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1.
High safety pillars stability control using EL beam displacement sensors in Lipica II quarry
Jože Kortnik, Sunny Nwaubani, Andrej Kos, 2014, izvirni znanstveni članek

Opis: 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.
Ključne besede: beam sensor, high saftey pillar, monitoring, natural stone, room and pillar mining method
Objavljeno: 14.06.2018; Ogledov: 360; Prenosov: 30
.pdf Celotno besedilo (491,51 KB)
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2.
Optimization of the high safety pillars for the underground excavation of natural stone blocks
Jože Kortnik, 2009, izvirni znanstveni članek

Opis: 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.
Ključne besede: natural stone, high safety pillars, room-and-pillar mining method, underground mining, quarry
Objavljeno: 06.06.2018; Ogledov: 390; Prenosov: 76
.pdf Celotno besedilo (557,08 KB)
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3.
Non-linear finite-element modelling of room and pillar mine workings including the strain-softening behaviour of the rock mass
Salim Bensehamdi, Abdelbaki Seriani, 2008, izvirni znanstveni članek

Opis: A two-dimensional model adopting post-failure criteria was used to simulate the behaviour of the rock mass and the development of yield zones around room and pillar mine workings. The model conformed to the strain-softening behaviour of the rock mass and accounted for its post-failure residual strength. The structural-stability-analysis approach accounted for the main features of the mine structures’ yield produced during loading through changes in the rock material’s stiffness and the subsequent evolution of the stresses. A comprehensive parametric analysis was performed and the inevitable effect of the interaction of the roof, pillar and floor on the overall stability limit of the mine was investigated. The numerical results clearly showed that the finite-element linear models could not realistically represent the true behaviour of the mine structure. However, they clearly demonstrated the limitations of the finite-element linear solutions in representing the true behaviour of the mine structure, particularly when the rock-mass structure is relatively weak, and that a non-linear approach was justified.
Ključne besede: non-linear FE analysis, yielding, plastic zones, room and pillar mining, residual strength, stability assessment
Objavljeno: 05.06.2018; Ogledov: 403; Prenosov: 41
.pdf Celotno besedilo (651,93 KB)
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