3.8. (9/11) LANDSLIDES - hillslope transport Flashcards
what are some characteristics of landslides?
- internally crumbling and deforming
- whole coherent mass moves
- there is a slide plane
what is the slide plane?
- a discreet plane below which there is no more movement
- point of failure
what is the difference between a creep and landslide?
mass moves above a plane at a constant rate whereas in creep the whole soil profile slowly moves downslope (velocity gradient too)
what are the conditions necessary for a material to move?
function of:
- slipperiness of the slide plane (wetness, pore pressure counteracts the weight of material, floats)
- stickiness
- weight
- the steepness of plane
What would the texture of the deposit be as it moved down?
What is the safety factor?
the forces resisting a landslide vs the forces driving it to become a landslide
What is the safety factor formula?
resisting force/driving force = C + σntanФ/τ = (C+ρghcos2α-μtanФ)/ ρghsinαcosα
What does a safety factor of less than one mean?
if the driving force is bigger than resisting = landslide
What does a safety factor of more than one?
if the resisting force is bigger than the driving force = stable
What does a safety factor of one mean?
instability, teetering edge
what are the different forces acting on a moving object?
friction, normal stress, and shear stress
What is W? what is its formula?
weight of the block
densitygravitational accelerationthickness*the angle that it’s at (cosα) on a slope
what is σn? what is its formula?
normal stress: force that holds down object on plane
Wcosα
what is τ? What is its formula?
Shear stress: force pulling an object down a slope
Wsinα
What is C?
cohesion, y- intercept
What is f? what is its formula?
Friction: force holding object back against a slope
Wsinα/Wcosα = tanα
What is μ? What is its formula?
the effective normal stress
ρghmcos2α
What is m?
how saturated the object is (where 1 is the most saturated)
In a shear stress-normal stress graph what is the slope called?
failure envelope or tanФ or how steep the line is
What is tanФ?
angle of internal friction
what is another way to write y = mx + b?
τ = tanФ*σn + C
What is the equation for resisting force?
tanФ*σn + C
What is the equation for the driving force?
τ (tau)
