The Experts below are selected from a list of 570 Experts worldwide ranked by ideXlab platform
John Hadjigeorgiou - One of the best experts on this subject based on the ideXlab platform.
-
Quantifying the Impact of Bolting Patterns on the Performance of Welded Wire Mesh
Geotechnical and Geological Engineering, 2020Co-Authors: Efstratios Karampinos, John HadjigeorgiouAbstract:Ground support in underground excavations is typically comprised of surface support and Rock Reinforcement elements. The performance of a ground control system is controlled to a large degree by the interaction between Reinforcement and surface support elements. There is significantly less information on the behaviour of surface support compared to Rock Reinforcement under load. The main source of technical information is through laboratory testing. These investigations however are not standardised and only provide information for limited testing configurations. In this respect, numerical modelling can be used as a complementary and in many cases more robust approach to look at mesh performance under different loading conditions. A prerequisite for this approach is to demonstrate the ability to successfully emulate the mechanical behaviour of bolted wire mesh using numerical models. This paper reports on numerical experiments aiming to reproduce the observed behaviour of bolted welded wire mesh in well documented laboratory tests. The distinct element method was used to construct a series of 3D numerical models to investigate the influence of bolting pattern on the performance of mesh. The developed models successfully captured the load, displacement, and failure of welded wire mesh of multiple wire diameters and demonstrated the impact of the bolting pattern on the loading characteristics and deformation of welded wire mesh. This provides confidence in using the developed numerical tools to further investigate the impact of bolting patterns on the mechanical behaviour of mesh. This would result in valuable information for the optimization of ground support strategies in underground excavations.
-
Explicit Reinforcement models for fully-grouted rebar Rock bolts
Journal of Rock Mechanics and Geotechnical Engineering, 2017Co-Authors: Navid Bahrani, John HadjigeorgiouAbstract:Abstract This paper investigates the explicit use of Rock Reinforcement in a discontinuous stress analysis model. A series of numerical experiments was undertaken to evaluate the performance of local and global Reinforcement models implemented in universal distinct element code (UDEC). This was made possible by calibrating the Reinforcement models to the laboratory behavior of a fully-grouted rebar bolt tested under pure pull and pure shear loading conditions. The model calibration focuses on matching different loading stages of the force–displacement curve including the initial elastic response, the hardening behavior and the bolt rupture. The paper concludes with a discussion on the suitability of the different Reinforcement models in UDEC including their advantages and limitations. Finally, it addresses the choice of input parameters required for a realistic simulation of fully-grouted rebar bolts.
-
A Critical Assessment of Dynamic Rock Reinforcement and Support Testing Facilities
Rock Mechanics and Rock Engineering, 2011Co-Authors: John Hadjigeorgiou, Yves PotvinAbstract:A major engineering challenge for mines experiencing significant seismicity is the performance of the support systems. This paper provides a critical review of dynamic testing techniques used for understanding and quantifying the performance of ground support systems. This review focuses on testing rigs in Canada, Australia and South Africa. The different laboratory testing rigs are listed along with their characteristics and their advantages and disadvantages. The paper concludes with recommendations towards developing a more unified strategy to understand and eventually forecast the behaviour of support systems under dynamic loads.
-
Towards a better understanding of squeezing potential in hard Rock mines
Mining Technology, 2011Co-Authors: Frederic Mercier-langevin, John HadjigeorgiouAbstract:A significant number of underground hard Rock mines have to struggle to maintain and keep operational excavations in squeezing ground conditions. This can often result in considerable investment in Rock Reinforcement and support and in time‐consuming and possibly hazardous scaling and rehabilitation. The LaRonde Mine in Canada has reported squeezing conditions in geological conditions ranging from weak to hard Rock. This paper reports on the development of a ‘Hard Rock Squeezing Index’ based on case studies reported from several mining operations and calibrated based on in situ observations from the LaRonde Mine. The Hard Rock Squeezing Index is based on the foliation spacing of the Rock mass and the stress to intact Rock strength ratio. This index further incorporates the influence of excavation orientation with regard to structure in order to provide an indicator of squeezing potential.
Netra Gurung - One of the best experts on this subject based on the ideXlab platform.
