Engineering Geology: Cliff Instability In Rockmass Flashcards
What are three fast types of mass movement?
Rock slide, rock topple, rock avalanche
Name two slow types of mass movement.
Rotational slump, soil creep
Which of the following mass movements are associated with wet conditions?
A. Rock slide
B. Mudflow
C. Soil creep
D. Heave
B. Mudflow
C. Soil creep
What two global statistics are shown to highlight the impact of landslides?
Number of landslides and fatalities due to landslides
What are some causes of mass movement?
Weathering, geological structure, rainfall, slope angle, seismicity
What are three physical properties that influence rock strength?
UCS (Unconfined Compressive Strength), porosity, friction angle
Granite typically has a UCS of about ___ MPa and a friction angle of ___°.
200 MPa; 55°
T/F: Shale has lower tensile strength and friction angle than Granite.
True
What structural geological feature characterises the Møns Klint Thrust Sheet?
Imbricate fan
What did the 2012 Dorset landslide example demonstrate?
The human cost of not engineering unstable cliffs
What are the four key steps to assess and address cliff instability risk?
- Hazard
- Vulnerability
- Risk
- Mitigation
When does a coastal hazard become a true hazard?
When it poses a threat to human life or infrastructure.
Why is vulnerability necessary for risk to exist?
Without people or infrastructure exposed to hazard, there is no risk.
What is the basic formula for risk assessment?
Risk = Hazard × Vulnerability
What geographical region is shown as an example of cliff erosion?
Chalk coastline of southern England
Name three engineering methods to mitigate cliff collapse.
Netting, sea walls, rock bolting
Why is understanding structural geology key even along protected coastlines?
Because failures can still occur, as shown by Peacehaven and Brighton events.
What zones must be assessed to understand cliff hazard?
Cliff top, cliff face, and cliff base/wave-cut platform
What structural feature controls vertical collapses at Seven Sisters cliffs?
Vertical joint sets
What makes failures at Beachy Head complex?
Multiple chalk formations with different joint styles and high cliffs.
What are the 4 stages in the cliff decay cycle?
- Collapse and apron formation
- Apron removal
- Weathering and minor failures
- Large-scale collapse
What failure type is unique to very high or porous chalk cliffs?
Flow slides
List three key aspects affecting chalk cliff engineering.
Lithostratigraphy, rock mass character, geomorphological setting
What is the standard formula for Factor of Safety (F) in slope analysis?
F = Strength / Stress
What is a key disadvantage of using F in limit equilibrium analysis?
It does not identify failure mode or mechanism.
