unsw intro mining test

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Examination for the Bachelor of EngineeringSchool of Civil & Environmental Engineering)

Semester 2, 2009

Course ID: 103962 INTRODUCTION TO MINING ENGINEERING(Undergraduate)

C&ENVENG 1011

Official Reading Time:Writing Time:Total Duration:

10 mins120 mins130 mins

Instructions for Candidates

This is a closed-book examination. No course materials (lecture slides, textbooks, notes) can be

brought into the exam Please, ANSWER ANY FOUR (4) OF THE SIX QUESTIONS; the questions are of equal marks. Each

question has multiple parts that should be answered.

Your exam question paper must be submitted together with your exam answer booklets. Make sureyou complete the details at the top-right corner of this page.

Show all calculations and assumptions. If you believe that a parameter or an important piece of information has been inadvertently omitted by

the examiner, assume a suitable value, clearly stating it, and continue with the solution.

Write your answers clearly in your exam booklet, clearly mark the question number, e.g., Question 1 Part b. Illegible writings will not be marked.

Permitted Materials

The use of calculators is permitted, this equipment to be supplied by the candidate. No pre-recordedmaterial or calculator instruction book is permitted, and calculators with remote communication linkswill be barred from the examination room.

DO NOT COMMENCE WRITING UNTIL INSTRUCTED TO DO SO

Student ID:__________________________

Family Name:________________________

Other Name:________________________

Desk:______________________________

Date:______________________________

Exam Mark:_________________________


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Course ID: 103962 Page 2 of 9


QUESTION 1 (25 marks)MINING GEOLOGY AND RESOURCE ESTIMATION

a) Draw the diagram showing the relationship between exploration information, mineralresources and ore reserves according to the JORC Code; write a brief definition ofeach category of mineral resources and ore reserves. [8 marks]

b) A diamond drill hole coring 3-m runs intersected the hanging wall of a vein at 19.5mand went into the footwall 28.3m. A high grade zone was noted between the 23 and25-m interval. The core was split and assayed as shown in Table 1. Complete thetable (distance column) and estimate the weighted average assay value for this

intersection. [7 marks]Table 1Core Assay

From (m) To (m) SampleLength (m)

Assay (g Au/t)

19.5 21.3 10.721.3 23.5 8.923.5 24.4 19.224.4 25.1 21.025.1 27.4 13.127.4 28.3 7.6

c) ABC Mining Pty Ltd has finished exploration for a near surface polymetallic deposit.The deposit contains copper, zinc, silver and gold. Calculate the Unit Value for thisdeposit. [6 marks]

Metal Grade Metallurgical.recovery

Metal Price Unit Value($/t ore)

Copper 0.8% 85% A$8000/tonneZinc 3.1% 80% A$1600/tonneSilver 30g/t 90% A$1.00/gramGold 2g/t 90% A$40/gram

d) List the names of four methods used in resource/reserve estimation. [4 marks]


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QUESTION 2 (25 marks)

MINE PLANNING

The following data are given for a mineral deposit occurring under conditions similar tothose shown in Figure 1. You may use the equations in Appendix 1.

surface

OverburdenV

e=1

h

d

L

A

m

n

OreW

t

b

1m

v

w

Figure 1: Simplified geometric representation of the pit parameters and SRmax at pit limit

Value of ore = $5.29/tonne Costs (excluding stripping) = $3.64/tonne) Stripping costs (for overburden of e=1) = $0.26/m3) Berm dimension, a = 0 Dip of deposit = 20o Pit slope = 60o Deposit thickness t =15.2m Equivalent yardage e=2 Tonnage factor TF = 0.47m3/tonne

a) Calculate the maximum allowable stripping ratio, SRmax. Where does this ratioapply? [5 marks]

b) Locate the pit limits for the deposit (specify h = vertical depth to the deposit andd = horizontal distance along the surface to the outcrop) [10 marks]

c) Calculate the overall stripping ratio, SRo in mining the ore body by surfacemethods. [5 marks]

d) What is meant by the term stripping allowance? [5 marks]


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QUESTION 3 (25 marks)MINING METHODS

a) What are the three basic surface mine designs? [3 marks]

b) What are the disadvantages and advantages of surface mining? [4 marks]

c) Draw a vertical cross-section through an open pit mine at a certain stage in its life andshow these features: bench, toe, crest, berm, bench angle, overall slope angle, pitfloor, haul road and bench height. [5 marks]

d) List one major advantage and one major disadvantage of each of the followingunderground mining methods: [5 marks] Room and pillar

Sublevel stoping

Block caving

Long wall

e) List three types of underground and two types of surface mining equipment and brieflydescribe their functions. [5 marks]

(f) Mining methods used in metal mines are more varied than those used in coal mines why do you think that is? [3 marks]

QUESTION 4 (25 marks)MINE DEVELOPMENT AND ROCK BREAKAGE

a) With the aid of sketches, write short notes on each of the following common methodsof mine access: (i) Shaft, (ii) Decline; (iii) Adit. What factors influence the choice ofeach method? [5 marks]

b) List three major types of explosives commonly used in todays mining operations.Give one major advantage and one major disadvantage for each explosive listed.

