APPLICATION OF LASER SCANNING SURVEYING TO ROCK SLOPES RISK ASSESSMENT ANALYSIS

The methods for understanding rock instability mechanisms and for evaluating potential destructive scenarios are of great importance in risk assessment analysis dedicated to the establishment of appropriate prevention and mitigation actions. When the portion of the unstable rock mass is very large, effective actions to counteract the risks are complex and expensive. In these conditions, an optimal risk management cannot ignore procedures able to faster and accurately acquire i) geometrical data for modeling the geometry of the rock walls and implementing reliable forecasting models and ii) monitoring data able to describe the magnitude and the direction of deformation processes. These data contributes to the prediction of the behavior of a landslide if the measurements are acquired frequently and reliable numerical models can be implemented. Innovative geomatic techniques, based on GPS, Terrestrial Laser Scanning Surveying (TLS), automated total station and satellite and ground SAR Interferometry, have been recently applied to define the geometry and monitoring the displacements of unstable slopes. Among these, TLS is mainly adopted to generate detailed 3D models useful to reconstruct rock wall geometry by contributing to the estimation of geo-mechanical parameters, that is orientation, persistence and apparent spacing of rock discontinuities. Two examples of applications of TLS technique to the analysis of a large front in a quarry and of a rock shoulder of a dam are presented

Volume II: Mining Innovation

Contemporary exploitation of natural raw materials by borehole, opencast, underground, seabed, and anthropogenic deposits is closely related to, among others, geomechanics, automation, computer science, and numerical methods. More and more often, individual fields of science coexist and complement each other, contributing to lowering exploitation costs, increasing production, and reduction of the time needed to prepare and exploit the deposit. The continuous development of national economies is related to the increasing demand for energy, metal, rock, and chemical resources. Very often, exploitation is carried out in complex geological and mining conditions, which are accompanied by natural hazards such as rock bursts, methane, coal dust explosion, spontaneous combustion, water, gas, and temperature. In order to conduct a safe and economically justified operation, modern construction materials are being used more and more often in mining to support excavations, both under static and dynamic loads. The individual production stages are supported by specialized computer programs for cutting the deposit as well as for modeling the behavior of the rock mass after excavation in it. Currently, the automation and monitoring of the mining works play a very important role, which will significantly contribute to the improvement of safety conditions. In this Special Issue of Energies, we focus on innovative laboratory, numerical, and industrial research that has a positive impact on the development of safety and exploitation in mining

Thermal effects on geologic carbon storage

The final publication is available at Springer via http://dx.doi.org/10.1016/j.earscirev.2016.12.011One of the most promising ways to significantly reduce greenhouse gases emissions, while carbon-free energy sources are developed, is Carbon Capture and Storage (CCS). Non-isothermal effects play a major role in all stages of CCS. In this paper, we review the literature on thermal effects related to CCS, which is receiving an increasing interest as a result of the awareness that the comprehension of non-isothermal processes is crucial for a successful deployment of CCS projects. We start by reviewing CO2 transport, which connects the regions where CO2 is captured with suitable geostorage sites. The optimal conditions for CO2 transport, both onshore (through pipelines) and offshore (through pipelines or ships), are such that CO2 stays in liquid state. To minimize costs, CO2 should ideally be injected at the wellhead in similar pressure and temperature conditions as it is delivered by transport. To optimize the injection conditions, coupled wellbore and reservoir simulators that solve the strongly non-linear problem of CO2 pressure, temperature and density within the wellbore and non-isothermal two-phase flow within the storage formation have been developed. CO2 in its way down the injection well heats up due to compression and friction at a lower rate than the geothermal gradient, and thus, reaches the storage formation at a lower temperature than that of the rock. Inside the storage formation, CO2 injection induces temperature changes due to the advection of the cool injected CO2, the Joule-Thomson cooling effect, endothermic water vaporization and exothermic CO2 dissolution. These thermal effects lead to thermo-hydro-mechanical-chemical coupled processes with non-trivial interpretations. These coupled processes also play a relevant role in “Utilization” options that may provide an added value to the injected CO2, such as Enhanced Oil Recovery (EOR), Enhanced Coal Bed Methane (ECBM) and geothermal energy extraction combined with CO2 storage. If the injected CO2 leaks through faults, the caprock or wellbores, strong cooling will occur due to the expansion of CO2 as pressure decreases with depth. Finally, we conclude by identifying research gaps and challenges of thermal effects related to CCS.Peer ReviewedPostprint (author's final draft