-
1 d analytical solution for extensible and inextensible soil Rock Reinforcement in pull out tests
Geotextiles and Geomembranes, 2001Co-Authors: Netra GurungAbstract:Abstract Performance of any geo-Reinforcement support depends on the efficiency of the tensile stress transfer mechanism. Reinforcement supports against tension in soils and Rock masses are checked for the strength, integrity and effectiveness of the system usually by means of pull-out tests. Although extensive researches were conducted in soil as well as Rock media over the past decades to understand the interaction mechanism, the tensile stress transfer by shear mechanism along the Reinforcement length and non-linear load deformation behaviour still remains a complex analysis. This paper presents a simple 1-D expression for pull-out of planar Reinforcement that is capable to analyse small to large strain cases of inextensible to extensible Reinforcements. The pull-out expressions for highly extensible Reinforcements and for Rock-bolts are presented. In case of soil Reinforcements, it was necessary to use finite difference approximation and Gauss–Seidel iterations to solve the resulting non-linear differential equations. Comparative analyses of Rock-bolts and soil-Reinforcements in pull-out tests with a simplified theoretical prediction are illustrated. Literature reviews on Rock-bolt Reinforcements is referenced to show the similarity on the theoretically derived expressions. The geotechnical evaluation for the modulus of elasticity is also tabulated. Typical Rock-bolt pull-out tests of the Lam Ta Khong Pumped Storage project, Thailand and geosynthetics field/lab pull-out experiments were selected to verify the proposed theory. The predictions based on the proposed theoretical model compare well with the available pull-out test results of Rock-bolts, geotextiles, polymer geosynthetics, and inextensible steel straps.
-
1-D analytical solution for extensible and inextensible soil/Rock Reinforcement in pull-out tests
Geotextiles and Geomembranes, 2001Co-Authors: Netra GurungAbstract:Abstract Performance of any geo-Reinforcement support depends on the efficiency of the tensile stress transfer mechanism. Reinforcement supports against tension in soils and Rock masses are checked for the strength, integrity and effectiveness of the system usually by means of pull-out tests. Although extensive researches were conducted in soil as well as Rock media over the past decades to understand the interaction mechanism, the tensile stress transfer by shear mechanism along the Reinforcement length and non-linear load deformation behaviour still remains a complex analysis. This paper presents a simple 1-D expression for pull-out of planar Reinforcement that is capable to analyse small to large strain cases of inextensible to extensible Reinforcements. The pull-out expressions for highly extensible Reinforcements and for Rock-bolts are presented. In case of soil Reinforcements, it was necessary to use finite difference approximation and Gauss–Seidel iterations to solve the resulting non-linear differential equations. Comparative analyses of Rock-bolts and soil-Reinforcements in pull-out tests with a simplified theoretical prediction are illustrated. Literature reviews on Rock-bolt Reinforcements is referenced to show the similarity on the theoretically derived expressions. The geotechnical evaluation for the modulus of elasticity is also tabulated. Typical Rock-bolt pull-out tests of the Lam Ta Khong Pumped Storage project, Thailand and geosynthetics field/lab pull-out experiments were selected to verify the proposed theory. The predictions based on the proposed theoretical model compare well with the available pull-out test results of Rock-bolts, geotextiles, polymer geosynthetics, and inextensible steel straps.
E. Villaescusa - One of the best experts on this subject based on the ideXlab platform.
-
Case Studies of Rock Reinforcement Components and Systems Testing
Rock Mechanics and Rock Engineering, 2014Co-Authors: A. G. Thompson, E. VillaescusaAbstract:Rock Reinforcement is widely used in tunnels and surface and underground mines. A large number of proprietary products are available in various configurations of components. While the mechanical properties of the primary element are available from product brochures, the associated component properties may vary widely and adversely influence the overall performance of the system. Field pull out tests are most commonly used to measure the system response in the toe anchor region. However, the response of the collar region is less commonly considered but may be more important. Several case studies are described in which various components and systems of Rock bolts and cable bolts have been subjected to static loading in the laboratory and in the field. The results generally demonstrate the importance of considering the properties of all the components and not simply those of the primary element. In some cases, the internal fixtures have strengths much less than the elements. Often it has also been found that the fixture at the collar has significantly less strength than the element and this will result in complete loss of function in restraining surface support hardware, such as plates, mesh and reinforced shotcrete.
-
A Reinforcement design methodology for highly stressed Rock masses
2014Co-Authors: E. Villaescusa, John Player, Alan ThompsonAbstract:Ground support design is usually based on previous experience and evolves over a number of years. As the Rock mass conditions change with an increasing depth, the ground support performance may change and become unacceptable. That is, the installed Reinforcement capacities may not satisfy the Rock mass demand. A methodology that allows Rock Reinforcement design for highly stressed Rock masses where Rock mass demand in terms of ranges of displacement and energy is compared with the WA School of Mines Reinforcement capacity database is presented. It is concluded that acceptable bolts for a particular mining condition should have displacement compatibility with the Rock mass, while providing higher energy dissipation.
