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Abstract: An ISRM Commission on Underground Research Laboratory (URL) Networking was formed in 2011 for better exchanges of information among different societies, academia, laboratories, and industry on underground studies. The Commissioners have interests in radioactive waste assessments, energy and environment evaluations, and physics rare event detections. Workshops, professional society meetings, and literature surveys are currently means for the Commission to address its scope. There are URLs established along roadway tunnels, dedicated facilities excavated, and borehole complexes drilled/tested for energy and environmental assessments. Thus networking will allow defining the most complementary experiments to isolate the high diversity of effects in heterogeneous medium of interests to the rock mechanics community. In this article, we report some preliminary findings from our recent efforts since 2011. For example, the American Geophysical Union 2012 annual meetings have sessions organized on energy and resource recovery, underground studies, and natural hazard related interactions. Some discussions of interactions among geophysics, rock mechanics, petroleum geomechanics, and mining engineering were initiated. We discuss specifically how LSBB and potential other URLs provide testing platforms for the observation of faulting in weak and tight materials. A suggested testing method has been proposed for a pulsed and stepped test sequence to be applied in the field, with the method using the High Pulse Poroelasticity Protocole - an injection and measuring device for hydromechanical testing in packed borehole intervals at depths. Such approach could allow the in situ studies of static to dynamic frictional behaviors of large scale heterogeneities that are poorly described in conventional laboratories.
- Europe (1.00)
- Asia > China (0.81)
- North America > United States > California > San Francisco County > San Francisco (0.31)
- Geology > Rock Type (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.89)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (0.69)
- Health, Safety, Environment & Sustainability > Environment > Waste management (0.68)
ABSTRACT This paper on the 50-year anticipated future of the ISRM and rock mechanics forms part of the ISRM 50-year anniversary celebrations and complements the preceding paper by ET Brown in these proceedings on the previous 50 years of the ISRM. The current status of rock mechanics and the unsolved problems are summarisedโso that the results of extrapolating our current capabilities can be considered. The problems are noted under the headings of geology, rock stress, intact rock, fractures, water flow, modelling and design. The anticipated future developments are then highlighted under the headings of information access, site investigation, subject integration, international co-operation, โintelligentโ computer programs, increased excavation speed and larger excavations, environmental aspects, the future of the ISRM itself, and the implications of future computing power. It is predicted that the greatest changes to rock mechanics and the ISRM itself will result from the continuing growth in computing power.
- Well Drilling > Wellbore Design (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
ABSTRACT The continuing development of sophisticated numerical modelling tools, especially discrete element analysis, has made possible improved representation of rock mass features during computer simulation. In particular, all the โDIANEโ features of rock can now be incorporated into such analyses, i.e. discontinuities, in homogeneity, anisotropy and non-elastic behaviour. However, in order for the simulations to validly represent the in situ rock mass, it is essential that the geological nature and structure of the rock mass are understood and incorporated in the modelling. We discuss this structural geology contribution to rock mechanics in the context of geological structures, fractures, water flow, scale, and modelling, plus rock engineering design.
- Asia > China (0.30)
- Europe > United Kingdom (0.28)
- Geology > Structural Geology (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.47)
- Asia > China > Xinjiang Uyghur Autonomous Region > Tarim Basin (0.99)
- Europe > United Kingdom > England > London Basin (0.91)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Well Drilling > Wellbore Design > Rock properties (0.90)
ABSTRACT As part of the preparations for the design of an underground repository for radioactive waste at Posiva's site on the west coast of Finland, there has been considerable site investigation work. One of the key elements of this work has been the estimation of the in situ stress field and determination of the mechanical properties of the crystalline rocks present. The stress field is required as the boundary condition for numerical modelling and to determine a suitable orientation for the repository tunnels. The mechanical rock properties are required, inter alia, to establish whether there is any potential for rock spalling at the ca. 400โ450 m anticipated depth of the repository. A key aspect of the analysis is the understanding of the in-situ spalling strength in order to be able to predict the spalling potential, not only during deposition tunnel and deposition hole excavation but also in the longer term when the rock mass is subjected to canister heating up to temperatures close to 60 ยฐC. The in situ spalling strength is of the order of 60% of the uniaxial compressive strength. Accordingly, an in situ rock mechanics experiment has been designed and conducted in a niche tunnel off the main ONKALO ramp at the Olkiluoto site in Finland. The experiment has the acronym POSE: Posiva's Olkiluoto Spalling Experiment. The experiment has involved the drilling of two closely located full-scale simulated deposition holes, 1.524m in diameter, which concentrate the in situ stress and enable rock spalling to be observed at close hand. In addition, heaters have been used to simulate the rock temperature increase due to radioactive canister heat generation, further altering the in situ stress field. The preliminary POSE experimental results and the thermo-mechanical simulations are illustrated and presented in this paper.
