1. High safety pillars stability control using EL beam displacement sensors in Lipica II quarryJože Kortnik, Sunny Nwaubani, Andrej Kos, 2014, original scientific article Abstract: In underground Lipica II. quarry for the excavation of natural stone, a modified room-and-pillar mining method is used, that is adjusted to the conditions of the site. In order to support and ensure the stability of underground chambers high safety pillars (HSP) are used. These pillars are made of surrounding stone and therefore intersected by discontinuities. The discontinuities represent high risk to the stability of underground facilities and workmen below/ itself. To ensure their safety the stress and strain parameters in height safety pillars are continuously monitored using two vibrating wire (WV) stressmeters inside the high safety pillars and two EL (Electronic level) beam sensors on the surface of the high safety pillar VS3. In the time period October 2010/June 2012 absolute max. measured deviation with EL beam sensors were D1=0.9 mm and D2=1.1 mm, which does not compromise the stability of the high safety pillar VS3. This paper presents the procedures of wedges deformation monitoring in safety pillars with EL beam sensors in the Lipica II underground natural stone quarry.
Keywords: beam sensor, high saftey pillar, monitoring, natural stone, room and pillar mining method
Published in DKUM: 14.06.2018; Views: 1004; Downloads: 78
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2. An analysis of the geomechanical processes in coal mining using the Velenje mining methodGregor Jeromel, Milan Medved, Jakob Likar, 2010, original scientific article Abstract: With in-depth geomechanical analyses of sub-level mining using the longwall mining method we can identify the relationships between the physical and mechanical parameters of geological materials, depending on the intensity of the coal extraction. The extent and the intensity of the mining operations impose impacts on the stresses and cause deformation changes in the rocks and in the coal seams on a broader area of excavations. The method of sub-level coal extraction requires multi-caving of the hanging-wall layers, which are recompressed, and in sub-level stoping each represents a hanging wall. The repeating processes of caving-in and compression, from the aspect of the theory of plasticity, have been relatively little researched because every such process brings about structural changes in natural, multi-caved and recompressed materials in the hanging wall. The intensity of the coal extraction has direct impacts on the surrounding and distant mining areas. Extensive stress and deformation changes in the surrounding area, and in the mine, represent a safety hazard for the employees, since the supporting system in the mine roadway could collapse. Therefore, a controlled excavation of the coal, and a good understanding of the geomechanical properties of all the materials and processes involved, is extremely important for planning and managing economic production, while also ensuring safe mining operations.
A numerical model that allows for in-depth analyses of the geomechanical processes that occur in the hanging wall, the footwall and in the coal seam during sub-level coal excavation, is broadly applicable and highly relevant for analysing the intensity and the level of the caving processes in sub-level coal mining, and for making realistic plans for coal excavation with workers’ safety in mind.
Keywords: coal mining, sub-level mining method, longwall coal mining method, carving processes, finite-difference method, FLAC, mathematical model
Published in DKUM: 11.06.2018; Views: 1117; Downloads: 96
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3. Optimization of the high safety pillars for the underground excavation of natural stone blocksJože Kortnik, 2009, original scientific article Abstract: For the first time in Slovenia, the underground excavation of natural stone blocks was introduced on a trial basis at the Hotavlje I colourful limestone quarry in 1993, and in 2002 also at the Lipica II quarry. This was primarily because of the geological structure of the site, the quarry’s condition, the potentially large amounts of the overburden in the event of an expansion of the surface part of the quarry, and the increasing needs for this raw material, i.e., natural stone. Underground The underground excavation of natural stone blocks is done using a modified room-and-pillar excavation method that is adjusted to each site’s characteristics, with regularly or irregularly distributed high safety pillars. Since the underground excavation of natural stone blocks is performed at a relatively shallow level under the surface, i.e., at a depth of only 10-40 m, the value of the primary vertical stress state is also relatively low (<1.0 MPa). This significantly increases the risk of wedge-shaped pieces or blocks falling out of the ceiling in open, underground spaces. In previous years, special attention was paid to the installation of stress-strain systems for controlling the planned dimensions (width and height) of large, open, underground spaces (rooms) and the dimensions of the high safety pillars, along with continual monitoring and identification of the instability phenomena in the ceiling and sides of the large open spaces (rooms). The paper presents the procedures for the planning, optimization and monitoring of high safety pillars for the underground excavation of natural stone blocks.
Keywords: natural stone, high safety pillars, room-and-pillar mining method, underground mining, quarry
Published in DKUM: 06.06.2018; Views: 1011; Downloads: 142
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