A study on deformation of tunnels excavated in fractured rocks

La déformation due au fluage d'un massif rocheux autour d'un tunnel a été rencontrée fréquemment. Ce phénomène est évident où il y a des tunnels creusés dans la roche tendre, des masses rocheuses faible et fortement cisaillées, ou des massifs rocheux soumis à des contraintes in-situ élevées. La déformation due au fluage se produit fréquemment au moment d’excavation des tunnels longs où il y a des failles et des zones fracturées et cisaillées. Ce phénomène peut causer différents dommages sur des systèmes de soutènement en raison de la déformation excessive et des effondrements. La déformation excessive impose une ré-excavation de la section du tunnel, qui monte le coût supplémentaire, la durée de la réalisation du projet et le risque de la sécurité sur le projet. En plus, comme la stabilité de terrain est dans un état critique durant la ré-excavation, une petite négligence peut conduire à une grande caverne. Bien que la déformation de fluage est commune dans un massif rocheux à une faible résistance dans un tunnel très profond, mais ce phénomène a été observé dans des tunnels peu profonds. Une bonne compréhension des déformations causées par une excavation souterraine requiert la connaissance de l'interaction roche-support et l'interprétation des données de terrain. Auparavant, l’objet principal de la surveillance effectuée durant la construction du tunnel était des mesures de la pression au terrain imposé sur le revêtement du tunnel. Mais aujourd’hui, les méthodes modernes de construction de tunnel se concentrent sur la surveillance des déplacements pendant et après la construction. Afin de déterminer des déformations dans les tunnels, Panet et Sulem ont supposé que "Le tunnel a une section transversale circulaire et le milieu est homogène et isotrope, aussi le tunnel est suffisamment profond pour considérer que la distribution des contraintes est homogène". Mais dans le cas quasi réel, la distribution de la contrainte autour du tunnel est hétérogène et anisotrope. Dans cette étude, pour la modification des équations Panet et Sulem, certaines équations sont proposées en cas de matériau hétérogène et anisotrope pour généraliser le problème. La galerie de force motrice Seymareh a été considérée comme l’étude de cas. Celle-ci est une partie du conduit d’eau dans le projet de centrale électrique du barrage Seymareh. Ce projet est situé à l'ouest de l'Iran. Les données de surveillance de la galerie de force motrice sont collectées au moment de l’excavation du tunnel, et sont comparées avec les résultats de la modélisation numérique et de la solution analytique. Cette comparaison montre que les résultats des données expérimentales obtenues par la surveillance sont très proches des résultats de la solution analytique, mais il y a une différence entre les deux et la modélisation numérique. Il était prévisible, car l’effet d’autres activités comme l’excavation des tunnels verticaux n’est pas prise en compte dans l’analyse numérique et aussi dans la solution analytique. Il est évident que les autres activités comme l’excavation des tunnels verticaux et l'excavation du tunnel principal vers deux directions opposées, peuvent affecter sur les résultats de la surveillance. D'autre part, les données initiales utilisées dans l'analyse numérique et la solution analytique ne sont pas tout à fait exactes, car elles sont obtenues en tant que représentatives du massif rocheux de la région, mais pas pour une section particulière. Toutefois, le but de cette étude est le développement d'une solution analytique de la déformation dans les tunnels sur les conditions générales et la poursuite de cette étude pourra être plus développée.The creep deformation of a rock mass around a tunnel has been encountered frequently. It is particularly common in tunnels excavated in soft rock, heavily sheared weak rock masses or rock masses subjected to high in-situ stresses. Creep deformation in fault and shear fractured zones are one of the frequently encountered difficulties in long tunnel construction, which tend to cause failure of supporting systems due to excessive deformation and cavern. Excessive deformation would necessitate re-mining of the tunnel cross section, thus imposing impacts such as extra cost, extended time schedule and safety risk on the project. Furthermore, as the ground stability is in critical condition during re-mining, the slightest negligence would lead to major cavern. Although creep deformation is common to extremely poor rock mass under high overburden in a tunnel alignment, but however this phenomenon is not limited to tunnels with high overburden. A good understanding of the deformations caused by an underground excavation requires simultaneously knowledge of the rock-support interaction and interpretation of field data. Formerly, the main purpose of the monitoring carried out during tunnel construction was to measure the ground pressures acting on the tunnel lining. Modern tunneling practice emphasizes the monitoring of the displacements occurring during and after the construction. Panet and Sulem for determining of deformations in tunnels have assumed that "The tunnel has a circular cross section and around the tunnel, the rock is homogeneous and isotropic and also the tunnel is deep enough to consider that the stress distribution is homogenous". But in almost real cases, the stresses distribution around the tunnel is not homogeneous and isotropic. In this study, for modification of the Panet and Sulem equations, some equations are proposed in case of nonhomogeneous and anisotropic for generalizing of the problem. Seymareh power tunnel which is considered as a case study is a part of the powerhouse waterways system of the Seymareh dam and hydroelectric power plant project. The project is located in west of Iran. The monitoring data of power tunnel which are collected during excavation of tunnel is compared with the results of numerical modelling and analytical solution results as well as. The results obtained from comparison show although the field data, which are collected through the monitoring, are very close to the analytical solution results (approximately), but there is a significant difference between both of them and numerical modelling results. It was predictable; because the influence of the other activities such as excavation of shaft and surge tank in the numerical analysis and also analytical solution are not considered. It is obvious that other activities such as excavation of shaft and surge tank and also excavation of mean tunnel from other direction which were under operation at the same time can effect on the results of monitoring. On the other hand, the initial data which are used in numerical analysis and analytical solution are not quite accurate; because they are extracted as a representative of the rock mass of region, not for a particular section. However the goal of this study is development of analytical solution of deformation in tunnels on general conditions and pursuit of the study could be leaded to more development in this field

Mechanisms of failure of jointed rock masses and the behaviour of steep slopes

The geomorphological behaviour of steep jointed rock slopes has been studied using distinct element method computer models. In order to model steep slopes effectively, methodologies need to be combined from the studies of environmental modellers, geomorphologists and engineers. The distinct element method is ideal for the study of the development of jointed rock masses as the discontinuum approach can model the progressive failure of rock blocks along discontinuities. Initial, theoretical modelling identified the limiting boundary conditions between the multiple block failure mechanisms of toppling, sliding and toppling-and-sliding, based upon the discontinuity geometry for a theoretically modelled limestone rock mass. It is demonstrated that joint dip, friction angle and spacing exert the greatest control upon rock mass failure mechanisms. Two field locations, the Colorado Plateau and the Isle of Purbeck, have been chosen to provide a link between theoretical modelling and classic rock mass landforms which are controlled by variation in discontinuity geometry. In the Portland Limestone of the Isle of Purbeck, it is the joint geometry variation which influences development. Bedding steepens and average block size decreases in the coastal rock cliffs from east to west. Comparison between the model outputs highlighted that there is an increase in the rate of simulated cliff retreat from Winspit in the east to Durdle Door in the west. The Colorado Plateau rock cliffs form large, embayed plan-form escarpments and detached monoliths. It is the variation of joint set spacing in the cap-rock of cuesta-form composite scarps that controls development. Model results suggest there is a continuum of rock mass landforms, with buttes becoming detached at plan-form necks in the escarpment as determined by the joint geometry. The results show excellent similarity with the landforms observed in the field. This thesis introduces a research tool that can provide an understanding of slope behaviour

Rock Mass Evaluation of the Sardar Sarovar (Narmada) Dam and Underground Powerhouse, India

Geotechnical evaluation of the 163 m high concrete gravity Sardar Sarovar (Narmada) dam, under construction, and 1200 MW underground powerhouse (210m x 23m x 57.5m) and its ancillary structures has been done. The dam and powerhouse sites are occupied by basalt flows underlain by infra-trappean sedimentary rocks (Bagh beds) intruded by basic dykes. The area is structurally complex and seismically active. Intra-formational shears and sub-horizontal to low dipping weak layers like red bole, tuff, argillaceous sandstone having low values of shear parameters posed the problem of sliding stability of dam blocks. Concrete shear keys were provided as one of the remedial measures. Differential settlement was apprehended in the foundation of dam having varying physicoengineering properties and rock mass characteristics. Reinforced concrete mats were provided to treat the weathered and sheared rock mass and 34.5m deep reinforced concrete plug to prevent differential settlement of dam blocks located on river channel (dam base) fault. The horizontal seismic coefficient adopted for the dam is 0.125g. The construction of 1200 MW underground powerhouse located in basalt is nearing completion. During progressive excavation of the machine hall (cavern) cracks were observed in the 57.5m high shotcreted walls. Additional longer rock bolts/ cables/ tendons were provided as remedial measures. Draft tube and exit tunnels are passing through dolerite rocks dissected by chlorite-coated joints and slaked rock zones. Rib supports were introduced after observing behaviour of the rock mass and collapses in part of these tunnels

The Mechanical Behavior of Salt X

Rock salt formations have long been recognized as a valuable resource - not only for salt mining but for construction of oil and gas storage caverns and for isolation of radioactive and other hazardous wastes. Current interest is fast expanding towards construction and re-use of solution-mined caverns for storage of renewable energy in the form of hydrogen, compressed air and other gases. Evaluating the long term performance and safety of such systems demands an understanding of the coupled mechanical behavior and transport properties of salt. This volume presents a collection of 60 research papers defining the state-of-the-art in the field. Topics range from fundamental work on deformation mechanisms and damage of rock salt to compaction of engineered salt backfill. The latest constitutive models are applied in computational studies addressing the evolution and integrity of storage caverns, repositories, salt mines and entire salt formations, while field studies document ground truth at multiple scales. The volume is structured into seven themes: Microphysical processes and creep models Laboratory testing Geological isolation systems and geotechnical barriers Analytical and numerical modelling Monitoring and site-specific studies Cavern and borehole abandonment and integrity Energy storage in salt caverns The Mechanical Behavior of Salt X will appeal to graduate students, academics, engineers and professionals working in the fields of salt mechanics, salt mining and geological storage of energy and wastes, but also to researchers in rock physics in general

