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Abstract: The topic of underground excavation in weak rock mass for civil applications is well analyzed and studied by researchers and engineers. However, limited studies are available for weak ground conditions in underground mining environments. Most rock engineering and rock mass classification systems were developed based on tunneling and civil applications of rock, soil mechanics and case histories. The current challenges faced by many underground mine operators working on excavations in poor ground are to ensure a safe working environment, maintain stability of the underground infrastructure, preserve mineable reserves, and to perform this economically. This paper provides a summary and perspectives on the application of commonly used ground support systems updated with information on Thin Spray on Liners to address weak rock mass conditions for underground mines based on a practical engineering approach. INTRODUCTION The increase in rock mechanics understanding, evolution in ground support systems and computing technology when integrated with practical experience enables engineers to design safer underground excavations in weak rock mass. The focus of this paper is to promote discussion on the practical aspects of the utilization of modern rock support types in underground metalliferous mines to address weak rock mass conditions. This paper is an updated version of the authors' earlier publications with the introduction to Thin Spray on Liners which is currently gaining the attention of mining operators (Foo et. al, 2010). The objectives of rock mechanics are to ensure the overall stability of the mine structure and safety of the working area, and preserve the condition of ore reserve for mining (Brady and Brown, 1993). Rock support and reinforcement systems are not the only elements enabling underground excavations to meet these objectives. Rock supports are commonly installed in stages within an excavation to achieve controlled ground displacement equilibrium.
- North America > United States (1.00)
- South America (0.93)
- Asia > Middle East > Turkey (0.28)
- (2 more...)
Abstract: Ever increasing depth of mineral extraction presents a challenging environment for hard rock underground mines. High in-situ stresses and associated seismicity with potential rockburst hazards are the major decisive factors contributing to the choice of a ground support regime. Conventional ground support systems, designed primarily for static loads, are not always capable of providing safe working conditions for underground personnel in seismically active mines. Systems specifically developed to resist dynamic loading and allowing for larger deformations are therefore preferred alternatives. High-tensile chain-link mesh has a proven record of successful use in open cut operations in various rockfall barrier installations due to its high energy absorption capacity. It has also been used in underground operations in various parts of the world. This paper describes a method of mechanized installation of a chain-link mesh as trialed at the moment in Kiruna mine in Sweden as well as has been installed in South Africa, Australia and Switzerland. 1 INTRODUCTION Increasing stresses and associated seismicity with the risk of rockbursts is a serious challenge for deep hard rock underground mines. Conventional ground support systems are not effective in rockburst conditions and thus have to be replaced by systems specifically designed for dynamic loading and large deformations. One of the used ground support products in rockbursting conditions is high-tensile chain-link mesh. Due to its strength and flexibility, the mesh was able to absorb the kinetic energy thereby slowing down the impacting rock masses. The high strength of the mesh is required to transfer the rockburst loads to the anchors and to avoid puncturing of the mesh by the rock fragments. Although its ability to withstand large rock mass deformations has been proven, its use in mines is limited due to the high labour intensity.
- Oceania > Australia (0.52)
- Europe > Switzerland (0.51)
- Europe > Sweden (0.35)
- Africa > South Africa (0.35)
Towards Proving the Feasibility of a New, Composite Polymer Liner
Swan, G. (CAMIRO/Deep Mining Research Consortium) | Spencer, E. J. (CAMIRO/Deep Mining Research Consortium) | Graham, C. (CAMIRO/Deep Mining Research Consortium) | Hastings, D. (3M Canada) | Rayner, T. J. (3M Canada) | Livingstone, D. (3M Canada) | McDonald, N. W. (ABB Canada) | Bond, B. (ABB Canada)
Abstract: Thin Spray-On Liners (TSLs) have been the subject of much international research, laboratory testing and underground trials over the past 20 years and yet their fully functional and widely justifiable application in mining has yet to be achieved. While the explanation for this is partly technical, it is also clear that proving and communicating the operational and economic case for why a mine should change from mesh or shotcrete liners to a TSL is not a trivial matter. Evidence must be presented and communicated effectively, that is both obvious and compelling for a mine operator. The paper describes recent work carried out and directed towards this end, with funding from CAMIRO's Deep Mining Research Consortium and additional support from 3M Canada and ABB Canada. Future plans are also presented to demonstrate the performance of a new 3M composite TSL/yielding bolt support system in underground trials where the substrate rock is intended to fail through a number of mining-induced mechanisms. 1 INTRODUCTION Underground rock support typically comprises two or more basic components: a sur-face liner of screen or shotcrete, together with various configurations of rockbolts working with the surface liner. Shotcrete in mining has evolved over the last 25 years to become a mainstay liner component, but is challenged by its brittle nature and lack of yielding capacity in seismically active and/or strongly deforming ground, as well as by material handling issues. This statement alone may be seen as the original motiva-tion for seeking a tough or yielding alternative to shotcrete in the form of a thin spray-on (deformable) liner, or TSL. Here "thin" implies that it would have an order of magnitude less material volume and thus a significant reduction in material handling issues compared to shotcrete, particularly in the context of deep mining.
