nonlinear flow, with its nonlinear coefficients associated with fracture geometries. The evolution of fracture geometries induced by shearing is quantified and its impact on nonlinear flow is considered. An empirical equation is then proposed, incorporating the peak asperity height and hydraulic aperture, to evaluate the Forchheimer nonlinear coefficient. The proposed equation is validated through experimental results, demonstrating its effectiveness in characterizing nonlinear flow behavior in rock fractures during shearing.

Rock mass is the host media in a wide range of geotechnical applications. The failure behaviour of rock mass is complex and strongly influenced by various geological structures, from micro to macro scale. To have a proper structural design and safe construction, a thorough understanding of failure mechanism around an underground excavation is essential. That includes an investigation of the cracking processes of rock mass and, in particular, how micro-cracking around the excavation progresses to macro-cracking of rock mass. In order to reveal the rock mass cracking process of an underground excavation, laboratory investigations on real rocks containing an opening, can provide a proper understanding of its complex behavior. In this regard, different advanced techniques can be implemented to monitor the cracking process around the excavation in real time and to explore the rock mass behavior more deeply. This paper aims to experimentally investigate the fracture evolution and damage behavior of rock specimens containing an opening under the uniaxial compression, incorporating digital image correlation (DIC) method and acoustic emission (AE) technique. For this purpose, uniaxial compression tests were conducted on granitic rock blocks containing a circular opening. In addition, four strain gauges were installed in as many directions around the opening to record the local strains. The synchronized AE output parameters and DIC plots with the stress and displacement data extracted from the servo-controlled loading frame, together with strain gauge data have been compared and analyzed in detail to reveal the mechanisms of crack coalescence. Finally, different criteria have been implemented to estimate damage stress threshold values. Combined analysis of AE parameters, DIC and stress-strain data allows to identify and discriminate different cracking stages including crack initiation, growth, coalescence and damage in tested specimens and their results are mutually consistent. AE results provide with reliable information to characterize the fracture evolution stages and different stress thresholds. Likewise, the local strain levels recorded by strain gauges are in a fair good agreement with the strain field measured with DIC. The type of crack initiation and failure around circular opening are also well characterized and in accordance to the theoretical crack distribution around excavations. The results of this study provide significant insights of the cracking processes in rock mass around an opening.

Flysch materials are a common source of slope instabilities and other geotechnical problems. Some attempts of characterizing such materials have been done, probing to be a challenging aspect. One European region where flysch materials are abundant is the Spanish Basque Arc Alpine region. A broad geological-geotechnical investigation was conducted on 33 locations spread in an area of approximately 100 km² in the Spanish Basque Arc Alpine region to geomechanically characterized the “Upper Cretaceous Flysch” materials found in the area. Such characterization was done following a GSI vs. uniaxial compressive strength of the intact rock chart given by other authors. Even though that procedure showed to be appropriate, values of Hoek-Brown parameters proposed based on such chart, showed not to match very well with the ones obtained in the laboratory for the 33 points analyzed. This caused the estimation of shear strength parameters of flysch materials to be poor. To improve it, Artificial Neural Networks were used. These artificial intelligence algorithms are of common use in engineering and enable to find no-linear correlations which may be difficult to find otherwise. Results show a very good performance when using Artificial Neural Networks, achieving determination coefficients R² between laboratory values and numerical ones close to 1.