[5 marks]c) What are blasting caps? List three types of blasting caps and give one majoradvantage and one major disadvantage for each explosive listed. [5 marks]

d) Rock breakage by explosion is caused by two major explosion actions. What arethey? Give a brief description. [5 marks]

e) Briefly describe the environmental impacts of blasting and ways to minimise theimpacts? [5 marks]


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QUESTION 5 (25 marks)MINERAL PROCESSING

a) Define the following terms: [5 marks]

i. Tailings

ii. Middlings

iii. Head grade

v. Reduction ratio

b) List the names of three types of physical concentration and two types of commonlyused chemical concentration: [5 marks]

i. Physical concentration:

ii. Chemical concentration:

c) Describe the use of the following equipment in the mineral processing plant:[10 marks]

i. SAG Mill

ii. Hydrocyclone

iii. Scavenger

iv. Thickener

v. Pressure filter

d) List the common steps involved in the smelting and refining of the following metals (nodetailed explanation necessary): [5 marks]

i. Lead

ii. Copper

iii. Iron Ore


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QUESTION 6 (25 marks)MINING GEOMECHANICS AND MINE VENTILATION

a) Give definitions of uniaxial compressive strength, elastic modulus and Poissons ratio.What are the units of these three parameters? [5 marks]

b) Figure 2 below was obtained from a uniaxial compressive test on a rock from a mine.The graph shows the response of axial strain and lateral strains against the axial forceapplied on a cylindrical rock sample whose diameter is 5.4 cm and length is 10.0 cm.What are the uniaxial compressive strength, elastic modulus and Poissons ratio of therock measured from the above experiment? Use the relevant units when necessary.

[10 marks]

Figure 2: Uniaxial compressive test result

c) List 5 major types of air contaminants in underground mining operations that must beremoved by ventilation: [5 marks]

d) Give a brief account of the three types of radiations generated by the decays of heavyelements. [5 marks]


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APPENDIX 1To determine the ultimate pit limit, one needs to calculate the maximum stripping ratio (SRmax), also knownas the Breakeven Stripping Ratio (BEVSR). This ratio is based solely on mining economics.

Mathematically,

coststripping

costproduction-oreofvaluemax =SR (1)

RELATIONSHIP FOR MAXIMUM STRIPPING RATIO AND PIT LIMITS

Referring to Figure 1:

t = deposit thickness (m)

= dip of deposit (degrees)

m = inclined length of the deposit to the pit limit (metres) ; measured to toe of the bank

= pit slope (degrees)

L = inclined length of pit slope (m)

h = vertical length of the inclined pit slope (m)

d = horizontal distance from outcrop to pit limit (m); measured to the crest of the bank

Assume:

thickness of the cross-section = 1

V = Overall volume of overburden

W = Overall weight of the ore

The volume of overburden removed = v

The tonnage of ore recovered = w

TF = tonnage factor of ore (m3

/tonne)

Lbv = 0.1 (2)

TF

tw

=

0.10.1(3)


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The ratio of the two is the maximum allowable stripping ratio:

TFt

Lbe

w

vSR

/max

== (4)

e = equivalent yardage: allows one to use the equation when different rock types are present.

Determine b:

18090 =+++o

Therefore;

( ) == 090coscos0.1b (5)

Recall: SRmax is calculated using the economic relationship in equation (1). Therefore, one candetermine L by rearranging equation (4) as follows:

TFbe

SRtL

=

max

(6)

Using trigonometry, determine the vertical height of the pit slope, h

sin= Lh (7)

Assuming a berm width = a, as a safety measure, determine the horizontal distance d fromoutcrop m.

tantan

hhad ++= (8)

Finally, the inclined length of ore from the outcrop m is:

sin

hm = (9)


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END OF EXAMINATION

DETERMINATION OF OVERALL STRIPPING RATIO

From Figure 2:

dhV =2

10.1 (10)

TF

tmW

=

0.1(11)

Hence, the Overall Striping Ratio is:

TF

tm

dh

W

VSR

o

==2

1

(12)

The above equation (12) ignores area A in Figure 2. The area must calculated and added to W.

unsw intro mining test

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