- Energy > Oil & Gas > Upstream (0.69)
- Water & Waste Management > Solid Waste Management (0.49)
- Energy > Power Industry > Utilities > Nuclear (0.49)
- Well Drilling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
Abstract For the engineering design of underground structures in rock masses, knowledge of the natural in situ stress state is generally requiredโas basic information and as input to numerical programs supporting the design. This review paper covers the relevant key points, including the nature of in situ stress, the relation between structural geology and rock mechanics and engineering, rock stress measurement/estimation, the ISRM Suggested Methods for rock stress estimation, rock stress compilations, the influence of free surfaces on rock stress (including the Excavation Disturbed Zone and rock spalling), and other perturbations of the rock stress field, including a mention of the effect of natural voids in karst regions.
- Europe > Switzerland (0.28)
- North America > United States (0.28)
- Europe > Belgium (0.28)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.69)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Abstract The future for rock mechanics and the International Society for Rock Mechanics (ISRM) is considered by assessing what has been achieved in the first 50 years of rock mechanics and hence identifying some of the major remaining unsolved problems. By noting the direction that technology might take in the future, the possibilities for future rock mechanics developments are also considered. The near-future encompasses the current ISRM modernization programme that the Board is implementing and developments that are clear from known technology. The further-future is predicted from likely technological innovations and their implications for rock mechanics. Additionally, the purpose, nature and potential evolution of professional societies such as the ISRM are briefly discussed. The emphasis in this paper is on rock mechanics as it supports rock engineering, the subjects cove 1. Introduction It is important for our subject of rock mechanics and its application to rock engineering that we consider the directions that are likely to be taken in the future. Indeed, this is a suitable time for such speculation as the 50-year anniversary of the founding of the ISRM is due in 2012, with the celebrations beginning at the 2011 ISRM Congress in Beijing. Additionally, this year, 2008, is the centenary of Leopold Mueller's birth, the founder and first President of the ISRMred being geology, rock stress, intact rock, rock fractures, water flow, engineering activities and numeri So, in this paper, and based on what has been achieved in the past (essentially over the last 50 years), let us identify some of the major remaining problems that have not yet been solved. This leads naturally to the consideration of which technological developments are likely in the future and hence whether these will enable the remaining problems to be solved. In terms of the ISRM, there is currently a major modernisation underway which will, to some extent, enable a prediction of the near future for the ISRM. However, the far future for the ISRM will also be discussed because this encompasses interesting questions relating to the nature of individual and group interactions and the storage and dissemination of corporate knowledge. 2. Summarising the Current RockMechanics Knowledge and Capabilities The rock mechanics knowledge and capabilities have been summarized in encyclopaedic form vi Rock Engineering" which was produced by Elsevier in 1995 [1]. The five volumes cover the subjects of: 1. Fundamentals 2. Analysis and Design Methods 3. Rock Testing and Site Characterisation 4. Excavation, Support and Monitoring 5. Surface and Underground Case Histories. Although it is now 13 years after this compendium was published and advances have been made in many areas, the essence of the state. 3. Unsolved Problems in Rock Mechanics Despite the major progress that has been made in rock mechanics and rock engineering over the last 50 years, there are still outstanding problems. In fact, Leopold Muller's motivation for founding the ISRM was encapsulated in his May 1962 comment, "We don't know the rock mass strength. That is why we need an International Society.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics (0.46)
- Well Drilling > Wellbore Design > Rock properties (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
Numerical Experiment Model For Heterogeneity Rock Specimens
Wang, S.H. (CRISR, School of Resource and Civil Engineering, Northeastern University) | Tang, C.A. (CRISR, School of Resource and Civil Engineering, Northeastern University) | Xu, T. (CRISR, School of Resource and Civil Engineering, Northeastern University) | Hudson, J.A. (Imperial College and Rock Engineering Consultants, 7 The Quadrangle)
