Deck 8: Landslides and Other Downslope Movements

Question 1

What is a daylighted surface or layer?

A) a weak layer, sloping down toward a road cut or hillside at a somewhat gentler slope than the hillside
B) a part of the bedrock that is exposed at the surface
C) a layer that becomes exposed by excavation of a road cut
D) a layer that becomes exposed at the surface by artificial removal of soil over it
E) a layer exposed at the surface by landsliding

Answer 1

A

Question 2

One way in which water CANNOT be removed from a wet slope that may slide is to:

A) plant trees and shrubs to increase evapotranspiration.
B) insert perforated pipes into the slope to help drain it.
C) dig a trench across a slope and fill it with loose, coarse rock to permit drainage.
D) pump water out from a well.
E) place a load on the slope to squeeze water out of it.

Answer 2

E

Question 3

What kind of material is most likely to fall in a rotational slide?

A) homogeneous, cohesive materials
B) rounded sand grains in the slope
C) elongated boulders with smoothly rounded sides
D) loose, dry soils
E) talus slopes

Answer 3

A

Question 4

Which of the following states is NOT susceptible to landslides?

A) Florida
B) Colorado
C) Montana
D) Pennsylvania
E) Texas

Question 5

Why does earthquake shaking of water-saturated sand often lead to ground settling?

A) The shaking of sand leads to closer packing of the grains.
B) The shaking wears off the edges of the grains making them smaller.
C) The shaking makes the grains settle in the water.
D) It doesn't. Settling only occurs if you pump water out of the ground.
E) Shaking rearranges the atoms in the grains, allowing them to fit closer together.

Question 6

The angle of repose for dry sand is __________ degrees.

A) 5 to 15
B) 25 to 35
C) 45 to 55
D) 35 to 45
E) 15 to 25

Question 7

Why does raising the groundwater level often lead to slope failure?

A) It lubricates the ground, making it slide easier.
B) It creates a layer of water that the slope slides on.
C) It increases the water pressure in the pore spaces between the grains, pushing them farther apart.
D) When the ground freezes, the water turns to ice, making it slide easily.
E) The water seeps out of the ground, and the slope above slides on it.

Question 8

Why does the top of a rotational slide tilt back into the slope?

A) As the slide moves away from its head scarp, material slides back into the gap.
B) The slide mass rotates on a circular curving surface, so everything on it rotates backward.
C) The inertial pull of the fast-moving slide leaves a gap behind at the top.
D) Since the slide mass pulls away from the head scarp, it leaves a gap that tilts backward.
E) Since the top of the mass is pulled forward, the bottom tilts back, just as you would if you slipped on ice.

Question 9

Which slope material is most likely to move as a translational slide?

A) homogeneous, cohesive materials
B) a raised terrace of old beach sediments
C) moist soil 300 meters thick
D) 3 meter thick soil over bedrock
E) deeply weathered granite rich in clays

Question 10

What major factor does NOT control the maximum height of water downstream from failure of a dam?

A) water height behind the dam
B) volume of water
C) distance downstream from the dam
D) width of the valley
E) length of the reservoir upstream of the dam

Question 11

What is "cohesion" as applied to slope failure?

A) the condition of a slope that has not yet begun to slide
B) loose grains in a slope that are angular rather than rounded so they don't slip past one another easily
C) the holding together of otherwise loose grains on a slope, often by a little moisture
D) grains in a rock that have interlocked as a result of metamorphism
E) grains in a granite or similar rock that don't separate easily

Question 12

What CANNOT be used to recognize the action of soil creep?

A) tree trunks that bend out from a slope before curving up
B) fences that lean downslope
C) walls that lean downslope
D) fragments of rocks that clearly came from farther upslope
E) bedrock layers that curve downslope as they approach the surface

Question 13

The main factors that affect the chance that a slope will fail in a landslide do NOT include:

A) slope angle or steepness.
B) strength of slope material.
C) amount of water.
D) age of the slope.
E) internal surfaces subparallel to the slope.

Question 14

Which of the following would NOT cause the height of water in the ground to rise,thus increasing the danger of sliding?

A) leaking pipes
B) cracked swimming pools
C) septic drain fields
D) planting trees
E) filling a reservoir behind a dam

Question 15

Why do highway departments sometimes pile huge boulders near the base of a sloping road cut?

A) to prevent gullying of the sloping road cut
B) to keep vegetation from growing on the sloping road cut
C) to prevent water from getting into the slope
D) to prevent slumping of the road cut by loading the toe of the potential slump
E) to prevent damage to the road cut from collisions with erratic drivers

Question 16

Why does swelling clay swell?

A) Landsliding pushes the edges of the grains, so they buckle and thicken.
B) Freezing causes the water in them to swell.
C) Water gets into the clay layers, spreading them apart.
D) Drying the clay makes it swell like cooking a cake.
E) Deformation of grains during sliding interleaves clay flakes, making them thicker.

Question 17

Old landslides are NOT normally reactivated by:

A) adding water.
B) earthquakes.
C) steepening the slope by removing material at the lower part of the slope.
D) steepening the slope by adding material at the upper part of the slope.
E) piling heavy rocks on the lower part of the slope.

Question 18

What types of internal surfaces are LEAST prone to sliding?

A) planes sloping at somewhat steeper angles than the slope
B) planes sloping at somewhat gentler angles than the slope
C) old landslide slip surfaces
D) daylighted surfaces
E) planes cemented by smectite

Question 19

Where are quick clays most common?

A) Northern coasts-Alaska, Canada, northern Europe
B) Tropical areas-Central America, Brazil, Africa
C) U.S. Gulf Coast-Texas through Florida
D) Coastal cliffs of California
E) Rocky Mountains of Colorado

Question 20

For a rockfall,what two factors lead to a greater distance of travel of the moving debris?

A) more water in the mass and release promoted by freezing
B) greater height of fall and a block that is not too angular
C) greater size of the falling mass and smaller particles
D) greater height of fall of the mass and greater volume of the falling mass
E) greater height of fall and higher clay content

Question 21

What three methods can be used to minimize damage from rockfalls?

Question 22

The disastrous Vaiont landslide in Italy involved what combination of circumstances?

Question 23

What material is subject to liquefaction?

Question 24

What can be done to stabilize a steep,dangerous rock cliff or road cut to keep it from collapsing onto a highway or railroad track?

Question 25

Describe what occurred during the Frank Slide in 1903.What type of downslope movement occurred here? Why do you think the rock material was able to travel so far?

Question 26

What types of internal surfaces are most prone to sliding?

Question 27

List three ways in which human activity can increase the danger of landsliding.

Question 28

What would make a pile of rounded sand grains collapse to be almost flat?

Question 29

What is the difference between a slump and a translational slide?

Question 30

Why do some slopes fail in a rotational slump rather than a translational slide?

Question 31

What orientation of rock layers or fractures in a hillside or road cut is particularly dangerous? Why?

Question 32

What is the arrangement of clay grains after their rearrangement during quick-clay movement?

Question 33

What conditions make smectite clay extremely weak?

Question 34

How does evapotranspiration work? List the main aspects.

Question 35

For a rockfall,what two factors lead to a greater distance of travel of the moving debris?