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Collaborating Authors
The Influence of In-Situ Rock Mass Stress Conditions on Deformation and Load of Gateroad Supports in Hard Coal Mine
Lubosik, Zbigniew (Glówny Instytut Glrnictwa) | Waclawik, Petr (Institute of Geonics of the CAS, Institute of Clean Technologies) | Horak, Petr (OKD) | Wrana, Aleksander (Glówny Instytut Grnictwa)
Abstract The stress-strain state of the rock mass in the neighbourhood of the mining galleries is absolutely critical considering their behaviour particularly load and deformation. The stress-strain state can be affected by numerous geological and mining factors i.e. depth, mechanical parameters of the rock mass, the presence of faults, previous mining operations in case of multiple seam extraction and by the influence of the current longwall mining process. Considering this fact the advanced measurement plan was developed. The measurements were conducted in one longwall maingate of the Czech coal mines. The holistic investigation program consisted identification of initial rock mass stress tensor and monitoring of its changing during the approach of the longwall face. Two CCBO (modified overcoring) probes were installed to obtain pre-mining full stress tensor and afterwards three CCBM probes were installed to continuous monitoring stress state in rock mass ahead of advancing longwall. The triple height telltales and endoscopic methods were applied to monitor the behaviour of rockmass in close proximity of the gateroad. Hydraulic dynamometers and strain gauged rockbolts were used to determine the support load. Also the gateroad deformation observations were performed. The results of aforementioned measurements allowed to determine the potential relation between stress-strain rock mass state and behaviour of the investigated gateroad in coarse of longwall face approaching. 1. Introduction When applying a longwall extraction system in hard coal seams, it is essential to ensure that the gateroads are stable and of proper size during the whole mining process. In majority of European hard coal mining industry, there is a single gateroad system that prevails, consisting of steel arch yielding support. To ensure the proper maintenance of the roadway the mine managers have to efficiently cope with the rock mass movements of various intensity (e.g. roof sag, floor heave, and horizontal convergence) as a result of the extraction pressure impact [1].
Cable Bolt Bearing Capacity – An In Situ Parametric Study
Soucek, K. (Institute of Geonics AS CR, Institute of Clean Technologies) | Waclawik, P. (Institute of Geonics AS CR, Institute of Clean Technologies) | Konícek, P. (Institute of Geonics AS CR, Institute of Clean Technologies) | Ptácek, J. (Institute of Geonics AS CR, Institute of Clean Technologies) | Hastíková, A. (Institute of Geonics AS CR, Institute of Clean Technologies) | Kukutsch, R. (Institute of Geonics AS CR, Institute of Clean Technologies)
Abstract Cable bolts are used frequently as a secondary support system (with steel arch support) in difficult stress-strain conditions of deep coal mines. The load transfer mechanism of cable bolts depends on several factors, such as the strength, deformation and geometric properties of the bolts, resin and the surrounding rock mass so-called cable-resin-rock system (CRR system). The bonding length and bolt/borehole diameter ratio strongly influence the final bearing capacity of the CRR system. The study presents the behaviour of CRR system during a pull-out test which is usually used in the carboniferous rock mass in the Czech part of the Upper Silesian Coal Basin. A series of 28 pull out tests were performed on 3-m-long cable bolts, with various combinations of borehole diameters and bonding lengths, to understand this behaviour. Boreholes were drilled into a solid rock mass consisting of fine-grained sandstone to guarantee similar conditions during the pull-out tests. Video inspection and measurement of borehole diameters were performed to determine their quality and real diameters. Three characteristics were observed from pull-out test results: ultimate pull-out load; displacement of the end of bolt and system stiffness. Numerical modelling by FEM (Finite Element Method) was used to determine the stiffness of the CRR system for variable bolt/borehole ratios and bonding lengths each under constant load. A linear elasto-plastic model and a mohr-coulomb model were used for cable and resin-rock respectively. The results of the experiment may contribute significantly to improving of the methodology of cable bolts installation as well as the design of used cable bolts. Introduction The presented in situ experiment verifies the behaviour of cable bolts during pull out tests. These cable bolts are used in the conditions of carboniferous rock mass in the Czech part of the Upper Silesian Coal Basin. The cable bolts in this location are used primarily for the supplementary reinforcing of long wall roadways support. Their load transfer mechanism basically depends on bearing capacities and deformation characteristics of each component of the system, known as the cable-resin-rock (CRR) system (Aydan, 1989; Hutchinson & Mark, 1996). The study is divided into two parts. The first part presents the influence of bonding length on the resulting load-displacement curves of CRR systems and bond stiffness development. In this case, each borehole was drilled by drill bits having a diameter of 32 mm; the maximum recommended by the developer of the cables used. Following the bolt/borehole study is observed by practical measurements of borehole diameters which are statistically evaluated and presented in this study. The development of plastic points in the resin of variable bolt/borehole ratio and bond stiffness development for variable bonding length was of interest for numerical modelling.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.89)
Rock Bolting at the Room and Pillar Method at Great Depths
Waclawik, Petr (Institute of Geonics of the CAS, Institute of Clean Technologies) | Snuparek, Richard (Institute of Geonics of the CAS, Institute of Clean Technologies) | Kukutsch, Radovan (Institute of Geonics of the CAS, Institute of Clean Technologies)
Abstract A part of the coal reserves in the Karvina subbasin of the Upper Silesian Coal Basin is situated in protection pillars that lie under built-up areas. The longwall mining method is not suitable in these areas because significant deformation of the surface is not allowed. The room and pillar method with stable coal pillars has been proposed to minimise strata convergence. The method has been examined within the shaft protective pillar located in CSM-North Mine coal seam No. 30, where the mining depth ranged from 700 to 900 meters, being perhaps the deepest room and pillar panel in coal mining in the world [1–5]. As there is no relevant experience of using this method in the Upper Silesian Coal Basin, an extensive monitoring system has been implemented to enable the mining trial to continue safely. The monitoring is focused on the load-bearing capacity of the coal pillars and strata deformation changes induced by the room and pillar mining method. Precise monitoring was carried out in two adjacent coal pillars located within the row of pillars forming the panel. To monitor roof deformation, fourteen pairs of 5-level multipoint extensometers monitored roof displacements and eleven strain-gauged rockbolts were installed at various locations. Seven hydraulic dynamometer load cells measured the cable bolt loads were installed at the roadway intersections around the monitored pillars. The integral constituent of the extraction method (using driving machines like the Bolter Miner) is bolting as the sole support system of the roadways. The contribution deals with the behaviour of roof bolting, including the loading of the bolts, yielding of the rock mass and convergence in the roadways. The monitored parameters' database used to measure whether the room and pillar method is successful at this depth forms a necessary condition for verification of this method and its future application in conditions experienced in Upper Silesian Coal Basin.
ABSTRACT In terms of rock engineering and technology in hydropower construction, the slope stability and monitoring techniques for high slopes of Three Gorges Project, the stability and support technology for high slopes of hydropower projects in deep river valleys, the stabilization techniques for underground cavern group with large span and high side walls are introduced in this paper. As for rock engineering and technology in highway and railway construction, the Qinghai-Tibet Railway – new construction techniques in permafrost, the support techniques for large squeezing deformation in Wuqiaoling Tunnel, the construction techniques for tunnels in alpine and high-altitude region, the geological prediction techniques for tunnels in karst region, the microseismic monitoring and early warning techniques for rockbursts in deep and long tunnels are presented. For rock engineering and technology in mining engineering, the innovative techniques for roadway support in mines, the simultaneous extraction technique of pillarless coal and gas in coal seams with low permeability, the safe and efficient deep open mining technology, advances in monitoring, early warning and treatment of mine dynamic disasters are presented. In addition, the new anchorage techniques and precision blasting technique in rock engineering are introduced.
- Geology > Geological Subdiscipline (1.00)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.88)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.69)
- Materials > Metals & Mining (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Stress State Monitoring in the Surroundings of the Roadway Ahead of Longwall Mining
Waclawik, Petr (Institute of Geonics of the CAS, Institute of Clean Technologies) | Kukutsch, Radovan (Institute of Geonics of the CAS, Institute of Clean Technologies) | Konicek, Petr (Institute of Geonics of the CAS, Institute of Clean Technologies) | Ptacek, Jiri (Institute of Geonics of the CAS, Institute of Clean Technologies) | Kajzar, Vlastimil (Institute of Geonics of the CAS, Institute of Clean Technologies) | Nemcik, Jan (University of Wollongong) | Stas, Lubomir (Institute of Geonics of the CAS, Institute of Clean Technologies) | Soucek, Kamil (Institute of Geonics of the CAS, Institute of Clean Technologies) | Vavro, Martin (Institute of Geonics of the CAS, Institute of Clean Technologies)
Abstract Accurate knowledge of the stress-strain state of rock mass, not only in their vicinity but also in the wide surroundings of mine workings, is absolutely critical for precise support designing. Investigation of the rock stress is usually carried out by interpretation of the rock mass deformation processes, which can be relatively precisely observed and measured. In order to verify the stress state of the rock mass and changes in it induced by longwall mining, monitoring of changes in the rock mass stress in connection with the mine out of the longwall No. 371 202 was carried out. The seam extracted by monitored longwall has a thickness of approximately 2 m at a depth about 1100 m and lies within the Czech part of the Upper Silesian Coal Basin. Interpretation of the initial rock mass stress tensor and verification of its changes during longwall mining were the aims of this stress monitoring. A total of five probes were installed on the roof rocks of the main gate. Two compact conical-ended borehole overcoring probes were installed to obtain the pre-mining full stress tensor and afterwards three compact conical-ended borehole monitoring probes were installed to continuously monitor the stress state in the rock mass ahead of the advancing longwall. The monitored stress development contributes to our knowledge of stress distribution and its changes during excavation at great depth in multi-seam sedimentary deposits of the Upper Silesian Coal Basin. 1. Introduction Knowledge, which should be as accurate as possible, of the stress–strain state in rock mass is the determining factor for the proper planning of roadway supports [1]. That is why stress monitoring, primarily of the changes induced by longwall mining, is considered within this research project. The locality of longwall No. 371 202 in a mine of the Ostrava-Karvina Coalfields (Upper Silesian Coal Basin – USCB) was chosen for the research.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.92)