In a bord and pillar development district, 6 headings driven along the strike direction are surrounded by panel barriers on the dip and rise sides. The maximum possible number of faces for the panel is ______.
A system of two identical components connected in series has reliability of 0.25. The reliability of each component is ______.
If is a constant, the solution of the differential equation is
A panel in coal mine produces 400 tonne per day. The number of persons employed in each of the three shifts is 110, 130 and 120. As per CMR, the minimum quantity of air that needs to be circulated at the last ventilation connection of the panel in m³/min is
A right conical iron ore stack on level ground of height 10 m has 60% Fe. The height of the conical stack is extended up to 20 m using iron ore of 50% Fe. The angle of repose of iron ore is 38°. The mean grade of the final stack in % Fe is ______.
Economic feasibility of two methods is examined for meeting a targeted mine production. On a yearly basis, the following cost parameters (Rs in crores) are applicable for these methods.
| Method 1 | Method 2 | |
|---|---|---|
| Fixed cost | 20 | 5 |
| Variable cost | 2X | X² |
The annual rate of production, ‘X’ in million tonnes for which both the methods will yield the same operating cost is ______.
The radial stress concentration around a long circular tunnel excavated in rock is given by the curve
The correct figure depicting the extraction of contiguous seams in bord and pillar working is indicated by
From a coal seam of a mine 1000 tonnes of coal is produced per day. The seam has inflammable gas emission rate of 14000 per day. Percentage of inflammable gas in general body of air is 0.14. The gassiness of the seam is
Out of the support categories given for an underground coal mine, identify the ‘active support’.