Abstract: Abrasive water jet (AWJ) cutting is a green machining and processing technology that has found extensive applications for a long time because of its being cold, damage free and sensitive cutting technique. The purpose of this study is to optimize the operational parameters including traverse velocity and pump pressure with reference to cutting efficiency parameter, namely depth of cut, in the cutting operation using abrasive water jet on a real marble commercially named as Usak Green and a granite sample commercially named as Beypazarı Granite and also to develop cuttability charts in abrasive water jet cutting for these samples. The main goal in this study is to maximize the depth of cut and also find the operational parameters that would allow us to reach this goal. For this purpose cuttings were performed with abrasive water jet cutting machine at six different traverse velocities (400, 600, 800, 1000, 1500, 2000 mm/min) and six different pump pressures (90, 120, 180, 230, 300, 360 MPa) with constant standoff distance (5 mm), abrasive flow rate (225 g/min) and nozzle diameter (0.3 mm) based on the factorial design of the experiment by using Design Expert 7.0 and determination of the depth of cut after each cutting operations. As a results of this study cuttability charts indicating the optimum working point with respect to the depth of cut for a real marble and a granite sample were developed for cutting with abrasive water and presented in this study. These charts could be of help in the natural stone industry in terms of a more efficient usage of the abrasive water jet cutting machine. By using them, it is easy to determine the depth of cut in different operational parameters before starting the cutting operation.
- Asia (1.00)
- North America > United States > Colorado (0.28)
- Research Report > New Finding (1.00)
- Research Report > Experimental Study (1.00)
- Geology > Rock Type > Igneous Rock > Granite (0.71)
- Geology > Geological Subdiscipline > Geomechanics (0.69)
- Materials > Metals & Mining (0.94)
- Energy > Oil & Gas > Upstream (0.46)
Abstract: The size of rock blocks play an important role in mining applications (stability, excavation, etc.) and in-situ block size distribution has been the best way to assess block sizes in rock masses. In addition, the assessing of several size-reducing applications (excavation, blasting) is carried out using interpretations of broken block size distribution. There are several methods that attempt to predict the size of in-situ or broken blocks and their corresponding distributions. The most common kinds are based on direct measurements of free surfaces and piles. These methods have long been used successfully in many mining operations. Due to a lack of proper consideration, economical losses occur during the planning of dimensional stone quarry operation. This study aims to assess the final excavation of useful (marketable) rock blocks in the present dimension quarry and/or the pre-evaluation of potential resources. The size distribution curves have been carried out as assessment tools for this aim. The basis of the developed approach is to compare in-situ, useful and non-useful dimensional blocks. Thus, it has been attempted to create a new economical perspective in dimensional quarry sectors. Sieve curves have been used as principle assessing tools. To show the effect of methods in the study, a field study is implemented and the results of the study are also given in the paper. 1 INTRODUCTION The economic potential of any block quarry is dependent on the recovery rate, defined as the total volume of useful rough blocks extractable from a fixed rock volume, in relation to the total volume of the moved material. The natural fractural system, the rock type(s) and the extraction method used directly influence the recovery rate. This situation is also strongly valid in the quarrying process, especially in the extraction of blocks from a main deposit.