-
Ground Support Terminology and Classification: An Update
Geotechnical and Geological Engineering, 2012Co-Authors: A. G. Thompson, E. Villaescusa, C.r. WindsorAbstract:It is nearly two decades since a formal terminology and a classification scheme were proposed for Rock Reinforcement hardware and applications. That combined framework was used to clearly identify concepts associated with Reinforcement mechanics in a manner that was consistent and robust enough to characterise all Reinforcement systems. Since that time, many new Reinforcement systems have been developed and it can be shown that they all fit within the proposed classification scheme. Most recently, a complementary new terminology and a classification scheme for surface support, also based on mechanics, have been developed. This framework is invaluable in the design of ground support schemes, the planning of testing and instrumentation programs and the development of software used to simulate the static and dynamic response of Rock Reinforcement and support systems. It will be shown that the terminology and classification schemes are valid today and will so remain into the future because of the laws of mechanics.
-
Monitoring the performance of Rock Reinforcement
Geotechnical & Geological Engineering, 1999Co-Authors: E. Villaescusa, C.j. SchubertAbstract:A Rock mechanics program has been developed and implemented in order to achieve a safe and economical room and pillar extraction of the shallow dipping orebodies at the McArthur River Mine in Australia. Three closely spaced tabular orebodies have been targeted for extraction over the life of the mine and due to economics the lowermost number 2 orebody is being mined first. This paper formulates the calculation of the 2 Orebody hangingwall spans and the appropriate Rock Reinforcement design for the long-term stability of the room and pillar excavations. The field trials suggested that a Rock beam was formed within the hangingwall of the room and pillar operations, arresting any vertical movement of the roof. The results indicated that the weight of the beam is transferred to the pillars via an arching process and there is no need for deep-anchored Reinforcement.
Yves Potvin - One of the best experts on this subject based on the ideXlab platform.
-
A Critical Assessment of Dynamic Rock Reinforcement and Support Testing Facilities
Rock Mechanics and Rock Engineering, 2011Co-Authors: John Hadjigeorgiou, Yves PotvinAbstract:A major engineering challenge for mines experiencing significant seismicity is the performance of the support systems. This paper provides a critical review of dynamic testing techniques used for understanding and quantifying the performance of ground support systems. This review focuses on testing rigs in Canada, Australia and South Africa. The different laboratory testing rigs are listed along with their characteristics and their advantages and disadvantages. The paper concludes with recommendations towards developing a more unified strategy to understand and eventually forecast the behaviour of support systems under dynamic loads.
A. G. Thompson - One of the best experts on this subject based on the ideXlab platform.
-
Case Studies of Rock Reinforcement Components and Systems Testing
Rock Mechanics and Rock Engineering, 2014Co-Authors: A. G. Thompson, E. VillaescusaAbstract:Rock Reinforcement is widely used in tunnels and surface and underground mines. A large number of proprietary products are available in various configurations of components. While the mechanical properties of the primary element are available from product brochures, the associated component properties may vary widely and adversely influence the overall performance of the system. Field pull out tests are most commonly used to measure the system response in the toe anchor region. However, the response of the collar region is less commonly considered but may be more important. Several case studies are described in which various components and systems of Rock bolts and cable bolts have been subjected to static loading in the laboratory and in the field. The results generally demonstrate the importance of considering the properties of all the components and not simply those of the primary element. In some cases, the internal fixtures have strengths much less than the elements. Often it has also been found that the fixture at the collar has significantly less strength than the element and this will result in complete loss of function in restraining surface support hardware, such as plates, mesh and reinforced shotcrete.
-
Ground Support Terminology and Classification: An Update
Geotechnical and Geological Engineering, 2012Co-Authors: A. G. Thompson, E. Villaescusa, C.r. WindsorAbstract:It is nearly two decades since a formal terminology and a classification scheme were proposed for Rock Reinforcement hardware and applications. That combined framework was used to clearly identify concepts associated with Reinforcement mechanics in a manner that was consistent and robust enough to characterise all Reinforcement systems. Since that time, many new Reinforcement systems have been developed and it can be shown that they all fit within the proposed classification scheme. Most recently, a complementary new terminology and a classification scheme for surface support, also based on mechanics, have been developed. This framework is invaluable in the design of ground support schemes, the planning of testing and instrumentation programs and the development of software used to simulate the static and dynamic response of Rock Reinforcement and support systems. It will be shown that the terminology and classification schemes are valid today and will so remain into the future because of the laws of mechanics.
