Q. The immediate roof of a mine is supported by bolts of length 1.5 m, arranged in 1.2 m x 1.2 m grid pattern. If the unit weight of roof rock is 2.25 tonne/m3 and load carrying capacity of each bolt is 7.5 tonne, the factor of safety of the support system is       . Ans: 1.4-1.6

Q. In underground face blasting, the pull is found to be 10% less than the drillhole length. The headings of 3.6 m width are supported by prop density of 1.44/m2. The hole length is 1.5 m, and 6 rounds of blasting are done in the panel per shift. The number of props to be erected in a shift ...

Q. The experiment to determine permeability of a soil sample is illustrated below. The cross- sectional area of the sample is 20.0 cm2. The permeability of the soil sample in cm/s is Ans: 0.02-0.02

Q. An SDL of 1.0 tonne capacity operates with a cycle time of 6 minutes. The dimension of the face is 4 m x 3 m. Five blasts are conducted per shift with an average pull of 1.2 m. If the density of blasted coal is 0.8 tonne/m3, the time required by the SDL in the shift to lift all the prepared ...

Q. In a direct rope haulage operating along a 1500 m long incline, 180 tonne of coal is hauled in 7 hours. The average rope speed is 7.5 km/h. The set changing time for the tubs is 2 minutes each at the top and bottom of the incline. If the tub capacity is 1.0 tonne, the number of tubs in the set ...

Q. Air enters a bord and pillar panel at 10 ppm CO and 20.78% O2. The air at the panel return has 80 ppm CO and 20.52% O2. The ‘Graham’s ratio’ for the status of fire in the panel in % is                  Ans: 2.65-2.75

Q. A person standing 50 m away from an HEMM experiences 90 dB sound pressure level. If the person moves to a new location that is 70 m away from the HEMM, the sound pressure level experienced by the person, in dB, becomes _        Ans: 86.75-87.25                        .

Q. 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) 780                       (B) ...

Q. A system of two identical components connected in series has reliability of 0.25. The reliability of each component is Ans: 0.5-0.5

Q. 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   Ans: 16.0-16.0

Q. For the conveyor belt drive shown, the tension on the tight side (T1 ) is double that of the slack side. The coefficient of friction between belt and drum is 0.21. The minimum angle of lap (in degree) to avoid slippage of the belt is                                       . Ans: ...

Q. The RL of the initial station is 200 m. If Σ BS = 1.54 m of the last station in m is  and Σ FS = 0.45 m , then the RL. Ans: 201.09-201.09                                 .