Numerical methodology to characterise heterogeneous rock masses

Tese de Doutoramento em Engenharia CivilThe uncertainties related with spatial variability and heterogeneities, naturally present in rock masses, play an important role in geotechnical engineering practice. A more accurate assessment and characterisation is increasingly in need due to their impact on the mechanical behaviour of heterogeneous rock masses. The aim of this work was to contribute with innovative methodologies to be used in the geomechanical characterisation of this type of rocks, as well as to reduce the uncertainty associated with the definition of prospection plans. The main methodology hereby proposed combines geostatistical techniques, which have proved to be efficient in identifying rock mass heterogeneities and in considering the spatial variability, with clustering techniques, so that a more realistic geomechanical model of the rock mass is obtained. Since the geotechnical information used to perform the numerical analysis of underground works has different stages, the proposed methodology was developed to take that feature into account. As a first step, the geotechnical parameters are simulated using geostatistical techniques, followed by their conversion into geomechanical parameters in a second step. A third step concerns the selection of representative realisations, with a minimum of three, to be used in the numerical analysis. Finally, the rock mass characterisation models are imported to a finite differences software to perform a mechanical behaviour analysis of the geotechnical structure. The numerical results are compared with the ones obtained from a deterministic approach that assumes the rock mass as a homogeneous medium. For the methodology validation, real data from two case studies were used: a Chilean gold deposit and the Salamonde II hydroelectric complex recently built in the North of Portugal. Concerning the methodology for optimizing prospection plans, the same geostatistical techniques were used to simulate the rock mass and to define the uncertainty metrics to use in the optimisation process, which relied on the Simulated Annealing algorithm. The randomness that exists in the definition of boreholes location was the stepping stone of this innovative methodology that intends to be a helping tool for professionals. As an output, one obtains the optimal spatial location for new boreholes, as well as their lengths, in order to decrease the uncertainty of the numerical model and to increase the geomechanical detail. It is worthy of notice that the two above mentioned case studies were also used in this methodology validation.A incerteza associada à variabilidade espacial e às heterogeneidades, naturalmente presentes aquando a caracterização geomecânica dos maciços rochosos, assumem um papel cada vez mais relevante na prática da engenharia geotécnica. Como tal, existe uma necessidade cada vez maior em obter caracterizações deste tipo de rochas heterogéneas de forma mais precisa e real. Assim, o principal objetivo deste trabalho foi contribuir com o desenvolvimento de metodologias inovadoras para serem usadas, tanto na caracterização geomecânica deste tipo de rochas, como na redução da incerteza associada à elaboração dos planos de prospeção geotécnica. Assumindo que as técnicas geoestatísticas são eficientes na identificação das heterogeneidades e na consideração da variabilidade espacial dos maciços rochosos, a principal metodologia deste trabalho combina estas técnicas com técnicas de clustering, utilizadas para a seleção de modelos geomecânicos mais realistas. Assim, numa primeira fase, é simulada a informação geotécnica utilizando ferramenta geoestatísticas que, numa segunda fase, é convertida em informação relativa aos parâmetros geomecânicos do maciço rochoso. Uma terceira fase da metodologia considera a seleção das realizações representativas para utilizar na análise numérica. Por fim, os modelos numéricos do maciço rochoso são importados para o software de diferenças finitas onde é efetuada uma análise do comportamento mecânico da estrutura geotécnica. Estes resultados são comparados com os obtidos quando considerada uma abordagem determinística que assume o maciço rochoso como um meio homogéneo. Na validação da metodologia foram utilizados dois casos de estudo, um depósito de outro chileno e o complexo hidroelétrico de Salamonde II, contruído recentemente no norte de Portugal. No que concerne à metodologia para otimizar os planos de prospeção, foram utilizadas a mesmas técnicas geoestatísticas para a simulação do maciço rochoso e assim definir métricas de avaliação da incerteza a utilizar no processo de otimização que utiliza o algoritmo Simulated Annealing. A aleatoriedade inerente à definição dos locais de sondagens foi o ponto de partida para o desenvolvimento de uma segunda metodologia que pretende ser uma ferramenta de apoio aos profissionais da área. Como output são obtidos os locais ótimos para a execução de novas sondagens, assim como os seus comprimentos com o objetivo de reduzir a incerteza associada ao modelo numérico do maciço rochosos e aumentar o detalhe geotécnico. É importante referir que os casos de estudo já mencionados também são utilizados na validação desta metodologia.This research work has been developed in the scope of the Doctoral Programme in Civil Engineering, at the University of Minho, Portugal, and fully supported by the Portuguese Science and Technology Foundation (FCT), under grant no. SFRH/BD/89627/2012

Theory and Practice of Tunnel Engineering

Tunnel construction is expensive when compared to the construction of other engineering structures. As such, there is always the need to develop more sophisticated and effective methods of construction. There are many long and large tunnels with various purposes in the world, especially for highways, railways, water conveyance, and energy production. Tunnels can be designed effectively by means of two and three-dimensional numerical models. Ground–structure interaction is one of the significant factors acting on economic and safe design. This book presents recent data on tunnel engineering to improve the theory and practice of the construction of underground structures. It provides an overview of tunneling technology and includes chapters that address analytical and numerical methods for rock load estimation and design support systems and advances in measurement systems for underground structures. The book discusses the empirical, analytical, and numerical methods of tunneling practice worldwide