ABSTRACT A numerical parameter-sensitivity analysis has been conducted to evaluate the effect of heterogeneity on the fracture processes and strength characterization of rock under uniaxial compression loadings. The deformation mechanisms of rock under different constant confining pressures was briefly analyzed based on Continuum damage mechanics and the effect of confining pressure on deformation, strength and macroscopic fracture patterns of model rock specimens are also studied using Rock Failure Process Analysis (RFPA) code, that show the nucleation and growth of macrocracks in relatively heterogeneous specimens under uniaxial loading. In this simulator, the heterogeneity of rock is considered by assuming that the material properties of elements conform to Weibull distribution, an elastic damage-based law that considered the strain-rate dependency is used to describe the constitutive law at mesoscopic scale, and finite element program is employed as a basic stress analysis tool. The theoretical analysis and numerically obtained results duplicate the deformation, strength (such as Young's modulus, compressive strength, etc) and macroscopic fracture patterns observed in laboratory. While the details of macrocrack formation varied from specimen to specimen, a number of features were consistently obtained in the numerical simulations. The theoretical studies and numerical simulations are extremely instructive and indicative for investigating some catastrophic hazard phenomena such as rock bursts, instability induced by excavation. Splitting and faulting failure modes often observed in experiments are also observed in the simulations under uniaxial compression. It is found that tension fractures are the dominant failure mechanism in both splitting and faulting processes. The numerical simulation shows that faulting is mainly a process of tensile fractures, often en echelon fractures, developed in a highly stressed shear band, just is as observed in actual Uniaxial compression tests. In these simulations, the same diffused AE events or micro fractures but with higher count number also appeared in the early stage of loading. INTRODUCTION The uniaxial compressive strength of a rock is one of the simplest measures of strength. It may be regarded as the largest stress that a rock specimen can carry when a unidirectional stress is applied to the ends of a specimen. In other words, the unconfined compressive strength represents the maximum load supported by the specimen during the test divided by the cross sectional area of the specimen. Although the utility of the compressive strength value is limited, the unconfined compressive strength allows comparisons to be made between rocks and provides some indications of rack behavior under more complex stress systems. Experimentally, researchers have undertaken the task of loading specimens to obtain better knowledge of the compressive failure mechanisms and considerable discussion has been devoted in the literature to this test method (Pells,1993; Wawersik etc,1970; Wawersik & Brace,1971; Lockner DA, et al.,1992; Lockner & Byerlee,1991; Cox & Meredith,1993; Blair & Cook,1998;etc.). Though this mode of failure has been studied in detail for decades, the details of the failure mechanisms, including the microfracture initiation, propagation, coalescence, axial splitting, shearing, etc., are not fully understood and still remain the subject of considerable scientific interest.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics (0.46)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (0.89)
ABSTRACT Given the current widespread use of numerical models for rock mechanics and rock engineering, and the โTechnology Road Mapโ theme of the Congress, it is timely to consider the key issues in matching numerical models to rock engineering problems. The three main aspects are:identifying the mechanisms, variables and parameters that are relevant to a particular rock engineering project; establishing the content and mode of operation of a particular code; and deciding whether a particular code provides an adequate model for a particular project. We summarise the key issues, highlighting the concept of rock mass domains, validation and the ability to present the results of a modelling exercise. We include three compact numerical modelling case examples to illustrate the points. Finally, we also present a โroadmapโ to assist in the process of matching a numerical model to the rock reality. RESUME Considerant l'utilisation generalisee des modรจles numeriques en mecanique des roches et en ingenierie au rocher ainsi que le thรจme du congrรจs 'technology road map', il est opportun d'aborder les problรจmes essentiels lies au choix des modรจles numeriques dans les problรจmes ingenierie au rocher. Les trois aspects principaux sont:l'identification des mecanismes, variables et paramรจtres appropries au projet considere, la definition du contenu et du mode de fonctionnement d'un code numerique donne, et la possibilite de decider si un code donne fourni un modรจle approprie au projet considere. Les points cles sont resumes en mettant en evidence les notions de "massif rocheux", de validation et de capacite ร presenter les resultats d'une approche numerique. Nous presentons trois brรจves etudes de cas qui illustrent ces points. Enfin, nous proposons aussi un logigramme pour aider au choix d'un modรจle numerique