Rock mechanics investigations are carried out to evaluate the sublevel open stope mining method used at the tungsten mine in Bursa (Turkey) with respect to the stability of stopes, rib pillars and its various galleries. Although the orebody is massive in nature, it shows various rock mass strength characteristics. Major geological patterns and their strength characteristics are extensively studied together with the physical and mechanical properties of the ore-bearing rock (scarn) and the wall rocks. Using different rock mass classification systems, a careful evaluation of rock mass is established. Back analyses are carried out. The stability of stopes and pillars is studied. Design procedures and measures to be taken are suggested.
Des recherches en mecaniqe de roches ont ete faites pour evaluer la methode d'exploitation par chambres à sous etage employee a la mine de Wolfram à Bursa-Uluda, du point de vue de la stabilite des chantiers de travail, des piliers et des galeries. Bienque la formation soit massive, elle montre des resistances mecaniques differentes. Ses principaux aspects geologiques ainsi que ses resistances caracteristiques ont ete largement etudiees. De même les proprietes physiques et mecaniques de la roche contenant le minerai (skarn) et les roches formant le toit et le mur ont ete bien etudiees. En utilisant de differents systèmes de classification des roches massives, une evaluation soigneuse des roches a ete etablie. Une analyse ulterieure a ete effectuee. Des procedes pour la realisation du projet et les precautions à prendre ont ete suggeres.
Felsmechanische Untersuchungen werden durchgefuehrt, um den im Wolfram-Bergbau in Bursa (Tuerkei) angewandten Abbau mit Teilsohlenstrecken hinsichtlich der Stabilitat der Kammern, des Langfrontabbaupfeilers und der diversen Strecken auszuwerten. Obwohl das Erz in der Natur als massiver Körper auf tritt, zeigt das Gebirge verschiedene Festigkeitseigenschaften. Die geologischen Hauptformen und ihre Festigkeitseigenheiten sowie die physikalischen und mechanischen Eigenschaften des erzfuehrenden Gesteins (skarn) und des Nebengesteins wurden ausfuehrlich untersucht. Eine sorgfaltige Auswertung des Gebirges unter Verwendung verschiedener Gebirgsklassifizierungssysteme wurde unternommen und Rueckanalysen wurden durchgefuehrt. Die Stabilitat von Kammern und Pfeilern wurde untersucht. Entwurfsprozeduren und Sicherheitsmaßnahmen werden vorgeschlagen.
Uludağ tungsten deposits in Bursa, Turkey are located over 2100 meters near the peak of Uludağ Mountain and have been exploited by open pit and underground mining. Primary underground production comes from sublevel open stopes of full orebody height, which will subsequently be filled to aid pillar recovery (Fig.l). At present production from three primary sublevel open stopes is completed and at the fourth one it-is near to completion. The stopes and pillars between them are 15 meters in width. The height and length of the stopes are approximately 30 meters and 100 meters respectively. The first part of continuing rock mechanics research initiated at this mine concerns with the re-evaluation of the sublevel open stope mining method with respect to stability of stopes, rib pillars and its various galleries and drifts. Here, outcome of first part of this extensive rock mechanics investigations will be presented.
Uludağ tungsten mine is geologically situated in the scarn rocks between marbles of Paleozoic-aged Metamorphic Series and the younger granodioritic batholith. The Metamorphic Series which include amphibolites, gneisses and marbles at the base with mica-schists, phyllites and semi-marbles,at the top, and the overlying Permian-Carboniferous, limestones and clastic rocks,have been folded into a gigantic anticline during the Alpine orogeny accompanied by the intrusion of a batholith (Ketin 1947, P1nar-Lahn 1954, Ronner 1954, Kaaden 1958, Öztunall 1967). Continued tectonism and vertical uplift has subjected the Uludağ massif to intense weathering and erosion in Neogene and Recent times resulting in the exposure of granodiorite, marble and ore-bearing scarn in the vicinity of the summit region (Inan 1979). Tunsten bearing minerals are mainly found in scarn which is formed from marbles by the contact metamorphism of granodioritc intrusion. Two types of scarn have been recognized (Inan 1979):
Endoscarn is formed as a thin band within the magmatic mass of the contact zone and represents metasomatically altered granodiorite ("granitic scarn').
Exoscarn is formed within the marbles by contact metamorphism process and is generally dark green or reddish brown (garnet rich) in color with clinopyroxene, garnet, quartz, epidote and calcite as the main constituents. It also contains scheelite, wolframite, chlorite, tremolite, pyrite, chalcopyrite, fluorite, sphalerite, magnetite, hematite, molibdenite and bismuthite (Kaaden 1954). Marbles are white, coarsely crystalline, jointed tand contain relict bedding structures. These rocks are poor in ore and tungsten-bearing scheelite mineral is only present in thin vein formations. Granodiorite is a grey, medium-grained biotite-rich rock with plagioclase (40–45%), al- kali feldspar (1315%), quartz, biotite and muscovite as the main constituents.
Uludağ scarn belt is formed by the intrusion of granodioritic batholith into Palaeozoic metamorphic rocks and subsequent contact metamorphic of the marbles under the control of regional structural elements.
