Geotechnical and geological hazards Flashcards
How do you calculate RQD?
SUM (rock pieces over 10cm) / total core run * 100
Why could the RQD drop after extraction?
Rocks can dry out and fall apart
What are some of the failures in rocks and soils?
- Settlement
- Heave
- Liquefaction
- Bearing capacity
- Factors of safety
- Serviceability Limit State vs Ultimate Limit State
What is Serviceability Limit State?
The state of design beyond which a structural system loses operationally its serviceability for the actual service load that the structure is subjected to. → squishes down
What is Ultimate Limit State
ULS focuses on the safety of the structure under extreme conditions
- Factors of safety
What are mechanisms of failure?
- Compaction
- Landslide
- Caven, cavity
What are the types of slope failures and landslides?
- Rock fall
- Planar Slide
- Wedge failure
- Rock Topple
- Block slide
- Mud flow
What characteristics of the rock can lead to failures?
- Rock type - soils
- Joints
Why is the strength of the material not constant?
- If you were to rotate the planes then FS changes as resistance changes
- Rotation determines whether its safety will be compromised
What is anisotropy?
The quality of exhibiting properties with different values when measured along axes in different directions.
How could you decrease risk of rock slide?
Reinforcing the slope perpendicular to the bedding planes
What failure could occur in tunnels?
Pressure on tunnel and encloses the tunnel
What do rock bolts stabilise?
- road cuts
- rock cliffs
- steep slopes
- bridge abutments
- reinforced concrete dams
Where should rock bolts be positioned?
Positioned where the slide happens and must go beyond the height of the slope - perp to bedding plane
What holds the slide in place when using rock bolts?
By being under tension you are applying a normal force on the face plate