The continuous convergence monitoring during and after excavation is an important tool in the application of the observational method for tunnels design (Schubert 2008. Geomech. Tunn. 1(5):352–357). Previous works have shown that, the direct analysis of convergence measurements with empirical models allows reliable long-term predictions of ground deformations. It is shown that, by monitoring convergence for a few tens of days, these models can provide valuable insights for the design of support systems and the evaluation of their performance in time (e.g. Sulem et al. 1987. Int J Rock Mech Min Sci Geomech Abstr, 24(3):145–154; Guayacán-Carrillo et al. 2016. Rock Mech. Rock Eng. 49(1):97-114; Liu, et al. WTC 2019). During the last decade, machine learning techniques have experienced vast growth in geotechnical engineering. These techniques present advantages concerning their computational performance and their applicability to high-dimensional non-linear problems. With the emerging use of these techniques, some questions arise as: (1) how these ones will contribute to the design of underground structures? and (2) what is its efficiency and accuracy using small datasets, as it is the case in rock engineering projects? The present work aims to propose a simplified Symbolic Regression (SR) approach in order to evaluate its applicability on the convergence evolution prediction. SR is a machine learning technique that aims to identify an underlying mathematical expression that best describes a relationship between input and output parameters (Stephens 2019. gplearn.readthedocs.io; Koza, J. (1992). MIT Press). In this work, special attention is given to anisotropic closure evolution, which depends on the anisotropy of the initial stress state and the intrinsic anisotropy of the rock mass formation. Moreover, the time needed on convergence monitoring is also studied, by taking into account different time intervals (corresponding to the duration of convergence monitoring). The results show that SR present a good predictive accuracy in comparison with the semi-empirical law proposed by Sulem et al. (1987) [Int J Rock Mech Min Sci Geomech Abstr 24(3): 145–154]. It is observed that this approach performs well with the small dataset used in this study and can be considered a useful alternative.

The rock mass properties are crucial for any structural design and the estimation of these properties is done using the Geological Strength Index (GSI). This study introduces a methodology to predict the GSI values using advanced image processing and Artificial Neural Network (ANN) techniques. The pictures and the face mapping data from an Iron ore mine are taken and using image processing techniques, including black-and-white conversion, joint highlighting, and noise reduction, the fractal dimensions of the rock faces are evaluated. An ANN model is developed which utilizes the fractal dimensions and the surface condition index as inputs and predicts the GSI values. This methodology aims to overcome the subjectivity of qualitative assessments, providing a more accurate representation of rock mass strength. The R2 value of the developed ANN model is 0.67 which indicates a positive correlation between predicted and qualitative GSI values from the standard chart.

The expansion of the underground infrastructure and the necessity to maintain the functionality of existing tunnels highlights the role of structural health monitoring to track the behavior of the structure. In the study performed, the focus is on segmental tunnel linings for deep and long tunnels. The aim is to reconstruct in real-time the stress field in the tunnel structure starting from a few monitoring data. The framework is based on the combination of finite element (FE) models of the lining in the hosting rock mass and machine learning algorithms, which are deployed for real-time estimation of the stress distribution in the lining. An approach based on synthetic data generated with FE simulations permits to reconstruct a thorough picture of the structural stress state based on a few monitored points. The method is applied to a full-scale test, in which three piled lining rings were tested under geostatic-like loads.

In NATM tunnel excavation sites, rock mass evaluation at tunnel face heavily influences the determination of support patterns of tunnel construction. Currently, this evaluation is performed by skilled engineers who score the rock mass according to several predetermined evaluation criteria. This method heavily relies on the subjective standards of the engineers. Thus, a uniformed and standardized evaluation method has not been established. In this study, the applicability of machine learning to rock mass evaluation is verified to achieve a qualitative evaluation method. A support vector machine (SVM) model was developed to predict the support pattern of one tunnel face to test applicability at tunnel construction sites.

We propose a new approach leveraging 3D Hough transform to detect discontinuity planes from traces in digital rock models, where clear planar surfaces are not apparent. Our method assumes that that the discontinuity plane behind a trace on the rock surface aligns roughly parallel to the trace's local direction, like a door rotating around a hinge. We begin by estimating local trace directions using multi-scale principal component analysis. These directions then inform the weighted voting of trace points within the Hough space. Peak-searching identifies initial planes, which undergo refinement to eliminate spurious or duplicate results. Applied to synthetic data and two natural outcrops, our method performed discontinuity extraction from traces with varying degree of success. This approach shows promise as an analytical tool in geology with potential for further optimization.

