Mining Methods And Risks Evaluation: A Guide

Parameter Save Time On Research and Writing Hire a Pro to Write You a 100% Plagiarism-Free Paper. Get My Paper	Discussion
Mining Methods	Long wall is a type of large scale mechanized mining method. It involves mining seams of coal in slices. There are three longwall mining methods: the Single Pass Longwall mining method (SPL), Multi-Slice Longwall mining method (MSL) and Longwall Top Coal Caving mining method (LTCC) (Riaza and Gupta, 2015). Each is used depending on the topography of the area and the thickness of the coal being mined. The single pass method is used when the seams are less than six meters in thickness. The seam of coal is divided into slices of predetermined length and extracted by the workers using equipment suited for the operation. The Multi Slice Longwall applied when seams of coal are more than six meters in thickness. The mining is then done in horizontal slices. Economically speaking, the investment costs are twice higher for Multi Slice Longwall method as compared to Longwall top coal caving method. Compared to the Multi Slice Longwall method, the Longwall Top Coal Caving method is more effective as it is more economical as it requires less labour and equipment and can be applied to thicker seams more easily (He et al., 2013). Developed by the French in their coal mining industry, the longwall top coal caving method has one face of the seam operated on the base while the coal that is left on top is taken from the window through the roof support.
Pillar Sizes Save Time On Research and Writing Hire a Pro to Write You a 100% Plagiarism-Free Paper. Get My Paper	The size of the pillar, according to Woodruff (2016) depends on the strength of the coal seams, the nature of the roof and the hardness floor of the mine, the effect of the gases available in the atmosphere and how long the pillars will have to support the coal seam, otherwise known as the time dependent strain. When the coal is strong, the mining operation will require pillars with lesser width. The pillar edges will be affected by the strength of the roof; if the roof is strong, the edges will be crushed. The strain on the pillars increases with the passage of time while the load carried remains constant. Thus if the pillar is not sufficient in size, it may fail despite being stable in the early stages. Camp asserts that pillars are important for the safety of the workers in the mines thus the main purpose of the pillars that are placed at the head gate entry and the tail end entry is supporting the overlying strata (2016). The head gate is used for transporting the miners, coal and the supplies while the tail entry is used for ventilating the mine from dust. According to Bise, the size of the pillars to be used depends on the thickness of the seams, the equipment being used and the depth at which the mining is to be done (2013). When the pillar is too thick, there are losses made since the coal at the pillar is not mined. Though there is a possibility to mine the coal at the pillar as the mining advances, there is still coal loss by a marginal percentage when retreat mining is applied. When the pillar is too thin, there is the possibility that the coal roof will collapse into the mining area (Absalov, 2016). The collapse will lead to workers being harmed, slowing down the process due to disruption of normal flow of work, and a loss of a percentage of the coal that was to be mined due to disturbance to the strata and the mix-up with dust and other undesirable elements. A typical pillar measures six to forty five meters in width and six to twelve meters in length. The exact size is determined y the mining conditions of the area. To aid the support of the pillars, additional support is provided by roof bolting (Singhal, 2014).
Choice of a Panel Width When Mining .	The panel width when mining is important during the development stages. It also determines the technical economic indices of the scope and the productivity of the production unit according to (Bondarenko, Kovalevs’ka, & Ganushevych (2014). It determines the placements of the head and tail entries. Setting up the required machines and workflow depends on the size of the panel and could take averagely nine to twelve months. The size also determines the amount of coal that is going to be extracted in addition to the type of equipment that will be used. The perimeter cut out for the panel should allow for the continuous operation of the mine using the equipment in use. Usually, the equipment in use is self-advancing hydraulic roof supports, an armored conveyor belt parallel to the coal wall face to transport the coal as soon as it mined to the designated area and the coal shearing machine that allows for the coal to be sheared and placed on the conveyor belt. Normally, if the quality of the mine is favorable, up to 80% of the coal being mined will be recovered(Wain, 2014). Around the panel, there should be 10 to 15 feet space left to allow for sufficient room for the miners to work in addition to the equipment.
Best sequence of mining for a longwall operation to extract coal efficiently.	There are two ways of mining coal efficiently: the retreat and advance longwall methods (Richards, & Szwilski, 2012). When the coal is less than 6 meters deep the best method is to use the single slice longwall method. While if the coal mine is going to be more than 6 meters, the economics safety and reliability of the method should be considered (Kesler & Simon, 2015). For instance if the mining depth is 20m, the multi slice method can be used 5 times for seam thicknesses of 4 m or the longwall top coal caving method can be used to extract a layer at the bottom of say 4m and the rest can be allowed to cave in in order to allow for the recovery of the coal seam that collapses. Of the two, the longwall top coal method is best as it reduces the cost of the operation. The amount of coal lost in the rubble during the collapse is negligible and can be negated by the benefits accrued as compared to the resources that would have been spent excavating the 4 layers using the multi slice method. The procedure used during the mining process is process is either retreat or advance. For the retreat method, the entries are used to block the longwall panel and once this is done, the extraction of the coal from the seams begins from the end of the panel and advances towards the front and main entry of the coal mine (Singh, P. et al., 2017). In the advance system, however, the mining begins at the main entrance and moves towards the end of the panel. As the coal is removed, hydraulic systems and control systems are activated to help the conveyor move forward and transport the coal to the designated location. Continuous development on both entries on each side that is practically dead work is disadvantageous in the advance long wall method. This is in order to ensure that the entries are both open due to the gob formed when the caves collapse (Li, 2016). The ventilation of the mine is also hectic while using the advance longwall method. The retreat method is preferred as it extracts coal from the seams and the ventilation work is much less and there is no need for extra dead work during the process.