approprie pour representer la realite d'un problรจme au rocher. ZUSAMMENFASSUNG Im Licht der augenblicklich weitverbreiteten Nutzung von numerischen Modellen in der Felsmechanik and im Felsingenieurbau und unter Beruecksichtigung der Themenstellung des Congresses "Technology Road Map", erscheint es an der Zeit die Kernprobleme, die sich mit Fragen der Abstimmung der numerischen Modele mit Hinblick auf ihre Anwendbarkeit im Felsingenieurbau beschaeftigen, naeher zu befassen. Die drei wesentlichen Aspekte sind:Identifizierung der Mechanismen, Variablen und Parameter, die fuer ein bestimmtes Projekt im Felsingenieurbau von Bedeutung sind; die Festlegung des Inhalts und des Modus Operandi eines bestimmten Codes, und die Entscheidung darueber ob ein bestimmter Code ein hinreichendes Model fuer ein bestimmtes Projekt ergibt. Wir fassen die wichtigsten Punkte zusammen, heben dabei das Concept der Gesteinsmassen Domaenen (Rock mass domains) hervor, und erarbeiten ihre Beurteilung und die Moeglichkeit diese zu praesentieren in den Ergebnissen einer Model Uebung. Wir schliessen drei Beispiele von numerischen Modellen ein in denen diese Punkte erlauetert werden. Zuletzt schlagen wir eine "Roadmap" vor, um dem Prozess der Abstimmung des numerischen Modells mit der "Felsmechanischen Wirklichkeit" zu unterstuetzen. Introduction One of the greatest advances in rock mechanics analysis and rock engineering design in recent years has been the development of a number of powerful numerical codes that simulate various aspects of the deformation and failure of rock masses. These codes enable studies to be made of the evolution of rock failure for different rock mass characteristics, different construction geometries and different loading conditions. Modern codes can incorporate many of the discontinuous, inhomogeneous, anisotropic and โnot elasticโ (DIANE) characteristics of real rock masses. Nevertheless, practising engineers are faced with the problem of knowing which code is most appropriate for their purposes, and whether the results produced by the code are, indeed, representative of reality at their site. This is an outstanding problem in rock mechanics and rock engineering. So, how is the modeller and/or engineer to find a design pathway through the well-mapped subject areas of precedent practice projects and the terra incognita of non-precedent practice projects for any given project objective? In order to be able to coherently design an underground structure in a rock mass, the engineer must be able to predict the consequences of different design options.
- Well Drilling > Wellbore Design (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
ABSTRACT: In order to be able to implement a procedure for checking the adequacy of rock mechanics modeling and rock engineering design, the technical auditing approach has been developed. This is a procedure for formally examining modeling and design to ensure that they have captured the essence of the problem in hand. The main subject areas in rock mechanics are reviewed and the modeling problems highlighted. A range of engineering projects is listed to illustrate the wide variety of engineering objectives and associated issues. The principles of technical auditing are presented and a case example included to illustrate the required supporting information and documentation. Technical auditing can be used 'before the event' to guide the modeling and design or 'after the event' to check that a model or a design has indeed addressed the technical objectives and included those variables, mechanisms and parameters required to represent the rock reality. The audit trail provides transparency and traceability for modeling and design. INTRODUCTION The theme of Vail Rocks '99 is 'Rock Mechanics for Industry' with the intention of "promoting dialog and exchange between academia and practice in various aspects of rock mechanics, rock engineering and geological engineering". Rock mechanics can be studied without reference to any application, and rock engineering can be undertaken without reference to any knowledge, apart from precedent practice. However, as recognized by ARMA and in the context of this Symposium, there is greater value in rock mechanics being studied as an applied subject and in practitioners being aware of the contributions rock mechanics can make to the design of all structures built on or in rock masses. The rock mechanics dialog between academia and industry is required because civil, mining, petroleum and environmental engineers need a predictive capability to support engineering design and construction. Precedent practice, regarded either as a basis for design or as background information, is usually helpful, but cannot be a standalone basis for engineering design when the engineering purpose has changed significantly, or the geology has changed, or the dimensions of the structure have changed, etc. The designer needs to be able to predict the outcome of engineering actions and to assess potential hazards and their consequences. In short, some form of engineering rock mechanics modeling is required, as illustrated in Fig. 1.