A significant rise in the world’s mean temperature (1.1ºC in 100 years) is produced mainly due to the emission of greenhouse effect gases (GHG), particularly carbon dioxide (CO₂) emission (IPCC, 2022). Carbon capture, storage, and utilization (CCSU) is being developed as an alternative to curbing the direct emission of CO₂ into the atmosphere. This process involves capturing CO₂ directly from emitting industries and injecting it underground in supercritical state (31.48ºC and 7.38 MPa). The primary goal is to identify a suitable geological reservoir capable of storing CO₂ for extended periods without the risks of migration. Among the various reservoir alternatives, a depleted oil and gas reservoirs stand out as a viable option. These rocks formations own high porosities, offering great void space for CO₂ storage, and their high permeability facilitates the injection of CO₂.

This paper explores the potential of using glauconitic sandstone extracted from a depleted oil and gas reservoir as a viable CO₂ storage option. The experimental investigation focused on observing the effects of subjecting samples to supercritical CO₂ (scCO₂) at 10.5 MPa and 60ºC for a duration of 30 days within the pressure cell at the UNPSJB's geomechanics laboratory (Argentina). Subsequently, a detailed analysis was conducted to evaluate the changes in petrophysical properties and mechanical behavior of the samples before and after the CO₂ ageing process. To achieve this, various mechanical tests, including direct tensile, uniaxial compressive, and triaxial compressive tests, were carried out at the geotechnical laboratory of CEDEX (Spain).

Based on the mechanical results obtained, it became evident that the mechanical strength of the sandstone decreased after undergoing the carbonation process, as assessed using the Hoek-Brown failure criterion. Regarding porosity, two primary modifications were observed. Firstly, there was a slight reduction in the sandstone's porosity after its exposure to carbon dioxide. Secondly, the pore size distribution exhibited variations, with an increased percentage of pores having smaller diameters. These findings suggest a preliminary hypothesis that chemical precipitation may have taken place within the larger diameter pores during the scCO₂-aging of the samples. To validate this hypothesis, additional analysis of the SEM, XRD, and XRF results will be conducted.

The study of salt structures has important guiding significance for oil and gas exploration and production in salt-bearing sedimentary basins. Previous studies have mainly focused on exploring the influencing factors such as syntectonic sedimentation, preexisting faults and preexisting salt diapirs of salt tectonic deformation. However, there is still a lack of systematic research on the effect of geometric properties of preexisting salt diapirs on the later stage shortening deformation. In this paper, particle flow method is used to investigate the geometric properties of preexisting salt diapirs such as its geometry, depth, width and the combination styles of preexisting salt diapirs on the geomechanics of salt-related structures during shortening. Model results show that the preexisting salt diapirs play an important role in geomechanics of salt-related structures. During shortening, salt bearing structures are prone to plastic flow, local accumulation and thickening, which affect the structural style of the overlying layers. The structural styles mainly include reverse faults and fault-related folds, box-folds, salt nappe structures and salt welding structures. The depth of preexisting salt diapirs is important for controlling the growth of diapirs. The width affects significantly the amount of shortening, which can be accommodated by extruded diapirs. The combination style of preexisting salt diapirs has a certain impact on the deformation of overlying salt tectonics. In addition, the reliability of the simulation is further verified by comparing the model results with the typical seismic profiles of salt tectonics in the Tarim Basin in China.

The storage of CO₂ in reservoir rocks is a crucial method for mitigating greenhouse gas emissions, but its application in Argentina, especially in the San Jorge Gulf basin, remains unexplored. Our study focuses on understanding how CO₂ affects the mechanical, petro-physical, and chemical properties of the Castillo and Pozo D-129 formations, which con-tain varying amounts of pyroclastic material. Rock samples were collected, core-drilled, and subjected to supercritical CO₂ conditions. Tests included uniaxial compression, air permeability, mercury porosimeter, XRF and XRD. Findings revealed that rocks after supercritical CO₂ aged treatment reduce the mechanical strength between 14 to 28%. Chemical analyses find variations in the mineral composition between carbonated and non-carbonated samples. Additionally, a reduction in porosity was observed in the treated specimens.

