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39 Cards in this Set

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What does gravity cause?
The downward movement of landslides and subsiding ground.
What are some external causes of slope failure?
1) Steepeing the slope by faults or fault movements.
2) Removing support from low on the slope.
3) Adding mass high on the slope as in sediment deposition.
What is the cause of a landslide?
Loading the head and reducing the toe.
What is an internal cause of slope failure?
Inherently weak materials such as clay.
Whats the problem with clay?
It is too small, and too thin and weathers easily under low pressure and low temperature.
Where is most feldspar found and how is it formed?
Found in granite and is formed under high pressure and temperature.
How does unloading occur?
Clay breaks off through weathering and pressure is removed.
What does the mechanical stregnth of rock depend on?
10-15% of the rock with the smallest grain size.
What is another internal cause of slope failure?
Water
What are some roles of water?
It is absorbed and adsorbed by clay materials. Since it is polar it can be effected electrostatically.
How does water cause slope failure?
Water can dissolve some of the minerals that bind rocks as well as eroding loos materials.
How does water weaken earth materials?
1) Decreasing cohesion
2) Subsurface erosion
3) Creating pressure in pore spaces.
4) Weight
5) Interplay of clay materials
What is another internal cause of slope failure?
Decrease in cohesion
What is the final internal cause of slope failure?
Adverse geologic structures.
What triggers mass movements?
Heavy rains, Earthquakes, Thawing frozen ground, construction projects of humans.
What is the slowest but most widespread type of mass movement?
Creep
What is creep and where are its effects most noticible?
Movement of soil and upper most bedrock, its effects are most noticible on trees and fences.
How does rock and soil move by creep?
Expansion and contraction, the soils swell and then shrinks
Why is the contraction occuring?
Because of the pull of gravity
What is the shrinking caused by?
The soil thawing, drying, cooling and gravity pulling.
What is a fall?
Elevated rock masses seperate along joints, bedding or other weaknesses.
What are the main causes of a fall and how does it ususally occur.
Gravity, earthquakes and people, occurs extremely rapidly and under dry conditions.
What are slides? What is the main cause of them.
Movements above one or more failure surfaces. Gravity is the main cause.
What is a rotational slide and how does it typically occur?
Slump is a roational slide in which the head moves down and typically backwards.
What are transitional slides?
Masses that move down and out by sliding on surfaces of weakness.
What are the three outcomes of transitional slides?
1) They remain basically coherent.
2) They may deform and disintegrate.
3) They may spread laterally when the underlying material fails and flows.q
How do flows behave and what are some different types of them?
They move like fluids, names for them are Loess flow, earthflow, mudflow, debris avalanche, lahars.
In what ways do avalanches move?
Creep, fall, slide and flow
How do avalanches occur?
From triggers such as earthquakes or people, accumulation high on the slopes loads the head and sets the stage for failure.
What is the top speed for an avalanche?
230 mph
What are the three outcomes of transitional slides?
1) They remain basically coherent.
2) They may deform and disintegrate.
3) They may spread laterally when the underlying material fails and flows.q
How do flows behave and what are some different types of them?
They move like fluids, names for them are Loess flow, earthflow, mudflow, debris avalanche, lahars.
In what ways do avalanches move?
Creep, fall, slide and flow
How do avalanches occur?
From triggers such as earthquakes or people, accumulation high on the slopes loads the head and sets the stage for failure.
What is the top speed for an avalanche?
230 mph
What is subsidence?
The ground moves down and either sags gently or drops catastrophically as voids.
What material often involved with subsidence causes the collagpse of roads built on top?
Limestone
What in rock helps support the weight of overlying rock?
Fluids
What happens when water or oil are squeezed or pumped out of pores in rock or grains?
The pore pressure casues the grains to move together and they are compacted.