Read Chapter 4 Mass Wasting (Pages 108-137)
May also read 138-157 Chapter 5 Snow Avalanches
How do we minimize damage from landslides?
1. understand the hazard
2. Assess the risk from the landslide hazard in the are of concern ( the
ph and sh in that region)
e) for a particular slope that you are worries about carry out a SAFETY
FACTOR analysis. This determines the Probability of Failure of that
slope (ph) How safe is the slope?
Safety Factor = (ca + (w x cos~ x tan 0 ) / (w x sin ~) ***** look at
• = resisting force/driving force
• note a is the area of contact between the potential failure
block and the potential failure plane beneath it
Consider the different terms in the safety factor
1. how do we measure them?
2. What are the possible errors that arise in measuring them
3. Which terms are most critical?
4. Is there anything that we are missing in this analysis?
• Safety Factor ** look at picture ~ =
a. = potential failure-plane angle
• the steeper/bigger ~ is, the lower the S.F is
the safety factor (s.f.) is very sensitive to a change in ~ ( angle of
potential failure plane) ie. A small change in ~ makes a big change in
In rocks, potential failure planes are planes of weakness (also knows
These planes of weakness include
• A) sedimentary bedding planes
• B) faults
• C) joints
o Cracks in rocks where the blocks of rock on either side
of the crack have not moved with respect to each other
(if the blocks gave moved, it is a fault)
o Joints can form by 1. Release of pressure when buried rocks are
brought to earth’s surface during weathering and