ABSTRACT:

A very complex failure took place at an open-pit coal mine in the eastern Turkey. The floor of the open-pit heaved up as a result of the buckling failure of the coal seam and a combined form of shear and sliding failure of slope benches occured. The investigations showed that a weak clay band within the coal seam was the main cause of the failure. The friction angle of this band was less than 3° and dipped into the pit with an angle of 5 - 7°. The failure took place while the coal seam was uncovered. In this paper, the causes of the failure are investigated through some back analyses of failure modes on the basis of geotechnical investigations and limiting equilibrium techniques and the outcomes of these studies are presented and discussed.

RESUME:

Une rupture très complex est survenue dans une mine de charbon à ciel ouvert à I'est de la Turquie. Le plancher de la mine s'est souleve à la suite du flambage d'une veine de charbon. Les terrasses en pente se sont effondrees sous une forme combinee de cisaillement et de glissement. Les recherches ont indique que la cause principale de la rupture fut la presence d'une couche d'argile situee dans la veine du charbon. Cette couche ayant un angle de frottement inferieur à 3° etait inclinee de 5° à 7° vers la pente. La rupture s'est produit lors de l'excavation de cette couche. Dans cet article, les causes de la rupture ont ete examinees à partir de analyses a posteriori en considerant des modes de rupture et en utilisant les methodes de l'equilibre limite.

ZUSAMMENFASSUNG:

In einer offenen Grube einer Kohlenmine in der Osttuerkei fand ein komplizierter Bruch statt. Der Boden der offenen Grube hob sich auf Grund eines Knicken eines Kohlestreifens welcher mit einer Scherung und einer Abrutschung einer treppenartigen Böschung kombiniert war. Untersuchungen haben gezeigt, dass ein weiches Tonband die Hauptursache des Bruches war. Der Reinbungswinkel dieses Bandes betrug weniger als 3° und hatte einen Einfallswinkel von 5°-7°. Der Bruch ereignete sich als der Kohlestreifen unbedeckt war. In diesem Artikel werden die Haptursachen des Bruches anhand einiger Analysen der Bruchzustande auf der Basis geotechnischer Untersuchungen sowie der Gleichgewichtsbedingungen nachgeprueft; die Resultate dieser Studien werden anschliessend prasentiert und diskutiert.

1
INTRODUCTION

The failure of slopes during mining operations result in not only loss of the mining machinery but also human lives which makes the mining operations become very costly. Therefore, a good design is necessary before the initiation of mining operations since any change of design later on will result in high cost and time loss. A very complex failure took place at the Kişlaköy open-pit mine of Afşin-Elbistan Lignite Mining Complex in the Eastern Turkey in 1984. The pit-floor heaved up as a result of the buckling failure of the lignite seam and a combined form of shear and sliding failure of mining benches occurred. The investigations showed that weak clay layers existed in the lignite seam of about 20 m thick and one of these clay layers played an important role in the failure. The friction angle of this layer was about 3° and dipped into the pit with an angle of 6° (Ulusay et al, 1986). The failure took place in July 1, 1984 while the coal seam was uncovered by wheel-bucket type excavators. In this paper, the authors re-consider the 1984 failure from another point of view. The earlier back analyses carried out by the Tuerkiye Kömuer Işletmeleri Kurumu (TKI - Turkish Coal Enterprises) was based on circular or non-circular failure modes of mine benches. Examining the photographs of the failure, the heaved lignite seam shows a set of buckles.

This content is only available via PDF.
You can access this article if you purchase or spend a download.