- Research Report > New Finding (0.50)
- Overview > Innovation (0.40)
- Geology > Geological Subdiscipline > Geomechanics (0.48)
- Geology > Rock Type (0.34)
Abstract: Mapping the orientation of structural discontinuities in a drill and blast tunnel, along a natural slope face, or a blasted rock cut requires time, various instruments, recording material, and subjects the engineer to the hazard of unstable blocks. Mapping discontinuity information from lidar data is an excellent alternative that pro-vides the engineer with time saving measures in the field, and a large degree of flexibility while processing the digital data. However, the time between data collection and evaluation of joint sets through digitization of their surfaces can be lengthy. Innovative research at NGI is been conducted to enable the automatic production of stereonets based on a lidar generated mesh. The software, PlaneDetect, relies on three subroutines of smoothing, masking, and identifying rock discontinuities. The result of the processing in PlaneDetect is the original inputted 3D polygonal model with all fractures digitized and colored by orientation. As well, a text file is created with information regarding characteristic of each identified surface. Thorough testing is being conducted on lidar data generated by high-speed phase based scanners as well as long range time of flight scanner. The results demonstrated so far are highly accurate in comparison to manual digitizing, reliable, repeatable, and extremely fast. The algorithm theory and two examples are presented herein. INTRODUCTION Geological mapping typically involves a lengthy evaluation of rock discontinuities, their orientation, and surface characteristics. Measurements made in the field are typically done so with a compass and an inclinometer. These evaluations occur in open pit and underground mines, along transportation corridors, in tunnels and mountainous regions prone to rockfall. Although state-of-practice, field evaluations typically put the engineer in the direct path of the potential hazard, as shown in Figure 1, in an investigation along a rail line and at a bench face in an open pit mine.
- Europe (0.95)
- North America > United States (0.47)
- Energy > Oil & Gas > Upstream (0.67)
- Materials > Metals & Mining (0.55)
- Transportation > Infrastructure & Services (0.54)
- Transportation > Ground (0.54)
Abstract: This paper introduces the use of 3D Light Detection and Ranging (LiDAR) for measuring rock mass discontinuities and tunnel excavation profile details, based on a case study of the Raabstollen tunnel in eastern Styria, Austria. The basic survey procedure involves: creating a comprehensive 3D LiDAR point cloud model (PCM); forming detailed triangulated surface model (TSM) from the PCM; and mapping of fracture network characteristics (discontinuity orientation, size, intersection and termination) using advanced digital processing techniques. The result is an actual discrete fracture network being mapped directly on the excavation surface, which facilitates evaluation of over- and underbreaks and provides a permanent digital archive for further analysis and evaluation. This case study shows that LiDAR surveys can provide high quality data for both geological documentation (especially rock mass structure) and excavation geometry. 1 INTRODUCTION Geo-spatial data representations of rock mass conditions encountered during tunnel construction are becoming increasingly common, as they have been found to facilitate technical and economical project success. However, the immediate installation of ground support at the working face gives the engineering geologist/ tunnel engineer limited opportunity to inspect and document the ground conditions, and rock mass conditions exposed in the crown area are often not directly accessible for close inspection and measurements. The increased application of remote characterization methods has greatly enhanced tunneling documentation. Over the last 10 years, digital photogrammetry soft-ware has evolved into useful mapping tools for underground excavation (e.g. Gaich et al 1998, 2005, Birch 2008). More recently, terrestrial Light Detection and Ranging (LiDAR), also referred to as 3D terrestrial laser scanning (TLS), has seen increased application in rock mass characterization studies (e.g., Kemeny & Turner 2008, Ferre-ro et al 2009, Lato 2010, Sturzenegger 2010, Liu & Kieffer 2011).
