DEPARTMENT OF MINERALS AND ENEGRY MINE MANAGERS EXAMINATION COAL MINING II

Transcription

1 DEPARTMENT OF MINERALS AND ENEGRY MINE MANAGERS EXAMINATION COAL MINING II DATE: 12 NOVEMBER 1997 TOTAL MARKS: 100 TIME ALLOWED: 3 HOURS TO PASS: 50 (08:30 11:30) NOTE: All five questions must be answered. All sketches and answers to be presented in a neat and decipherable manner.

2 1 QUESTION 1 VENTILATION 1.1 Describe in detail the advantages and disadvantages of coursing and splitting methods of ventilation to ventilate the face region of a bord and pillar section. (12) 1.2 With reference to the guideline for a code of practice for the ventilating of mechanical miner sections, state the following requirements The minimum last through road velocity; The minimum quantity of fresh air to be supplied to the heading being advanced; The maximum percentage re-circulation permitted; and Minimum air velocity passing over the operators cabin position on the continuous miner. (4) 1.3 Illustrating your answer using the enclosed sketch, describe the coursing ventilation system you will apply to comply with the requirements stated in 1.2 above. The intake velocity (Vi) must be stated. (4) [20] QUESTION 2 Rock Engineering A continuous haulage system is to be implemented. The pillar design has subsequently changed to adapt to the new technology. The square pillars have made way for 60 pillars. To calculate the safety factor for these pillars the effective width should be used. Applicable formula: Effective width: We = C 4A Where C = Circumference A = Area σ Pillar Strength SF = -- = Pillar Load L 2.1 A continuous miner using a continuous haulage mined the pillar illustrated below. Given the following information, calculate the safety factor. (10)

3 2 Depth to floor = 130 m Mining height = 3.0 m Centres (C x C) = 25 m x 20 m Bord widths (B)= 6.5 m 2.2 Briefly comment on the rock mechanic considerations on the mining layout illustrated above. (5) [15] QUESTION 3 Environmental Management You are the Manager at a coal mine where total extraction (longwall mining method) is being practiced. At the mine a problematic situation exists with underground water in the goaf area. The situation is as follows (refer to figure 3.1): An area of ha has been mined on the shallowest seam. The groundwater table has been drawn into the mine. Boreholes into the goafed area indicated the water table at an average depth of 36.5 m from surface. Laboratory analysis of water samples from the goaf area indicate the Sulphate concentration to be 120 mg/l.

4 3 Reports done for the mine on areas of total extraction indicate the following: 1. The average porosity for goaf material is 35 %. 2. In a goaf area 5 kg of Sulphate per hectare is produced every day. 3. The average water make for the goaf (i.e. recharge water via surface and groundwater) is 5Ml per day. The average Sulphate concentration of this recharge water is 40mg/l. Determine: 3.1 The volume of water currently in the goaf. (5) 3.2 The volume of water in the goaf by the end of the year Note: No additional mining has taken place during this period. (Take 1 st of January 1998 as a starting date use 365 days per year throughout the exercise). (4) 3.3 The Sulphate concentration in mg/l of the water in the goaf by the end of the year (Take the 1 st of January 1998 as a starting date and use 365 days per year throughout the exercise). (9) 3.4 Taking cognizance of your answer in 3.3 and the related environmental impacts, what actions should you take? (2) QUESTION 4 [20] Health and Safety Section 12 of the Mine Health and Safety Act states: 12. (1) The manager must engage the part-time or full-time services of a person qualified in occupational hygiene techniques to measure levels of exposure to hazards at the mine- (a) if required to do so by regulation or a notice in the Gazette; or (b) if, after assessing risks I terms of section 11(1), it is necessary to do so. (2) Every system of occupational hygiene measurements must- (a) be appropriate, considering the hazards to which the employees are or may be (b) exposed; and be designed so that it provides information that the manager can use in determining measures to eliminate, control or minimise the health risks and hazards to which employees are or may be exposed. (3) The manager must keep a record of all occupational hygiene measurements in terms of subsection (1) in a manner that can be linked as far as practicable to each employee s records of medical surveillance.

5 4 1. Referring to subsection (b) of 12.(1) what health risks are or may employees be exposed to? (5) 2. How will you, as the manager, ensure compliance with subsection (2) (a) and (b)? (10) 3. How will you, as the manager, ensure compliance with subsection (3)? (5) [20] QUESTION 5 Coal Processing 5.1 What do you understand by proximate analysis? (2) 5.2 Which constituents are determined during the proximate analysis? Describe briefly the method to determine each. (5) 5.3 What is meant by coal preparation? (3) 5.4 What minimum information is required in order to design a coal preparation plant? (5) Sketch the typical flowsheet of a coal preparation plant for a captive mine supplying coal to a power station and general trade. (5) Describe the operation of the plant. (5) [25] TOTAL MARKS [100]

6 Question 1.3 Enclosed sketch Insert this sketch into your answer book Examination Number: