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Definition
| The large-scale transfer of material down slope under the pull of gravity. |
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Definition
| Power behind, Rainfalls, water flows, ice glides, wind blows, and wave breaks. |
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Definition
The slow, gradual, more or less continuous movement of ice, soil, and faults under stress.
- slowest but most common form of slope failure. |
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Definition
| The tendency of a body to remain at rest until an external force is applied. |
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Definition
| Resistance to motion of a body that keeps it from moving over another body. |
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Term
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Definition
- Soil has high percentage of void space or porosity. When water freezes, it expands in volume by 9%, swelling the soil volume and lifting the ground surface upward.
- When soil rich in expandable materials, such as some types of clay minerals, is wetted, it absorbs water and expands.
- Heating by the Sun causes an increase in volume. Soil expands perpendicular to the ground surface. |
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Term
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Definition
- Thawing of soil
- Drying
- Cooling |
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Term
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Definition
Mass whose center of gravity has moved downward and outward. It's caused by,
- Adding mass on the top
- Steepening slope
- Removing support from the bottom |
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Term
| Internal causes of slope failure |
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Definition
1) Inherently weak materials
2) Water in different roles
3) Decreasing cohesion
4) adverse geologic structures |
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Term
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Definition
| The decomposition of rocks under attach of base- or acid-laden waters. |
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Term
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Definition
| Clay increases or decreases in strength, and expands and contracts depending on the amount of water. Conditions change by month and year, weakening clay and increasing slope failure. |
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Term
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Definition
| Water is absorbed between interlayer sheets, causing grains to spread resulting in expansion. |
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Term
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Definition
| Found in US, it usually loses all its shear strength after being disturbed. |
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Term
Weight
(Water's effect on Earth's Materials) |
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Definition
| Because water is heavier than air, when the spaces between particles fills with water, it causes displacement of the materials. |
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Term
Absorption and Adsorption
(Water's effect on Earth's Materials) |
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Definition
| Because water is a bipolar molecule and it's outside hydrogen molecules are positively charged, it binds well with negatively charged clay molecules. |
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Term
Dissolve Cement
(Water's effect on Earth's Materials) |
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Definition
| Flowing water can break the bonds between rocks and decrease slopes strength. |
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Term
Piping
(Water's effect on Earth's Materials) |
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Definition
| Physically erode loose material, leaving caverns and compromises the strength of the hill. |
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Term
Pore-Water Pressure
(Water's effect on Earth's Materials) |
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Definition
| Because water is nearly incompressible, pressure is stored in water and the buildup of pressure lifts sediments, and gravity causes the movement of material. |
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Term
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Definition
| Super saturated grains of sand are supported by pressurized water, with no ability to carry a load. |
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Term
Water Table
(Water's effect on Earth's Materials) |
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Definition
| Water saturates and fills open spaces. Rising amounts of groundwater cause mass movements. |
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Term
Dam Disaster in Vaiont, Italy
1963 |
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Definition
Dam failure that caused 3,000 deaths.
1.1 mile long and 1 mile wide, filling reservoir 500 feet above capacity. Wall of water 240 ft high. Displacement of air shattered windows and lifted roofs off houses.
1) Sedimentary rocks layers folded into a trough-like configuration.
2) Fractures split the rocks apart and into a "V" shape.
3) Previous sliding left old slide surfaces on weak clays.
4) Some rocks layers contained thin streams of weak clays.
5) Limestone caused caverns
6) Water saturated rocks caused elevated pore-water pressures. |
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Term
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Definition
| -Rocks that are burred thousands of feet below the surface, they are compacted into smaller and denser volume rocks. When they are exposed to air, they relax and expand. The expansion causes and increase in porosity and fractures, reducing the strength of the rock. |
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Term
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Definition
| Weaknesses that are reused over time. A smooth layer is left after a materials break loose, and become slippery when wet. These slide surfaces are easily reactivated. |
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Term
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Definition
| Rock layers that dip at a lower angle than the slope of a hill, which is cause for mass movement due to their lack of support at their ends. |
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Term
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Definition
Rocks have weaknesses that set them up for failure.
1) Rocks aren't cemented together.
2) A clay layer may provide a basal slip surface.
3) Soft rock layers may slide off strong materials.
4) Joints split and separate rock,
5) Ancient fault may act as a slide surface. |
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Term
| Triggers of Mass Movements |
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Definition
Most failures have several complex causes.
Common Causes
- Heavy rains
- Earthquakes
- Thawing of frozen ground
- Construction projects by humas. |
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Term
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Definition
Slow moving masses cause tremendous amounts of destruction and property damage.
Rapidly moving masses not only destroy, they kill. |
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Term
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Definition
Downward (falling from a topographically high place or subsiding via collapse of the surface)
Downward and outward (sliding down and out on top of an underlying failure surface and flowing like a viscous liquid) |
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Term
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Definition
-Elevated rock masses separate along joints, rock layers, or other weaknesses.
EXAMPLE: Yosemite National Park
Triggers:
- Heavy Rainfall
- Frost Wedging
- Earthquakes |
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Term
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Definition
Movements about one or more failure surfaces.
Rotational Slides- downward and outward on top of curved surfaces.
Slump- head moves downward and rotates back. (move slowly) |
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Term
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Definition
Masses move down and out by sliding on surfaces of weakness, such as faults, joints, a clay rich layer, soft rocks slipping off hard rocks, and hard rocks being spread apart by movements within underlying soft rocks.
- They may remain basically coherent as block slides
- The sliding mass may deform and disintegrate to form a debris slide
- Lateral spreading may occur where underlying material fails and flows. |
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Term
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Definition
| Mass Movements that behave like fluids with different viscosity, water content, and velocities. |
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Term
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Definition
| Sturzstroms- fall stream. Massive rock falls that convert into highly fluidized, rapidly moving debris flows that travel far and kill in great numbers. |
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Term
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Definition
Snowfall yield to the pull of gravity and fail. Avalanches also creep, fall, slide, and flow.
- Commonly initiate on steep slopes when snowfall reaches 1.5-5 ft deep.
- Loose Powder Avalanches typically fails at a source point, and because the snowflakes have less cohesion, they pack well.
- Slab Avalanches involve the breaking free of slabs of cohesive snow. The translational slides eventually break up and turn into flows. |
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Term
| Controlling Earth/Snow Flows |
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Definition
- Steering the flow away from buildings and people by digging channels or building walls.
- Removing rock and decreasing the slope angle
- Using fence to hold rocks in place |
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Term
| How to Prevent a landslide |
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Definition
1) Unload the head
2) Strengthen the body
3) Support the toe |
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Term
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Definition
| New land formed where rivers drop their loads of sand and mid at the shoreline while building out into seas or lakes. |
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