- North America (0.95)
- Europe > Austria > Styria (0.35)
Abstract: Current documentation in underground excavation involves coarse measurements of the tunnel profile before and after support installation, in combination with hand-written notes and assessment by a geologist or engineer on the rock mass quality. Laser scanning offers a fast, efficient documentation system of both the rock and the support that can be archived indefinitely. Theoretical applications are vast and include comparison of as-built to design specifications, verification of support installations, measurement of liner thickness and bolt spacing, and documentation of rock mass properties including orientation of fractures and zones of weakness. LiDAR in underground constructions had a commercial christening in the first half of 2011 and has been used as a design tool during the construction of a water storage cavern in Norway. The storage cavern has been built in relation to an existing water treatment plant and a pedestrian escape route connects the cavern to the plant. Two zones of bad rock conditions were unveiled during construction, each of approximately 15 m length. Permanent rock support in these zones consisted of rein-forced ribs of sprayed concrete (RRS) in addition to sprayed concrete and bolts as temporary support. The initial cavern design had underestimated the need for heavy rock support and there was therefore limited space for the extra support. The LiDAR data has proved to be a priceless tool in assessing the exact placing of the RRS in order to minimize the effect on the original design, to document the exact thickness of sprayed concrete for temporary support in the same areas, and in the redesign of the pedestrian escape route. 1 INTRODUCTION In 2010 NGI was commissioned by Nedre Romerike Vannverk (NRV), Norway, to document the excavation of a new cavern for water storage on a daily basis.
- Water & Waste Management > Water Management > Lifecycle > Storage/Transfer (0.81)
- Water & Waste Management > Water Management > Lifecycle > Treatment (0.55)
Abstract: 3D terrestrial laser scanning (TLS) techniques have developed for more than ten years and are now becoming more popular for 3D surveying, documentation, design and other applications. There are different types of scanning techniques, e.g. pulse-based, phase-based and triangulation-based scanning techniques. Comparing to these techniques, the phase-based technique shows some advantages for underground construction. In this paper, the comparison between different types of scanning tech-niques is presented. The most advantages for a phase-based scanner are: Higher scanning speed than others, so one can quickly perform field scanning with few minutes for each scan; High resolution of up to 0.5 mm resolution; Capture grey-scaled laser image in the dark and with large coverage (rotating 360 degrees both hori-zontal and vertical; Scanning range is up to more than 100 meters, which is enough to almost all the underground construction projects. Some application examples are presented to show the advantages by using the phase-based scanner in the under-ground construction. There are different applications in a whole procedure of the un-derground construction project, e.g. blasting for the new tunnel, operation and mainte-nance for the existing tunnel. The phase-based scanning techniques can provide more information for quality control of the geometry of the blasted tunnel (over and under break), thickness of the sprayed concrete, for documentation of rock types and water leakage with the laser images, for 3D surveying (both cross-section and 3D mesh-model with high resolution), for 3D fracture mapping, and is also useful to obtain the relational information of the in-situ condition in the field. INTRODUCTION 3D terrestrial laser scanning techniques have been developed since the late of 1990's, and are now becoming more popular for 3D surveying, documentation, design and other applications. There are several different types of laser scanners in the market, which have their specifications.
Abstract: 3D imaging has become a frequently used method for gathering quantitative rock mass data and documenting in situ rock mass conditions after excavation. As a supplement to conventional geological mapping it increases working safety and improves data completeness. The method is fast and easy to apply, and provides a permanent, objective, accurate, and detailed 3D record of the rock mass. Apart from the documentation, the results of a 3D image analysis form a part of the final support design and allow for the prediction of the rock mass conditions. This paper briefly reviews the 3D imaging technology following the computer vision principle and subsequently the additional possibilities for the registration of 3D images without the need for any external surveying system. After describing the capabilities for geological mapping a recent extension of the technology is given where instant geological mapping on digital photographs right in front of a tunnel face is performed and measurements are upgraded to 3D information. 1 INTRODUCTION Photogrammetry is the art and science to measure from photographs with first applications in topographic mapping dating back to 1849 (Slama 1980). Classical photogrammetry required purpose made (and hence expensive) cameras as well as mechanical complex equipment in order to assess the photographs especially if accurate measurements were sought. Digital imagery opened the door to algorithmic processing and led to new concepts often summarised under the term "Computer Vision" (Faugeras 1993). With its help off-the-shelf cameras have been applied and algorithms better suitable for computer programs have been adopted (Gaich et al. 2008). Since geological mapping involves the use of visual data (e.g. rock type or rock quality) and geometric data (e.g. spatial orientation or spacing), it is straightforward to use an entity such as a 3D image for geological assessments.
- Europe (1.00)
- North America > United States (0.68)
- Geology > Geological Subdiscipline > Geomechanics (0.49)
- Geology > Rock Type (0.48)