Robust geomechanical models are critical for forecasting and monitoring geomechanical issues associated with hydrocarbon production. Geomechanical responses to carbon utilisation and storage(CUS) have received little attention in the literature. This research proposes to investigate the poromechanical response of faulted depleted gas fields to CUS. The study area is located in the Bredasdorp Basin in South Africa. A one-way coupled geomechanical model is developed to gain insights into the geomechanical challenges related to CUS in faulted depleted gas fields. This model combines a dynamic model derived from earlier studies on the EM gas field with a 3D geomechanical model created using Petrel software. Particular attention is given to modelling the 3D petrophysical Young modulus in the underburden to obtain a more accurate mechanical response. Three geomechanical deformation case scenarios were formulated to assess the behaviour of the E-M gas field. The first scenario, known as the Depletion case, involved simulating natural gas production for nine years. In the second scenario, EGR_CO₂, EGR was simulated in the depleted gas field for 17 years, followed by CO₂ storage for 40 years. The final scenario, STORE_CO2, focused on injecting CO₂ into the depleted gas field over 40 years. The research outcomes unveiled notable observations regarding the geomechanical aspects. One signification revelation was the substantial contrast in the change in stress between the central and peripheral regions of the reservoir. Moreover, during the depletion phase, the reservoir experienced a subsidence of 30 cm, while an uplift of 18 cm was observed during the injection phase. Additionally, it was found that the uplift of the underburden compensated for the loss of fluid support, enabling the reservoir to uphold the overlying overburden despite the liquid phase depletion. However, after 40 years of CO₂ injection, the caprock exhibited failure, whereas the reservoir rocks remained stable. Furthermore, depletion heightened the probability of fault slippage, whereas CO₂ injection significantly reduced deviatoric and shear stresses, indirectly minimising the tendency of fault activation. Finally, the geomechanical issues associated with fluid injection in the reservoir during EGR depend on whether the production of natural gas balanced CO₂ injection. The reservoir is expected to remain stable if injection and production are balanced.

Naturally fractured/cleated coals are likely to develop viscoelastic strain rate-dependency during geological engineering activities such as coal mining, coal seam gas production and gas injection into coal seams. A full investigation of strain rate-dependency of naturally fractured coals is thus crucial to have safe and optimised coal seam operations. The micro-scale mechanisms causing the core-scale rate dependent observations, however, are not yet fully understood. In this study, we conduct a series of systematic multi-scale experiments to shed light on the mechanisms controlling the strain rate dependency of coal. The multi-scale experiments consist of core-scale triaxial testing of coal specimens with different strain rates under isotropic and deviatoric loading on different coal specimens. Every loading is followed with an unloading to analyse the energy dissipation during the tests and ensure that any bulk damage is avoided. A series of micro-scale tests on jointed coal specimen coupled with microscopy and digital image correlation (DIC) analysis is additionally conducted to further study the micro-scale processes controlling the macro-scale strain rate-dependent behaviour of the specimens. The results of triaxial tests on dry specimens show a clear strain rate-dependency under isotropic loading where a higher strain rate causes a stiffening effect on coal specimens. No strain rate-dependency is, however, observed for specimens under isotropic loading when fractures are closed by carbon dioxide (CO₂) saturation at different pressures nor under deviatoric loading for any specimens. Unloading of specimens, on the other hand, shows a considerable strain rate dependent energy dissipation in isotropic loading tests. The results of the micro-scale tests on coal’s fracture interestingly indicates that the asperities damage under normal stress controls the energy dissipation and strain rate-dependency of the bulk of specimens. The combined results reveal that, for the first time, the strain rate-dependency in naturally fractured coal within its elastic limit is attributed to damage of the asperities of pre-existing fractures under fracture closure process.

The key role of the shear strength of discontinuities and rock joints in the behavior of rock masses and in the safety of rock engineering projects where stresses are low when compared with the rock intact, such as dam foundations, slopes and surface excavations, or underground tunnels and caverns, is for long acknowledged. Several failure criteria – namely, Coulomb, Patton, Barton and Grasselli – can be used to derive design parameters from results of field investigations, mainly laboratory tests. The keynote will address some particular issues related to the shear behaviour of rock joints that can be found along the path between field investigations and design parameters: in situ versus lab tests and scale effects, joint surface roughness and its influence on the stress distribution along the joints, roughness wear and repeated shear tests on the same joint sample.