Transcript CE 4780 Hurricane Engineering II: Earth Retaining

CE 4745:
Landslides, Slope Stability
and Earth Retaining
Structures
Dante Fratta
Spring 2004
Introduction
• Landslides
• Slope Stability
• Need for Earth Retaining Structures and
Flooding Protection
• Discussion of Factors Influencing Design
• References and Bibliography
Landslides
URL:
landslides.usgs.gov
Landslides
URL:
landslides.usgs.gov
The Mamayes, Puerto Rico, landslide, 1985. This landslide destroyed 120 houses and killed
at least 129 people, the greatest number of casualties from any single landslide in North
America. The catastrophic block slide was triggered by a tropical storm that produced
extremely heavy rainfall. Contributing factors could also have included sewage directly
discharged into the ground in the densely populated area, and a leaking water pipe at the top
of the landslide.
Landslides
URL:
landslides.usgs.gov
La Conchita, California-a small seaside community along Highway 101 south of Santa
Barbara. This landslide and debris flow occurred in the spring of 1995. Many people were
evacuated because of the slide and the houses nearest the slide were completely destroyed.
Fortunately, no one was killed or injured.
Landslides
URL:
landslides.usgs.gov
Fire-related debris flows from Storm King Mountain, Colorado. Debris flows blocked Interstate70 during Labor Day weekend, 1994. A very hot and fast-moving wildfire in July of that year on
the slopes of Storm King Mountain denuded the slopes of vegetation. An intense rainstorm
generated debris flows from material on the burned hillslopes and in the channels between
hills. Interstate traffic was disrupted for a day and caused serious delays for emergency
vehicles and hospital access, due to the fact that Interstate-70 is the only access route through
this part of the Rockies. The Interstate-70 corridor through the Rocky Mountains experiences
numerous problems from landslides, debris flows, and rockfalls.
Landslides
UL:
landslides.usgs.gov
The 1983 Thistle landslide at Thistle, Utah-This landslide began moving in the spring of 1983 in
response to groundwater buildup from heavy rains the previous September and the melting of
deep snowpack for the winter of 1982-83. Within a few weeks the landslide dammed the
Spanish Fork River, obliterating U.S. Highway 6 and the main line of the Denver and Rio
Grande Western Railroad. The town of Thistle was inundated under the floodwaters rising
behind the landslide dam. Total costs (direct and indirect) incurred by this landslide exceeded
$400 million, the most costly single landslide event in U.S. history.
Landslides
UL:
landslides.usgs.gov
The Madison Canyon landslide near Yellowstone Park. This landslide occurred after the
Hebgen lake earthquake (Richter Scale Magnitude = 7.5) in Montana, in 1959. The earthquake
caused a great slide of rock, soil, and trees to fall from the steep south wall of the Madison
River Canyon. Twenty-eight people camping in the area were killed as they were overtaken by
this 21 million cubic meter mass. The landslide formed a barrier that completely blocked the
gorge and the flow of the Madison River, and created a lake.
Landslides
URL:
landslides.usgs.gov
Rock and snow avalanche, Mount Huascaran, Peru. In 1970, an earthquake-induced rock and
snow avalanche buried two towns. The death toll from the Debris Avalanche was 18,000 (total
fatalities from the earthquake and the debris flow was 66,000). The avalanche started as a
sliding mass of glacial ice and rock about 3,000 feet wide and one mile long. The avalanche
swept about 11 miles to the village of Yungay at an average speed of more that 100 miles an
hour. The fast-moving mass picked up glacial deposits and by the time it reached Yungay, it is
estimated to have consisted of about 80 million cubic yards of water, mud, and rocks.
Landslides
URL:
landslides.usgs.gov
Melting snow and ice on the north flank of Washington's Mount St. Helens, triggered this lahar
(an Indonesian term for a "volcanic debris flow"), which rapidly traveled down the flanks of the
mountain with the North Fork of the Toutle River. The melting snow and Ice resulted from the
1982 eruption of Mount St. Helens
Landslides
URL:
landslides.usgs.gov
Sinkhole at Winter Park Florida-Sinkholes (1981): Subsidence occurs when carbonate layers
that lie below the surface dissolve. When the weight of the overlying ground becomes too
great, or the dissolved area too large, the surface collapses into the void. These features
occur in what is known as karst topography which is common in FL, KY, MO, PA, and TN
Landslides
The Problem
• Landslides constitute a major geologic hazard because
they are widespread, occurring in all 50 states, and
cause $1-2 billion in damages and more than 25
fatalities on average each year.
