12. Mass Wasting. Classifications (Definitions, processes and controlling factors) Examples (Appling knowledge of processes) Prevention of Mass Wasting (limiting and eliminating). Definitions Flow, Slide, Fall Controlling Factors Gravity Water Shear strength Examples
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Classifications (Definitions, processes and controlling factors)
Examples (Appling knowledge of processes)
Prevention of Mass Wasting (limiting and eliminating)
Flow, Slide, Fall
Mt. St. Helens
Yosemite Rock fall/slide
Gros Ventre Slide
St. Francis Dam, Calif.
Be able to distinguish a flow from a slide.
How do controlling factors increase or reduce tendency of mass wasting?
How did the controlling factors lead to these events?
How would you use your knowledge of the controlling factors to reduce risk?Terms and Concepts to Learn
Slope and Material Dependent <5 km/hr
Debris or Rock
Very Fast 100 km/hr
FastClassification of Mass Wasting
Type of Movement
i.e., Shear Force
Fs: Shear force
q : Dip of slope
m: coefficient of static friction
i.e., Shear Strength
se: Effective Stress
f : Angle of internal friction
S resisting forces
S Driving Forces
If S.F.>1 then failure occurs
Before RainfallAfter Rainfall
sT: Total Stress
P: Fluid pressure of ground water (or soil water)
se: Effective stress (stress supported by the soil skeleton)
Note: fluid pressure is negative (less than atmospheric) if unsaturated and becomes positive when saturated
S: Shear Strength
L: Langth of potential surface of rupture
R: Moment Arm
W: Weight of Block
X: Length of gravity moment arm
Some solutions include: