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Abstract: 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 maybe 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.
- North America > United States (0.30)
- North America > Canada (0.28)
- Geology > Geological Subdiscipline > Geomechanics (0.94)
- Geology > Rock Type (0.69)
- Well Drilling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (0.89)
- Management > Professionalism, Training, and Education > Communities of practice (0.62)
- Data Science & Engineering Analytics > Information Management and Systems > Knowledge management (0.62)
Abstract: Artificial ground freezing continues to prove as an effective approach to successful underground excavations in weak rock mass 11conditions. Numerous mining and civil projects use artificial freezing worldwide; however uncertainties remain with respect to understanding and predicting behavior of frozen rock mass.
- North America > United States (0.93)
- North America > Canada > British Columbia (0.29)
- North America > Canada > Saskatchewan (0.28)
- North America > Canada > Alberta (0.28)
- Geology > Rock Type (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- North America > Canada > Saskatchewan > Myrtle Basin > McArthur Basin > EP 171 > McArthur River Mine (0.99)
- North America > Canada > Saskatchewan > Athabasca Basin (0.99)
- North America > Canada > Alberta > Athabasca Basin (0.99)
- Well Drilling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.71)
Abstract: An enhanced version of the Discrete Element Method (DEM) has been developed for the analysis of fractured rock masses. In addition to the discrete representation of the intact medium, structural defects can be explicitly taken into account in the modeling to represent pre-existing fractures or joints. Besides its intrinsic capability to model fracture initiation and propagation starting from simple interaction laws, the model can simulate brittle behavior characterized by high values of UCS/TS ratio associated with non-linear failure envelopes, as observed for stiff rocks. In the present work, the method is used to study jointed rock slopes where instabilities involve coupled mechanisms related to both deformations along existing discontinuities and brittle fracture of intact rock. In case of complex fracture systems, it is possible to plug discrete fracture networks (DFN) into the model to characterize the mechanical behavior of fractured rock masses by controlling the size distribution of the fractures, their spatial correlation and their intensity.
- North America > United States (0.46)
- Europe > France (0.28)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.69)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (0.55)
Abstract: The technology for the mechanical excavation of low to medium strength rock has been substantially well developed, and therefore it has been used in most cases as an alternative technology to drill and blast excavation (Gertsch, 1994). However, in the case of hard rock excavation, especially for mining excavations, such advancement in the development of an efficient and effective cutting system has not yet been achieved. This is partly because of inadequate understanding of the basic mechanism of rock cutting and partly because of a lack of understanding in the fundamental processes involved in the rock cutting machines. This paper describes one of the advanced cutting technologies called the oscillating disc cutting for hard rock cutting and its advantages over other cutting systems are highlighted by comparing the results with that of conventional disc cutting technique employed in most tunnel-boring machines. The parameters such as oscillating frequency and the rock brittleness on the mean cutting forces are examined and their results are discussed. The experimental results clearly indicated the advantages of the cutting technology in the construction of a lightweight flexible machine for hard rock excavation.
- North America > United States (0.46)
- Oceania > Australia (0.30)
- Well Drilling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.68)
- Well Completion > Hydraulic Fracturing (0.68)
Abstract: Due to the nature of the rock mass strength the stability assessments for the design of the West Big Rock pit walls at pre-feasibility level considered both the rock fabric and the rock mass strength. Kinematic analyses (based on stereographic projections) were conducted to search for potential failures at bench scale, where the rock mass rating was found to be higher than 35-40. Stability analysis using limit equilibrium methods (based on rock mass strength) conducted to search for potential failures at overall pit slope scale. The analyses were based on geotechnical properties and data collected during the subsurface geotechnical programs. Site investigation and preliminary geotechnical design details that incorporate site specific conditions for the proposed West Big Rock pit at Brewery Creek, are discussed in this paper.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology (0.94)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.47)
- Consumer Products & Services > Food, Beverage, Tobacco & Cannabis > Beverages (0.64)
- Materials > Metals & Mining (0.47)
- Energy > Oil & Gas > Upstream (0.47)
- North America > Canada > Yukon > Selwyn Basin (0.99)
- North America > Canada > Northwest Territories > Selwyn Basin (0.99)
Abstract: World-wide mining operations utilize block caving as one of the most cost-effective techniques for ore extraction. Block caving has been addressed in the past by numerous discontinua methods to include Discrete Element Method (DEM), Discontinuous Deformation Analysis (DDA), Combined Finite-Discrete Element Method (FDEM), etc. However, most of these analyses were either limited to 2D or to elastic material representation. In this paper a representative 3D block caving problem is simulated using FDEM. Los Alamos National Laboratoryโs Geophysics team conducted the modeling utilizing their in-house FDEM code, MUNROU. MUNROU is a fully parallel, 2D/3D FDEM code which utilizes material models that account for a number of plasticity effects, as well as has the capability to model explosive effects, irregular shapes and fracture initiation and propagation. Previously problems of this nature and size were un-tractable in 3D. However, the recent performance improvements seen in MUNROU through the implementation of state of the art parallelization algorithms (see Computational Mechanics of Discontinua, Wiley 2011), have prompted our team to begin intensive efforts to address real world problems, such as block caving. The codeโs inherent capability to address fracture and fragmentation processes at laboratory scale level has been consistently proven in the past. In this paper the feasibility of extending MUNROU to large space scales in 3D is demonstrated. With this improved capability it is now expected that future analyses efforts can concentrate on 3D phenomenological considerations such as jointing, frictional fault behavior, etc.
- North America > United States > California (0.28)
- North America > United States > New Mexico > Los Alamos County > Los Alamos (0.25)
- Well Completion > Hydraulic Fracturing (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (0.89)
Abstract: Characterization of the major geological structures (intermediate and overall scale faults/shear zones) is a critical component for developing a model of structural domains for rock slope design in mines in structurally controlled environment. Faults at the proposed EKATI Pigeon Pit site can only be interpreted by drilling information, since there is no outcrop at and around the proposed Pit site. In order to develop a 3D fault model, a technique was needed to determine where faults exist at the proposed Pit area and how they connect between boreholes so that their persistence and orientation could be assessed. In this study, Cumulative Fracture Frequency (CFF) was plotted for the geotechnical drill holes to assist in potential fault identification. Any substantial increase in the cumulative fracture frequency was considered as a potential major fault which later was cross-checked with core photos and the recorded description of infill materials. The identified faults then were used in Gemcom Gemsโข to examine their possible connectivity and to construct a 3D fault model. Based on the estimated length, thickness and orientation of the faults, a qualitative risk assessment was eventually conducted to evaluate the risk associated with each fault. It was perceived from the analysis that 6 faults out of 34 individual faults identified preliminarily from the CFF analysis may present moderate to high risks for potential inter-ramp instability.
- North America > United States (0.93)
- North America > Canada > Northwest Territories (0.47)
- Geology > Geological Subdiscipline (1.00)
- Geology > Mineral > Silicate (0.96)
- Geology > Rock Type > Igneous Rock (0.71)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.46)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (0.96)
- Management > Risk Management and Decision-Making > Risk, uncertainty, and risk assessment (0.69)
Abstract: Because of the potentially problematic conditions created to deep mining or civil projects by adverse fault slip behaviour, assessing what geological structures are under a critical stress state is becoming an increasingly important endeavour. This paper presents common structural geology techniques that are not widely known or regularly applied either for deep civil engineering design or for deep high stress mining, but which can have merit for risk minimization for excavation development. Several techniques are explored and guidelines for using fault mapping data and applying stress inversion approaches are presented for advancing understanding of past and current stress state โ both of which are key to establishing propensity for slip on geological structures.
- North America > United States (1.00)
- Europe (0.67)
- Geology > Structural Geology > Fault (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.47)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Faults and fracture characterization (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Abstract One of safety problems caused by blasts is the dynamic tensile fracture in underground mines. Theoretically, a tensile stress wave from a free surface is the major reason for such dynamic fracture. To confirm this, the paper presents a single shot and production blast tests in LKAB Malmberget mine. The result from the single shot indicates that when a free surface is 8.9 m far from the nearest charge position, the surface is still seriously destroyed, even though it is a decoupled charge. In full charged blastholes, as the free surface is 20 m away from the nearest charge, the spalling is also marked. However, as the delay time was increased from 10 to 30 ms, spalling in the roof disappears, indicating the rock fracture in the roof is controllable. The field investigation indicated that (1) rock fall from the roof of a drift after blasting happened not only close to a blasthole but also far from it; (2) eyebrow break caused by tensile fracture is a common phenomenon in sublevel caving. Finally, the paper introduces some measures to reduce the tensile rock fracture caused by blasts in underground mining. 1 Introduction Blasting plays an extremely important role in mining and rock engineering. On the other hand, blasting causes some negative effects on mining safety and environment. For example, blasting usually induces rock break or fracture in and near the surface of a tunnel or a drift in underground mines. In sublevel caving mining, such rock break usually appears in the roof and wall of a production drift or other rock structures (Zhang, 2005; 2011). Blasting can cause rock fall from the roof of a drift or tunnel, even though the place of rock fall may be far from the blastholes. Blasting may also initiate a seismic event (Eremenko et al., 2009). All the above phenomena are dynamic rock fracture problems caused by blasts. On this background we will first analyze dynamic fracture near a free surface, often called spalling. Then we will show different types of dynamic rock fracture in sublevel caving and discuss the measures to handle the problems.
- Well Completion > Hydraulic Fracturing (0.57)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (0.34)
Method to Simulating Cracking of Surrounding Rock in Coal Mines
Xue, Yuting (State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences) | Liu, Quansheng (State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences) | Lu, Xingli (College of Civil Engineering and Architecture, Wuhan University)
Abstract Due to the stress redistribution after excavation, the pre-existent joints or cracks will deform and new cracks will initiate and propagate in surrounding rock, especially in the plastic zone. And differences, once cracks initiate and propagate in a certain area, exist when the equivalent continuum mechanics and non-continuum mechanics are used to analyze its mechanical response. A method is proposed in this paper to approximately simulate continuum before cracking and to change the potential joints to joints after cracking beginning which can approximately take the effects of cracking into consideration. And this method is explained, in detail, from its computation procedure, the determination of initial material parameters, the distribution of potential cracks and the failure criteria for the real and potential joints. Finally, two sets of numerical analyses are made to verify its effectiveness in approximately simulating continuum and the cracking process. Introduction After the excavation of roadways, the stress in surrounding rock, according to the solution of Elasticity, will range from in-situ stress far away to zero at the surface of the roadway in the radial direction. It means that the excavation brings about unloading for the surrounding rock in radial direction. This stress redistribution will definitely promote the generation of cracks. And the area with cracks is different from that without cracks, especially considering the dilatancy caused by the slip along a persistent cracks and the opening of cracks resulted from the unloading in surrounding rocks. The effects of cracking should be considered to achieve better analysis of the stability of roadways. Nowadays, there are two ways to take the effects of cracking into consideration: the equivalent continuum mechanics and the non-continuum mechanics. To achieve that, the equivalent continuum mechanics method considers the discontinuous rock mass as a continuous medium and the effects of cracking will be reflected by the reduction of strength parameters and the increase of deformation parameters, while the non-continuum mechanics method thinks the rock mass as a discrete medium and the effects of cracking can be considered alone. Thus, the non-continuum mechanics is more suitable for the simulation of cracking in surrounding rock of roadways.
- North America > United States (0.28)
- Asia > China > Hubei Province (0.16)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.41)