Introduction to longwall mining and subsidence essay

Frost Since Appalachia lacks definite physiographical or topographical boundaries, there has been some disagreement over what exactly the region encompasses.

Introduction to longwall mining and subsidence essay

In underground coal mining engineering, one of the most important tasks is to monitor, predict and manage the surface subsidence due to underground coal excavation. The impact of underground mining excavation reflects as subsidence of the overlying strata and the formation of surface depressions soon after excavation.

Introduction to longwall mining and subsidence essay

The surface subsidence is one of many natural processes that exhibit a progression from small beginnings that accelerate and approach a climax over time. When detailed data is lacking, a logistic function is often used.

Furthermore, the time estimation of the next and the final epoch measurement is considered. The thickness of the coal deposit ranges from 20 to m.

The coal layer is m thick at a depth of m, and the greatest amount of coal can be found at a depth of m [ 1 ]. The VMM is characterized by continuous caving-in of the hanging wall layers, where the length of longwalls amounts from 80 to m and the length of panels vary from to m Figure 1.

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Underground coal mining excavation leads to subsidence of the overlying strata and the formation of surface depressions. In underground coal mining engineering, some of the important tasks are to monitor, predict and manage the surface subsidence due to underground coal excavation.

Since more excavation panels are active at the same time and the excavation of one begins right after the excavation of another ends, it is hard to talk about the impact of one particular excavation panel to the surface.

Measurements for determining the movements of the ground include geodetic measurements of planar and height networks. The subsidence at the surface does not occur suddenly, but develops progressively as the coal is extracted within the area of influence of the extracted coal panel.

Furthermore, five observation points, whose analysis results are presented in this paper in more detail, are shown. Materials and Methods 2. The depression is meshed with local faults from different ages and runs in different directions.

River and lake alluvia consisting of sand and clay, whose thickness totals m at the most, represent the hanging wall of the seam Figure 3. Immediately above the coal seam there are clay layers ranging from a few hundred meters to minimum of six meters.

The footwall of the seam consists of clay and marl lying on triassic limestone and dolomites [ 3 ]. The coal deposit is lens-shaped, 8.

The deposit is closest to the surface at the edges and deepest in the middle. From a geomechanical point of view, the strength and rigidity of the lignite layer is much higher than the materials in the hanging wall and in the footwall of the deposit.

This fact is important, both for planning excavations as well as for designing the most suitable excavation method, which needs to be adapted to the natural geological and geomechanical conditions [ 2 ]. Also, the caving-in of the materials in the adjacent hanging wall is different from the subsiding hanging-wall layers lying above, where clay and silt layers are first plastically reshaped, while the layers situated higher up are bent and subsided to the surface, where large depression lakes have been formed as a consequence of the mining activities.

Longwall Mining Overview | Introduction | underground COAL

Mining Method Underground lignite mining in Velenje has a rich history and tradition. Industrial lignite mining from the Velenje deposit has taken place for more than years and is ongoing at a level of around 3.

Since the start of mining, approximately million tonnes of lignite have already being mined.Feb 20,  · After the mining company cut off water and electricity during the lengthy miners strike, residents marched on the pumping station at Waterford Lake, demanding the utilities be restored and, during a confrontation with armed company police, shots were fired and Davis was killed.

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Mine Subsidence Engineering Consultants ii August CONTENTS DOCUMENT REGISTER i CONTENTS ii LIST OF FIGURES ii CHAPTER 1. INTRODUCTION TO LONGWALL MINING AND SUBSIDENCE 3.

Longwall mining is a more advanced method that increases the chances of subsidence beyond that of the original "room-and-pillar" approach, in which corridors are mined through a seam and the unmined area creates pillars that support the mine roof and other rock strata above.

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