Simpsons rule is as follows:

The following parameters were used in the first calculation

Pit Pillar (100 m)
Seam thickness (3.6 m)
Main gate development dimensions
- 4 headings (3.6 m x 4.5 m)
- 3 pillars (8.0 m wide)
Main gate pillar width (50 m)
Head and Tail gate development dimensions
- 2 headings (3.6 m x 4.5 m)

1 pillar (8.0 m wide)

x	f(x)	h/3	area	volume	f(x)ii	h/3	area	volume
0	3050	400			2900	400
1200	3000	400			3050	400
2400	3050	400	7240000	26064000	2800	400	7160000	25776000
3600	2950	400		0	2600	400		0
4800	2950	400	7120000	25632000	1500	400	5880000	21168000
6000	2950	400		0	1350	400		0
7200	2600	400	6940000	24984000	700	400	3040000	10944000
			21300000	76680000			16080000	57888000

		Total	Volume	134568000

VOLUME OF SEAM COAL USING PANEL LENGTH AS 1400M
2300	2900	3.6	24012000
2300	3000	3.6	24840000
2300	2800	3.6	23184000
2300	3000	3.6	24840000
2300	2700	3.6	22356000
2300	1500	3.6	12420000
		total	131652000

x	f(x)	h/3	area	volume	f(x)ii	h/3	area	volume
0	3000	600			2700	600
1800	3050	600			3050	600
3600	2700	600	10740000	38664000	2850	600	10650000	38340000
5400	2800	600			1900	600
7200	2600	600	9900000	35640000	700	600	6690000	24084000
			20640000	74304000			17340000	62424000
		total	volume	136728000

Thus the % of coal that is recovered is
length of panel	volume (simpsons)	volume (panels)	pillar volume	volume remaining	% of coal recovered
1150	134568000	126891000	45691.2	7677000	6%
2300	136728000	131652000	45691.2	5076000	4%

The analysis then of the above calculations is that when the panels are larger, more coal is mined from the seams and thus the amount recovered (i.e. that remains) is much less, at 4% while with panels of lesser width, more coal remains thus the amount recovered is 6%. The pillar sizes also change according to the panel width due to the load they carry. Panels with lesser width require panels that have lesser dimensions.

References

Abzalov, M., 2016. Applied Mining Geology, Springer.

Bise, C.J., 2013. Modern American Coal Mining: Methods and Applications, Society for Mining, Metallurgy and Exploration Incorporated.

Bondarenko, V., Kovalevs’ka, I. & Ganushevych, K., 2014. Progressive Technologies of Coal, Coalbed Methane, and Ores Mining, Boca Raton, Fla: CRC Press.

Camp, W.G., Heath-Camp, B. & Stokes, A.D., 2016. Managing our natural resources, Stamford: Cengage Learning.

Galvin, J.M., 2016. Ground engineering – principles and practices for underground coal mining, Place of publication not identified: Springer.

He, X. et al., 2014. Progress in mine safety science and engineering II: proceedings of the 2nd International Symposium of Mine Safety Science and Engineering, Beijing, China, 21-23 September 2013, Leiden, The Netherlands: CRC Press/Balkema.

Kesler, S.E. & Simon, A.F., 2015. Mineral resources, economics and the environment, Cambridge: Cambridge University Press.

Li, Y., 2016. The impacts of longwall mining on groundwater systems over thin overburden in a coal mine of appalachia coalfield in United States, Beijing: Metallurgical Industry Press.

& B., 2013. Modern American Coal Mining: Methods and Applications, SME.

Pivnyak, G. et al., 2013. Mining of mineral deposits, Boca Raton, FL: CRC Press.

Riazi, M.R. & Gupta, R., 2015. Amazon.com Find in a library All sellers » Books on Google Play Coal Production and Processing Technology, CRC Press.

Richards, M.J. & Szwilski, A.B., 2012. Underground Mining Methods and Technology, Elsevier Science.

Singhal, R.K., 2014. 21st International Symposium on Mine Planning and Equipment Selection (MPES 2012) New Delhi, India, 28-30 November 2012, Red Hook, NY: Curran.

Singh, P. et al., 2017. NexGen Technologies for Mining and Fuel Industries (Volume I and II), Allied Publishers.

Wain, K., 2014. The Coalmining Industry: Of Barnsley, Rotherham And Worksop, Amberley Publishing Limited.

Woodruff, S.D., 2016. Methods of Working Coal and Metal Mines:Planning and Operations, Elsevier.

Turn in your highest-quality paper
Get a qualified writer to help you with

“ Mining Methods And Risks Evaluation: A Guide ”

Get high-quality paper

NEW! AI matching with writer

Order an Essay Now & Get These Features For Free:

Turnitin Report

Formatting

Title Page

Citation

Outline

Place an Order