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Written test 1, Rock Mechanics > Q1 > Flashcards

Q1 Flashcards

1
Q

What is a mineral? Give some examples!

A

A chemically and physically homogeneous substances in the Earth’s crust

  • Chemical compounds – Quartz (SiO2)
  • Elements – Sulphur (S)
  • Alloys – Electrum (AuAg)
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2
Q

What is a rock type? Give some examples!

A

Aggregates composed of one or several minerals • Granite consists of quartz, feldspar and mica

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3
Q

The rock types can be divided into 3 groups, which?

A
  • Magmatic rocks (igneous) - solidified molten rock (magma)
  • Sedimentary rocks - consolidation through diagenesis of solid material deposited by wind, water or ice.
  • Metamorphic rocks - rocks subjected to increased pressure or temperature transforms through a process called metamorphism
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4
Q

Which properties of the rock types are important from a rock mechanics point of view?

A
  • The rock type
  • Strength (UCS)
  • Structures
  • Weathering
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5
Q

Which types of discontinuities can be found in the rock mass?

A

Fracture plane
Crushed zone
Shear zone

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6
Q

In what way do the discontinuities affect the behaviour of the rock mass?

A

Joints lower the strength of rocks according to the “rule of the weakest link”. Especially the strength of the fracture surface in the direction of the fracture plane, i.e. the shear strength of the fracture.

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7
Q

Which properties of the discontinuities are important from a rock mechanics point of view?

A
  • The roughness of the fracture surface
  • The fracture-filling mineral
  • The fracture width/thickness of the fracture fill
  • The compressive strength of the fracture surfaces
  • Hydrological flow
  • Orientation
  • Length
  • Spacing
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8
Q

Explain how a rock engineering prognosis is done (equivalent to geomechanical model)?

A
  1. Establish objectives, specify accuracy require
  2. Collect existing geological and RM data Preliminary geological prognosis
  3. Define study program based on 1 and 2
  4. Estimate cost
  5. Conduct the pre-investigation as planned Detailed investigation in sensitive areas Present the results
  6. Make rock engineering prognosis based on the results from 5
  7. Continuous follow-up during construction phase
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9
Q

What is a rock mass classification system?

A

• To generate a understanding of the composition and characteristics of the rock mass
• A checklist for important properties to consider
• Used in the preliminary design – updated as the project
continues
• Based on case histories, usually from civil engineering

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10
Q

Mention three classification systems?

A
  • RQD – Rock Quality Designation
  • RMR – Rock Mass Rating
  • The Q-system – Tunnel Quality Index
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11
Q

What can the result of a rock mass classification be used to?

A
  • Determine the strength of the rock mass
  • Estimate the stability of tunnels and slopes
  • Design reinforcement
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12
Q

What is hemispherical projections?

A

A way to illustrate the strike and dip of one or several joints.

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13
Q

How do you get the rock joint data?

A
  • Tunnel mapping
  • Surface mapping
  • Mapping of rock cores
  • Laboratory test
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14
Q

What is strike, dip and dip direction?

A

Strike= Is a value between 0 and 360 degree calculated from the north.

Dip= A value between 0 and 90 degree calculated from the horizontal plane.

Dip direction= perpendicular direction from the Strike ( the strike angel + 90 degrees)

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15
Q

What does the right hand rule mean?

A
  • Thumb = strike
  • Fingers = dip direction
  • Palm=dip
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16
Q

State 2 methods of joint mapping!

A

If you want to assume the stability or hydrological conditions in a tunnel then you should map both the roof and walls.

If the purpose of the mapping is to obtain rock and joint parameters for a classification in a tunnel then you should use line mapping or cell mapping.

Line mapping= only the joints crossing the line are mapped.
Cell mapping= only the joints occurring in the square are mapped.

17
Q

State three characteristic properties from a rock mechanics point of view Magmatic rock types

A
  • High strength
  • Often with a porphyritic texture
  • Can contain dissolved gas and sometimes gas bubbles
18
Q

State three characteristic properties from a rock mechanics point of view for metamorphic rock types

A
  • The most common metamorphic structures are different types of foliation and lineation
  • Fine-grained rocks are schistose while more course-grained rocks are gneissic
  • The strength of metamorphic rock varies greatly
19
Q

State three characteristic properties from a rock mechanics point of view for Sedimentary rocktypes

A
  • Characterized by their parallel stratification or layering
  • Relatively fine-grained
  • Relatively low strength
20
Q

What is important to know about the joints in a rockmass before construction of a tunnel? State at least 4 parameters, both geometrical and physical/mechanical

A
  • The type of joint
  • The roughness of the joint surface
  • The fracture-filling material
  • The joint opening/thickness of the joint fill
  • The strength of the joint surface
  • The hydrological flow
21
Q

Which differences between the following rocktypes are important from a rock mechanics point of view
sandstone – granite?

A

The granite is a rock type with a much higher strength than sandstone.

22
Q

What is JRC a measure of?

A

JRC is measured using a roughness indicator (comb), which gives an imprint of the irregularities of the joint surface.

23
Q

How is JRC measured?

A

JRC is measured using a roughness indicator (comb), which gives an imprint of the irregularities of the joint surface.

Written test 1, Rock Mechanics (1 decks)

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