Winning and Working - Questions from DGMS and PSU Exams

Question

A mine void of dimension 100.0 m x 2.0 m x 1.2 m is to be filled in 3 hours by hydraulic stowing. The sand to slurry ratio is 0.4. If the hydraulic fill factor is 0.9. the hourly consumption of water for the operation, in m3, is ____ (rounded off to 2 decimal places.

Solution

Vmine void​=100.0 × 2.0 × 1.2 = 240.0 m3

Vsand​ = Vvoid​ × fill factor

= 240.0 × 0.9

= 216.0 m3

Vslurry = Vsand/0.4 = 216/0.4 = 540 m3

Vwater = Vslurry  - Vsand

= 540 - 216 = 324 m3

Hourly water consumption

= 324/3 = 108 m3

These questions are taken from study material for mining engineering exams (DGMS and PSU) by amiestudycircle.com. WhatsApp channel: Miners Adda 

Question

Following information are given for three mines of a company receiving explosives from three suppliers.

Considering the initial basic feasible solution of this transportation problem, using North-West comer method, the transportation cost of explosives supplied to the company, in Rs., is

(a) 90000

(b) 109000

(c) 293500*

(d) 385000 

Solution

See following figure which is self explanatory.

Cost = 10 x 1000 + 15 x 1500 + 2 x 500 + 100 x 2000 + 20 x 3000 

= ₹ 293500

Also read: 

Numerical problems from Mine Surveying from DGMS and PSU Exams

Numerical problems from Mining Machinery from DGMS and PSU Exams 

Numerical problems from Mine Ventilation from DGMS and PSU Exams 

Question

In a bord and pillar panel, the following data are obtained.

Number of blasting rounds per shift : 8

Face dimension (m x m) : 4.2 x 2.5

Average pull (m) : 1.2

Specific gravity of coal : 1.4

Manpower per shift : 100

The OMS (output per manshift) of the panel, in tonne, is ____ (rounded off to 2 decimal places).

Solution

Total volume of coal

= Number of shifts x gallery width x gallery height x Average pull x Number of faces x number of rounds

= 1 x 4.2 x 2.5 x 1.2 x 1 x 8 = 100.8 m3

Weight of coal/day

= volume x density

= 100.8 m3 x 1.4 = 141.12 t

OMS = weight per day/total manpower

= 141.12/100 = 1.41ton

These questions are taken from study material for mining engineering exams (DGMS and PSU) by amiestudycircle.com. WhatsApp channel: Miners Adda 

Question

A triaxial test on a sandstone sample is conducted at a confining pressure of 10 MPa. The elastic axial and volumetric strains at axial stress of 50 MPa are recorded to be 4.2 x 10-3 and 2.0 x 10-3 respectively. The modulus of elasticity, in GPa. and Poisson’s ratio of the sample, respectively are closest to

(a) 5.11.0.35

(b) 10.22,0.35*

(c) 5.11.0.17

(d) 10.22.0.17 

Solution

Young modulus (E)
=  ∆σ/elastic axial strain

= (50 - 10)/(4.2 x 10-3)

= 9524 MPa = 9.52 GPa

Poisson ratio

ν = (1/2)[1 - (εv/εa)]

= (1/2)[1 - (2 x 10-3/4.2 x 10-3)]

= 0.26

Also read: 

Numerical problems from Mine Surveying from DGMS and PSU Exams

Numerical problems from Mining Machinery from DGMS and PSU Exams 

Numerical problems from Mine Ventilation from DGMS and PSU Exams 

Question

In a development coal face, 12 holes are drilled and charged with explosive. Holes are initiated with electric delay detonators connected in series. The length of a detonator lead wire is 1.5 m. The length of the blasting cable is 120 m.

Data are as given:

Resistance of each detonator: 1.48 Ω

Resistance of lead wire: 0.04 Ω/m

Resistance of one wire of the blasting cable: 0.009 Ω/m

The total resistance of the circuit in Ω, is ____ (round off up to 2 decimals).

Solution

There are two blasting wires, 12 lead wires and 12 detonator.

Resistance of blasting wire 

= 2 x 0.009 x 120

= 2.16 Ω

Resistance of 12 lead wires 

= 12 x 0.04 x 1.5

= 0.72 Ω

Resistance of 12 detonators in series 

= 12 x 1.48 = 17.76 Ω

Total resistance = 2.16 + 0.72 + 17.76

= 20.64 Ω

These questions are taken from study material for mining engineering exams (DGMS and PSU) by amiestudycircle.com. WhatsApp channel: Miners Adda

Question 

A surface coal mine is worked by 10 m3 shovel – 85 tonne dumper combination. If the shovel bucket fill factor is 0.8, the material swell factor is 0.75 and the average in-situ sp.gr. of the material is 3.5 tonne/m3, the number of shovel bucket loads required to fill a dumper will be nearly____.

Solution 

Bucket loose volume  = 10 x 0.8 = 8 m3

This is Volume of material as it sits in the bucket (before swelling).

In-situ weight of material per bucket

= 8 x 3.5 = 28 tonnes

Number of loads = dumper capacity/(swell factor x in-situ weight)

= 85/(0.75 x 28) ≈ 4

The swell factor usually means that the loose volume taken by the shovel is less than the in-situ volume.

These questions are taken from study material for mining engineering exams (DGMS and PSU) by amiestudycircle.com. WhatsApp channel: Miners Adda
Question 

What would be the capacity of a flat belt conveyor in ton/ hour, if the bulk density of material is 0.8 t/m3, belt width is 1.0 m, angle of repose is 45° and velocity is 100 m/min? 

Solution  

T = abv

= (1/2)(width x pile height) x b x v

where b is bulk weight and v is velocity.

 
Pile height = 0.5 tan450 = 0.5 m x 1 = 0.5 m

T = (1/2)(1 m x 0.5 m) x 0.8 t/m3 x (100 x 60 t/hr) = 1200 t/hr

Question

An explosive with a density of 1.2 g/cm3 has a heat of explosion equal to 900 cal/g. If the heat of explosion of ANFO with density of 0.8 g/cm3 is 950 Cal/g, the bulk strength of the explosive relative to ANFO is _____. (round off up to 2 decimals)

Solution

Relative bulk strength

= str1 x SG1/stranfo x SGanfo

= 900 x 1.2/(950 x 0.8)

= 1.42

These questions are taken from study material for mining engineering exams (DGMS and PSU) by amiestudycircle.com. WhatsApp channel: Miners Adda 

Question

A rectangular development heading of dimension 3 m × 2.8 m is to be blasted with holes of 2.4 m in length. If the pull factor is 0.95 and swell factor is 1.20, the volume of blasted rock per round, in m3, is______. (round off up to 2 decimals).

Solution

Volume of blasted rock = H x W x L x pull factor x swell factor

= 3 x 2.8 x 2.4 x 0.95 x 1.2

= 22.98 m3

Also read:

Numerical problems from Mine Surveying from DGMS and PSU Exams

Numerical problems from Mining Machinery from DGMS and PSU Exams 

Numerical problems from Mine Ventilation from DGMS and PSU Exams  

Question

A Bord and Pillar panel is developed at a depth of 250 m in a flat coal seam. The vertical stress gradient is 0.027 MPa in. If the strength of [a square pillar is 12.5 MPa. the extraction ratio of the pillar for a safety factor of 1.5. is ____ (round off up to 2 decimals). 

Solution 

Load on pillar = vertical stress gradient x depth x [(a +b)/a]2

= 0.027 x 250 x [(a + b)/a]2 MPa

= 6.75 x [(a + b)/a]2 MPa

Strength of pillar = 12.5 MPa

Now, factor of safety = strength of pillar/load on pillar

∴ 1.5 = 12.5/[(a + b)/a]2

Giving [(a + b)/a]2  = 1.23

Now extraction ratio = 1 - [a/(a + b)]2

= 1 - (1/1.23) = 0.18

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