• Landslides pose serious threats to highways, lifelines,
and structures that support fisheries, tourism, timber
harvesting, mining, and energy production as well as
general transportation.
Landslides
The Problem (cont.)
• Landslides commonly occur with other major natural
disasters such as earthquakes and floods that
exacerbate relief and reconstruction efforts and
expanded development and other land use has
increased the incidence of landslide disasters.
• Source: The National Landslide Hazards Program (2002)
Landslides
The Problem (cont.)
(Nelson 2004)
Landslides
Triggering Mechanisms
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Intense Rain-Fall
Water-Level Change
Ground Water Flow
Rapid Snowmelt
Volcanic Eruption
Earthquake Shaking
Human activity
Landslides
• Landslide: General term for any perceptible down slope
movement of rock or soil
– Can include bedrock, soil, or a mixture of these
– Classified according to the mechanisms responsible for the
movement and the velocity of the movement
• Slope Failures - sudden failure of the slope resulting in
transport of debris down hill by slumping, rolling, falling,
or sliding
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Slumps
Falls
Slides
Sediment Flows - debris flows down hill mixed with water or air
(Nelson 2004)
Landslides
• Types and Processes
(Canada Natural Resources 2002)
Landslides
• Landslides Types
– Fall: is the detachment
of soil or rock from
steep slopes along the
surface. Little or no
shear displacement
(e.g. loess).
– Topple: is the forward
rotation of soil or rock
mass about a point.
(Turner and Schuster 1996)
Landslides
• Landslides Types
–Slide: is the downslope displacement of soil or rock
masses. It includes: rotational, translational, and
debris slide
(Turner and Schuster 1996)
Landslides
• Landslides Types
– Flow: continuous
movement of soil
masses where shear
surfaces are short
lived.
– Spread: is the sudden
movement of water
bearing rock masses
(Turner and Schuster 1996)
Slope Stability
• Slope Stability Analysis (Abramson et al. 2002)
– understand the development and shape of natural
slopes
– determine the short-term and long term stability
conditions
– evaluate the possibility of failure of natural or
engineering slides
– analyze and understand failure mechanisms
– enable the retrofit of failed slopes
– understand the effect of seismic loading on slope and
embankments
Slope Stability
Effect of Water on Soils
• Dry sand grains will form a pile. The slope angle is determined by
the angle of repose (i.e., the steepest angle at which a pile of
unconsolidated grains remains stable - controlled by the frictional
contact between the grains. It usually lies between about 30 and 37
degrees.
Dry sand
Angle of
repose
Grain-to-grain frictional contact
(Nelson 2004)
Slope Stability
Effect of Water on Soils
• Slightly wet soil materials exhibit a very high angle of repose
because surface tension between the water and the grains tends to
hold the grains in place.
Wet sand
Angle of
repose
Surface tension thin film
(Nelson 2004)
Slope Stability
Effect of Water on Soils
• When the material becomes saturated, the strength may reduced to
a very small values and it may tends to flow… water (between the
grains) eliminates grain to grain frictional contact.
Fully saturated
sand
Angle of
repose
Water surrounds the grain and
prevent grain-to-grain contact
(Nelson 2004)
Slope Stability
Slope Stability Failure
(after Duncan)
Slope Stability
Slope Stability Failure
(after Duncan)
Need for Earth Retaining Structures
• Each year flooding causes more property damage in
the United States than any other natural disaster.
• Annually, flood damages average over $3 billion (Lilli
damages expected to raise to $ 600 million Levitan).
• In 1985 the estimated flood damage was $6 billion
and affected over 250,000 structures.
Need for Earth Retaining Structures
• Average flood damage for a home is approximately
$20,000 per flood and is much higher for industrial
buildings.
• Flooding is not only expensive to the homeowner
and the taxpayer, but also causes despair and worry
for its victims.
• Effective flood protection and preventive measures
can significantly reduce the expense and trauma
caused by flooding
• Source: National Flood Proofing Committee (2002).
Need for Earth Retaining Structures
The Landslide Problem
Slope failure near McClure Pass, Colorado (The
National Landslide Hazards Program 2002)
Flooding Protection
• Incomplete List…
– Retaining walls
– Sheet piles
– Dams and reservoirs
– Levees
– Embankments
– Other: diversion channels, retaining ponds,
etc…
Flooding Protection
Retaining walls and sheet piles (Bowles 1988)
• Retaining walls are structures used to retained soils or other
granular materials.
• Materials: masonry, concrete, wood, metal sheeting, reinforce
earth, etc.
• The analysis and design of retaining walls is governed by the
stiffness of the wall: rigid or flexible.
Sheet pile
Drainage pipe
(Cheifetz 2002)
Flooding Protection
Dams and reservoirs (US Society on Dams 2002)
• A dam is built to control water. Dams are made from earth, rocks
or concrete.
• Dams are usually constructed on rivers to store water in a
reservoir.
• Dams help people have water to drink and provide water for
industry, irrigation, fishing and recreation, hydroelectric power
production, navigation in rivers, etc. Dams also serve people by
reducing or preventing floods.
(from McCarthy
1998)
Flooding Protection
Levees (The Academy of Science of Saint Louis 2002):
• Levees are low ridges or earthen embankments made of
silt, sand or clay, built along a stream of water.
• They help in the prevention of flooding of the adjacent
land.
• Levees can be either naturally occurring or man-made.
• Man-made levees consist of an impermeable core
surrounded by an earthen material, with some type of
protection to minimize erosion.
Flooding Protection
Levees (The Academy of Science of Saint Louis 2002):
• Dimensions of a levee are typically 2.5 m across the top,
the height 0.30 m above the level of a predicted flood
having once in 50-year frequency, the slope on the river
side being three up per one across and the slope on land
side five feet up per one foot across.
• There are federal standards for dimensions depending
on the local material available, anticipated force of the
river and the amount of development in the area.
Flooding Protection
Levees (McMillan, J. - The
Advocate 2002)
“Deep fissures on the batture - land
between the levee and the
Mississippi River - reveal the
ground is again sinking at the spot
where the levee collapsed in 1983.”
Discussion of Factors Influencing
Design
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Social Requirements
Engineering Requirements
Economical Constrains
Environmental Actions
– Water level
– Rain: intensity and duration
– Wind action
• Soils – Material Properties
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Grain size distribution
Degree of saturation
Void ratio
Strength
References and Bibliography
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Abramson, L. W., Lee, T. S., Sharma, S., and Boyce, G. M. (2002). Slope
Stability and Stabilization Methods. Wiley and Sons.
Bowles, J. E. (1988). Foundation Analysis and Design. McGraw-Hill.
Canada Natural Resources (2002). Geoscape Calgary. URL:
http://www.nrcan.gc.ca/gsc/calgary/geoscape/index_e.html
Cheifetz, D. (2002). Slope Stability. URL: http://soilslab.cfr.washington.edu/
ESC311-507/2001/FinalProjects/DAVID-CHEIFETZ/
Eckel, E. B. (1958). Landslides and Engineering Practice. Highway
Research Board. Special Report 29. NAS-NRC Publication 544.
Washington DC. 232 pages.
The National Landslide Hazards Program (2002). URL:
http://landslides.usgs.gov/ html_files/landslides/program.html
Louisiana Floods (2002). URL: http://www.louisianafloods.org/
McCarthy, D. (1998). Essential of Soil Mechanics and Foundation. PrenticeHall.
References and Bibliography
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McMillan, J. (2002). “Fissures near old site worry corps officials”. The
Advocate Online. URL: http://www.theadvocate.com
Nelson, S. (2004) . Mass-Wasting and Mass-Wasting Processes. URL:
http://www.tulane.edu/~sanelson/geol204/masswastproc.htm
National Flood Proofing Committee (2002). URL: http://www.usace.army.
mil/inet/functions/cw/cecwp/NFPC/nfpc.htm.
The Academy of Science of Saint Louis (2002). URL: http://www.jracademy.
com/~mlechner/archive1999/link-levee.html.
Turner, A. K. and Schuster, R. L., Ed. (1996). Landslides. Investigation and
Mitigation. Special Report 247. Transportation Research Board. National
Research Council. Washington DC. 673 pages.
US Geological Survey (2004). Landslide Hazards. URL:
http://landslides.usgs.gov/