- Materials > Metals & Mining (0.94)
- Energy > Oil & Gas > Upstream (0.68)
- Well Drilling > Wellbore Design > Rock properties (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
Stress-Induced Anisotropy In Rock And Its Influence On Wellbore Stability
Wu, B. (Rock Mechanics Group, Department of Mineral Resources Engineering, Imperial College of Science, Technology and Medicine) | Hudson, J.A. (Rock Mechanics Group, Department of Mineral Resources Engineering, Imperial College of Science, Technology and Medicine)
1 INTRODUCTION ABSTRACT: A triaxial test procedure is proposed in this paper to observe and evaluate stress-induced anisotropy in originally isotropic rocks. Preliminary test results on the Springwell sandstone show that an originally isotropic rock becomes anisotropic when subjected to a non-hydrostatic stress. Normally, the deformation modulus of the rock in maximum stress direction is greater than that in minimum stress direction. The implications of stress-induced anisotropy in wellbore stability is demonstrated using closed-form solutions for hollow cylinders. One of the main effects of creating an underground excavation, be it a tunnel or a wellbore, is generally to induce large a tangential stress and a small radial stress. The rock immediately surrounding the excavation is therefore under an extremely non-hydrostatic stress state. Because it is this part of the surrounding rock that is responsible for the instability of the excavation, a better understanding of the mechanical behaviour of a rock under a non-hydrostatic stress state is crucial for the design of the underground excavation. It has long been recognised that the mechanical behaviour of rocks and rock masses is significantly affected by the presence of cracks, joints and fractures. Many authors in geophysics (e.g. Crampin, 1984, 1985; King & Xu, 1989) reported that a rock with an isotropic matrix but which is permeated by aligned cracks or fractures will behave in an anisotropic way. Although many investigations show that a non-hydrostatic stress induces a velocity anisotropy of elastic waves and consequently anisotropy of dynamic elasticity in geo- physics (e.g. Nikitin & Chesnokov, 1984; Crampin, 1984a; Rai & Hanson, 1988; Nur & Simmons, 1969; Sayers, et al., 1990; Wu et al., 1991), little work has been done on stress-induced anisotropic mechanical properties in rock mechanics and rock engineering. Some experimental results from Imperial College in recent years have shown that the Young's modulus can be interpreted as being dependent on the minimum compressive stress, e.g. the confining pressure (Santarelli, 1987). It has been reported that an isotropic pressure-dependent Young's modulus model, formulated based on triaxial test results, improved predictions of stress distributions around a borehole, compared to a linear elastic model (Santarelli et al., 1986; Mclean, 1988). Furthermore, more recently experimental work on hollow cylinders showed that a radially anisotropic modulus model is more suitable in interpreting the measured borehole displacements (Ewy & Cook, 1990). In this paper, as a part of an effort to characterize the stress-induced anisotropy, we have proposed a triaxial test procedure to observe and evaluate the effects of a non-hydrostatic stress on originally Isotropie rocks. The preliminary test results on the Isotropie Springwell sandstone showed that the rock is stiffer in the direction of maximum principal compressive stress than in the direction of minimum principal compressive stress. The Young's modulus measured using a conventional triaxial testing procedure is generally the maximum in the axial stress direction. The influences of stress-induced anisotropy on the stress distributions around a wellbore are demonstrated using closed form solutions for hollow cylinders.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.46)
- Well Drilling > Wellbore Design (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)