Geomechanical behaviour of laminated, weak roof strata and development of an appropriate reinforcement strategy

The work presented in this thesis has been concerned with investigation of the geomechanical behaviour of laminated weak roof strata along longwall roadways in underground coal mines and the mechanisms for effective reinforcement. Field investigations have been particularly associated with underground conditions at Angus Place Colliery, New South Wales, Australia. The principal objectives of this investigation are to understand the deformation behaviour of the laminated weak roof strata and the roof reinforcement problems which have plagued longwall roadway support and underground mining in West Coalfield of New South Wales. Based on the comprehensive engineering understanding of the geomechanical behaviour of laminated weak roof strata, an appropriate reinforcement strategy is developed. The thesis consists of four major parts associated with different approaches adopted in conducting the investigation, including: 1. Laboratory investigation: Conventional deformation and strength parameters of major roof rocks, such as, coal, mudstone and sandstone, including modulus of elasticity, uniaxial compressive strength, (UCS), uniaxial tensile strength, cohesion and angle of internal friction, along with shear strength, triaxial compressive strength with different confinements, have been conducted, in order to determine the mechanical properties of roof rock masses. On the other hand, a series of tests has been conducted to investigate the water sensitivity of mechanical properties of roof rocks, in order to evaluate the effect of water on mechanical properties of roof rocks and to determine the deterioration mechanism of roof rock. According to the results, the intact roof rocks can be classified from medium strong to weak rock mass subjected to the 0% water content. When the water content and discontinuity have been taken into consideration, the roof and floor strata in maingate 22, Angus Place Colliery can be classified as a weak strata. In general, the mechanical properties of surrounding rock masses, the integrity of roof and floor structures are significantly influenced by discontinuity and water. 2. Mine site investigation: The major purposes of this work are to determine the detailed roof deformation behaviour and roof layer separation in the roof strata and the performance of rock bolting reinforcement system used in longwall roadway by using the wire and sonic extensometers and instrumented bolts. According to this work, the roof deformation is differentiated into three different stages associated with different mining activities, that is: a) stage of development, b) stage of time dependent deformation (after development and before extraction) and c) stage of extraction. On the other hand, the deformation behaviour at different horizons associated with different roof geological settings is also determined. Correspondingly, the rock bolting performance is monitored including the maximum axial load, the distribution of load along the length of bolt, the bending moment of bolts as well as the load variation with different stages during the mining. 3. Parametric study: The parametric study is conducted by two and three dimensional computer modelling using Map3D and Phase2. Three dimensional modelling determines the stress redistribution and deformation around opening after roadway development and during the longwall extraction, which provides basic stress parameters as reference for the two dimensional modelling. In two dimensional modelling, the comprehensive parametric study on rock bolting reinforcement system and grouting reinforcement has been conducted. It is noted that the roof stability can be improved through three different ways, which are: a) optimising combination of rock bolting parameters, such as, bolt length, pretension, inclination, stiffness, distribution, etc, b)using combined reinforcement methods, such as, rock bolting and grouting reinforcements, c) altering geometry of opening, particularly for the rectangular shape of opening. 4. Theoretical analyses: The principles of material and structural mechanics have been used and based on these mechanical theories, the roof deformation mechanisms have been developed associated with different stages of mining activities. Based on the outcomes of the study, the reinforcement strategy has been developed using three approaches, including, a) the features of underground geological and geomechanical conditions and deformation behaviour of opening, b) the reinforcement methods and parameters, and c) Principles of New Austrian Tunnelling Method (NATM). Also, the procedure for development of reinforcement strategy has been proposed which can be used as a guide for evaluating the deformation behaviour and developing the reinforcement strategy under different adverse ground conditions