The extraction ratio during development of a bord and pillar panel is 0.15 in a flat coal seam. The panel is further extracted by widening the galleries, and the extraction ratio changes to 0.25. The percentage change in pillar stress, considering tributary area method, is______. (round off to two decimal places)

A pump lifts mine water of density 1020 kg/m³, at 250 m³/hr from a depth of 150 m. The overall pumping efficiency is 68%. Considering a head loss of 15 m due to pipe friction and shock, the motor input power, in kW is______. (round off to two decimal places)

In a longwall face, the full seam thickness of 3 m is cut by a shearer with a web of depth 0.7 m. The hauling speed of shearer during cutting is 12 m/min. The trough cross-section of AFC is 0.4 m² and the average loading coefficient is 0.7. In order to evacuate coal from the face without spillage, the speed of AFC, in m/s is ______. (round off to one decimal place)

A city is spread over an area of 20 km × 40 km. Wind, at an average speed of 4 m/s, enters perpendicular to the 20 km long side. On a winter day the inversion layer exists over the city at a height of 100 m. PM₁ is emitted from the city at a rate of 1 kg/s. The steady state PM₁ concentration in the city air, in µg/m³, assuming Box model, is ______. (round off to one decimal place)

An underground workshop has dimensions of 8 m length, 6 m width and 4 m height. Four identical luminaires are placed at the four corners of the roof. Each luminaire is of 100 W capacity with luminous efficacy of 100 lumen/W. Light is transmitted spherically from luminaires and there are no reflections. The illumination on the horizontal plane at the centre of the floor, in lux is ______. (round off to two decimal places)

An underground AC plant requires the delivery of 250 US gpm (15.85 US gpm = 1.0 lps) of chilled water. For this purpose, ice-pellets at 0 °C temperature (latent heat of melting, 334 kJ/kg) are mixed with water at 20 °C (specific heat 4.18 kJ/kg°C) on the surface. The mixture is adiabatically transported to the underground location such that the water at 7 °C becomes available for the AC plant. The requirement of ice-pellets in tonne/hr to meet the design condition, is ______. (round off to two decimal places)

An intake shaft has resistance of 0.05 Ns²/m⁸ up to a depth of 400 m. The airflow rate is 100 m³/s and the average density is 1.2 kg/m³. A barometer reads 99.375 kPa when placed on surface. Considering acceleration due to gravity is 9.81 m/s², the reading of the barometer at the depth of 400 m, in kPa is ______. (round off to two decimal places)

Let $\frac{dT}{dt} \propto (T_R - T)$, where $T_R$ and $T$ are temperatures in degree centigrade of a room and thermometer, respectively, and $t$ denotes time in minutes. A thermometer at a reading of 2°C is brought in a room of temperature 40°C. Two minutes later, the thermometer reads 15°C. The time elapsed in minutes when the thermometer reads 39.5°C, is ______. (round off to two decimal places)

Following information is given for a drilling operation to be carried out for overburden removal in a surface mine.

Volume of rock blasted per round, m³ : 3,20,000

Number of blast holes : 100

Drill hole diameter (D), mm : 200

Length of subgrade drilling : 8D

Stemming length : 25D

Bench height, m : 30

Powder factor, m³/kg : 3.2

The amount of explosive per unit length of charge in kg/m, is_______.
(round off to two decimal places)

The oxygen-balanced equation for explosive ANFO is given below.

$3NH_{4}NO_{3}+CH_{2}\rightarrow7H_{2}O+CO_{2}+3N_{2}$

For 100 litre of fuel oil having density 850 kg/m3, the amount of ammonium nitrate to be mixed, in kg, is_______. (round off to two decimal places)