The method of sublevel coal extraction requires multi caving of the hanging wall layers, which are recompressed, and where each represent a hanging wall in sublevel stoping. Extensive stress and deformation changes in the surrounding area and in the mine represent a safety hazard for employees since the supporting system in the mine roadway could collapse. By accepting geomechanical principals in following caving processes in underground coal mining with the Velenje mining method in above ground acquisition, there are mutual connections made, between the geomechanical parameters of the occurring geological materials in connection with the intensity of coal mining. A numerical model, which allows for in-depth analyses of the geomechanical processes which occur in the hanging wall, the footwall, and in the coal seam during sublevel coal excavation, is broadly applicable and highly relevant for analyzing the intensity and the level of caving processes in sublevel coal mining, and for making realistic plans for coal excavation with worker safety in mind.

The Velenje Colliery is operating in the largest coal deposit in Slovenia and at the same time in one of the thickest known coal seams in the world. The lignite seam is at one point up to 165 m thick. Until now more than 220 million tons of lignite coal were extracted from this seam. The colliery is situated in the so-called Velenje depression, which is a component part of the Southern Karawanke geotectonic unit. Considering the coal mining we can claim that rock bursts are a kind of constant that accompany the mining activities and represent occasional difficulties during production and at the same time disturb the local inhabitants. Based on complaints and at the same time because of the need for a thorough understanding of the causes of ground shaking, the Velenje Colliery decided for a systematic monitoring and evaluation of the seismic events. Based on these measurements the seismic events were precisely located and correlated to the technological process itself. Seismic events analysis indicates that these events are instantaneous stress relaxations piled up for a longer time because of the lignite extraction. This last statement can be confirmed by an analysis of the longitudinal seismic waving first arrivals (P) to seismological stations of the state monitoring network of Slovenia, Austria and Italy, even though such events are rare because of their weakness. The same analysis showed that the magnitudes rarely reach over 1.5 of local magnitude after Richter. Simultaneously with the seismic events analysis we analyzed the way of support relaxation. Tests on the existing support type K24 showed that this support is capable of withstanding large stresses without deformation. From these tests we found that the stress relaxation at currently used support type K24 can occur over relatively large deformations. The relatively simple stress-relaxation analysis at existing support shows it surprisingly well match to the energy relaxed at rock bursts in Velenje Colliery. Based on research done between 2003 in 2012 it is possible to conclude that the existing support type must be replaced with one that can relax the stress more frequently and with less deformation, consequently reducing rock bursts and increasing safety at work. Keywords: rock burst, steel arch, induced seismicity Premogovnik Velenje deluje na najve~jem nahajali{~u premoga v Sloveniji, ki je hkrati eno takih, ki ima najbolj debele plasti premoga na svetu. Plast lignita je na enem mestu debela tudi do 165 m. Do sedaj je bilo izkori{~enih 220 milijonov ton lignita iz te plasti. Premogovnik se nahaja v velenjski depresiji, ki je sestavni del geotektonskega dela Ju`nih Karavank. Pri rudarjenju premoga so hribinski udari konstanta, ki spremlja rudarske aktivnosti in ob~asno predstavlja te`ave pri proizvodnji ter isto~asno moti lokalno prebivalstvo. Zaradi prito`b in hkrati zaradi potrebe po razumevanju vzrokov tresenja tal, so se v Rudniku Velenje odlo~ili za sistemati~no registriranje in oceno seizmi~nh pojavov. Na osnovi teh meritev so bili seizmi~ni d...

This paper is based on the findings of empirical research conducted in 110 Slovenian companies. Using statistical methods, we examine the effect of the EFQM Excellence Model on the institutionalization of total quality management (TQM) tools and approaches, as well as financial results to motivate TQM implementation. Within the whole group of companies, special attention was paid to the results of applicants for the Slovenian Business Excellence Prize (SBEP), which were compared with other companies. The SBEP group showed better results compared with the other companies with regards to benchmarking, peer assessment, participation in quality and excellence awards, knowledge sharing, self-assessments and financial results. Dieser Artikel basiert auf den Ergebnissen einer empirischen Untersuchung in 110 Slowenischen Unternehmen. Durch die Anwendung statistischer Methoden untersuchten wir die Wirkung des EFQM Excellence Modells auf die Institutionalisierung der Total Quality Management (TQM)-Werkzeuge und Ansätze sowie finanzielle Ergebnisse, um eine Umsetzung des TQM zu motivieren. Innerhalb der gesamten Gruppe von Unternehmen wurde besonderes Augenmerk auf die Ergebnisse der Bewerber für den Slowenischen Business Exzellenz Preis (SBEP) gerichtet. Die SBEP Gruppe zeigte bessere Resultate bezüglich Benchmarking, Peer-Beurteilung, Teilnahme am Wettbewerb für die Qualität und Exzellenz Preise, Stimulation des Wissenstransfers, Selbstbewertung und finanziellen Ergebnissen.

The steel 31Mn4+QT630 is used frequently for mining support arches. The supports are cold strained, first during service, and again by re-rolling prior to reinstallation, which results in strain hardening and a loss of ductility. Consequently, many of the rerolled arch-segments are not suitable for reinstallation because their mechanical properties are inadequate. The objective of this work was to assess the feasibility of restoration of the required mechanical properties by means of a cost-efficient single step heat treatment. Specimens were cold deformed to different degrees in the range 0 % to 45 % to establish the relation between the degree of cold deformation and the hardness. Differently strain hardened specimens were subjected to subcritical annealing at temperatures 450 °C to 700 °C in the duration 0.5 h to 8 h to determine a suitable time-temperature combinations. Microstructures and mechanical properties were investigated of as-received, cold strained and recrystallized specimens. Tests performed were optical microscopy, scanning electron microscopy, tensile tests, hardness measurements and Charpy impact tests. Elongation at break of the as-received material was below the requirements of the applicable standard, and its microstructure contained significant fractions of pre-eutectoid ferrite and pearlite. Upon cold straining, hardness increased by approximately 2 HV per 1 % of strain. After one-hour recrystallization at 600 °C to 620 °C, the microstructure consisted of a ferritic matrix containing evenly dispersed globular carbide particles. The original ductility was restored, while the elongation, yield strength, and hardness were higher than in the as-received condition. These results confirmed that it is feasible to restore the original mechanical properties of heavily strained profiles with an adequate single-step heat treatment. Furthermore, they indicated that it should be possible to recover the required properties of inhomogeneously strained material with the same set of well optimized heat treatment parameters. Consequently, it should be possible to increase the reuse rate and to decrease the costs for new support arches significantly.

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. ACKNOWLEDGMENT As with any task of this magnitude, the results reported herein are the product of the efforts of many individuals from the Lynchburg Research Center and the Nuclear Power Generation Division (Fuel Engineering) who contributed in the areas of planning, operations, data reduction, and analyses. While space does not permit acknowledging all of the people involved, their assistance and efforts are greatly appreciated. The efforts of the following individuals who participated directly in the poolside examination are greatfully acknowledged: