UNIVERSITY MINOR TEST $1$

APRIL$/$ MAY $2024$

MIN$2605$

Rock Mechanics I

Welcome to MIN$2605$ Minor Test $1$

Date: $17$ May $2024$

Time: $08$:$00$

Hours: $2$hrs

Examiner name: Dr$.$ VC Madanda

Internal moderator name: Mr$.$ NR Mndawe

External moderator name: Dr$.$ AS Nhleko

This paper consists of $08$ pages.

Total marks: $50$

Graduate Attribute: None

Instructions:

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Use a blue or black ink.

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You only have $2$ hours to complete this minor test.

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This is a minor test; therefore, it is not an invigilated assessment.

Additional student instructions

$1.$

Students must upload their answer scripts in a single PDF file $($answer scripts must not be password protected or uploaded as $$read only$$ files$)$

$2.$

Incorrect file format and uncollated answer scripts will not be considered.

$3.$

NO emailed scripts will be accepted.

$4.$

Students are advised to preview submissions $($answer scripts$)$ to ensure legibility and that the correct answer script file has been uploaded.

$5.$

Incorrect answer scripts and$/$or submissions made on unofficial examinations platforms $($including the invigilator cell phone application$)$ will not be marked and no opportunity will be granted for resubmission. Only the last answer file uploaded within the stipulated submission duration period will be marked.

$6.$

Mark awarded for incomplete submission will be the student$$s final mark. No opportunity for resubmission will be granted.

$7.$

Mark awarded for illegible scanned submission will be the student$$s final mark. No opportunity for resubmission will be granted.

$8.$

Submissions will only be accepted from registered student accounts.

$9.$

Students suspected of dishonest conduct during the examinations will be subjected to disciplinary processes. Students may not communicate with any other person or request assistance from any other person during their examinations. Plagiarism is a violation of academic integrity and students who plagiarise, copy from published work or Artificial Intelligence Software $($eg ChatGPT$)$ or online sources $($eg course material$),$ will be in violation

$2$

of the Policy on Academic Integrity and the Student Disciplinary Code and may be referred to

a disciplinary hearing. Unisa has a zero tolerance for plagiarism and$/$or any other forms of academic dishonesty.

$10.$

Listening to audio $($music$)$ and making use of audio$-$to$-$text software is strictly prohibited during your examination session unless such usage of the software is related to a student$$s assistive device which has been so declared. Failure to do so will be a transgression of Unisa$$s examination rules and the student's marks will be withheld.

$11.$

Non$-$adherence to the processes for uploading assessment responses will not qualify the student for any special concessions or future assessments.

$12.$

Queries that are beyond Unisa$$s control include the following: a$.$ Personal network or service provider issues

b$.$ Load shedding$/$limited space on personal computer

c$.$ Crashed computer

d$.$ Non$-$functioning cameras or web cameras

e$.$ Using work computers that block access to the myExams site $($employer firewall challenges$)$

f$.$ Unlicensed software $($eg license expires during exams$)$

Postgraduate students experiencing the above challenges are advised to apply for an aegrotat and submit supporting evidence within ten days of the examination session. Students will not be able to apply for an aegrotat for a third examination opportunity.

Postgraduate$/$undergraduate students experiencing the above challenges in their second examination opportunity will have to reregister for the affected module.

$13.$

Students suspected of dishonest conduct during the examinations will be subjected to disciplinary processes. UNISA has a zero tolerance for plagiarism and$/$or any other forms of academic dishonesty.

$14.$

Students experiencing network or load shedding challenges are advised to apply together with supporting evidence for an Aegrotat within $3$ days of the examination session.

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Question $1$: Basic theory & definitions of rock mechanics

$1\mathrm{.}1.$

Define the following terms and concepts, give their units of measurements where applicable.

$1\mathrm{.}1\mathrm{.}1.$

Principal stress $(2)$

$1\mathrm{.}1\mathrm{.}2.$

Shear Stress $(2)$

$1\mathrm{.}1\mathrm{.}3.$

Deformation $(2)$

$1\mathrm{.}1\mathrm{.}4.$

Displacement $(2)$

$1\mathrm{.}2.$

Classify the following rock sample: Granite. $(2)$

$1\mathrm{.}3.$

Describe the importance of mineral content, texture, fabric, and mineral alteration in determining the properties of rock. $(4)$

$1\mathrm{.}4.$

Explain how the Mohr failure envelope is used to understand rock failure. Use sketches to elaborate your answer $(6)$

$1\mathrm{.}5.$

Consider a rock mass with a density of $2750$ kg$/$m$3$ where mining is to take place at a depth of $1500$ m below the surface. What is the primitive stress? $(2)$

$1\mathrm{.}6.$

Calculate the K ratio of a gold mine situated $2750$ m below the surface in quartzite if the horizontal stress component is based on the following equation: $()\backslash$cong $10+(0\mathrm{.}01$ x h$)(3)$

$[25]$

$4$

Question $2$: Stress analysis in two dimensions $(2$D$)$

$2\mathrm{.}1.$

The $2$D virgin stress tensor as measured at a po