Slopes

Question 1

What causes slope failure

Answer 1

when natural conditions and/or human-induced conditions caused a change in the forces that act at the slope area

This type of movement is known as Slope Failures or Landslides or just Slides

Question 2

What natural conditions can cause slope failure?

Answer 2

 Earthquake
 Erosion
 A general slope weakening because of the cracks’ development
 A change in the elevation of ground water table

Question 3

What human induced conditions can cause slope failure?

Answer 3

 Increased loading on a slope or near its crest
 Removal of earth below the toe of a slope
 Removal of material from a slope so as to make it
steeper

Question 4

Define: Cut slopes

Answer 4

slopes that are those made by an excavation. They expose natural ground that was once buried

Question 5

Define: Fill Slopes

Answer 5

slopes made by placing fill

Question 6

Define: Natural Slopes

Answer 6

slopes that are part of the natural topography

Question 7

Define: Slope Ratio

Answer 7

Describes the steepness of a slope, always expressed as horizontal to vertical H:V

Question 8

Define: top of slope/toe of slope

Answer 8

the point where the slope intersects flat ground

Question 9

Define: slope face

Answer 9

the ground surface between the top of slope and toe of slope

Question 10

Define: slope height

Answer 10

H, the difference in elevation between the top of slope and toe of slope (measured vertically, not diagonally along the face of the slope)

Question 11

Define: terrace

Answer 11

a narrow area created in cut and fill slopes to accommodate surface drainage facilities

Question 12

What is a rotational slide?

Answer 12

type of slope movement, a slide that moves along curved surfaces known as slip or failure surfaces

Question 13

What is a translational slide?

Answer 13

type of slope movement, a slide along two planar surfaces

Question 14

What is a block/wedge failure?

Answer 14

type of slope movement, refers to the displacement
of an intact mass of soil
because of the action of
an adjacent zone of earth

Question 15

What is a “flow” type of slope movement?

Answer 15

-involves lateral down slope movement of soil
-when soil behaves like a viscous fluid, (although actual consistency may vary)

Flows differ from slides. They are
not well-defined blocks moving along shear surface.

Question 16

What is a lahar?

Answer 16

a type of slope movement, a type of mudflow or debris flow composed of slurry, rocky debris, and water

-material flows down from a volcano, typically along a river valley

Question 17

what is the failure/slip surface?

Answer 17

“failure surface” refers to the theoretical or actual surface within a soil or rock mass along which failure or instability occurs.

Question 18

what is Limit Equilibrium Analysis (LEA)?

Answer 18

the quantitive analysis of
slides or potential slides

evaluate the slope as if it were about
to fail and determine the resulting shear
stress along the failure surface

Failure is indicated when moments causing motion exceed those resisting motion

Question 19

What are the two types of rotational slides?

Answer 19

Spoon shaped

Cylindrical Shaped

Question 20

safety factor =

Answer 20

Against sliding:
Safety factor=shear strength available/shear strength requried

With respect to LEA Method/Concepts

Safety Factor = moment resisting sliding/moment causing sliding

Question 21

What is an acceptable safety factor (FS)?

Answer 21

For intact homogeneous soils, when the strength
parameters have been chosen on the basis of good
laboratory tests and careful estimate of pore
pressure has been made, a safety factor of at least