failure surface melissa beukeboom @. gravity is the force that pulls everything toward the centre of...
Post on 14-Dec-2015
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Gravity is the force that pulls everything toward the centre of the Earth
Friction between soil particles must RESIST the pull of gravity
2. Erosion
3. Water content in soil
4. Disturbances like: Earthquakes
Volcanic eruptions
Machinery, traffic, mining
1. Type of sediment
ROCK PARTICLES
a.k.a. SEDIMENTS
WATER AIR ORGANIC MATTER
Let’s take a
closer look!1. Type of Rock Particles
(a.k.a. Sediment)
Rocks are weathered (broken down) by water, wind, and ice into smaller and smaller pieces called
Main types of SEDIMENTS:gravelsandsiltclay
SEDIMENTS
1. Type of Rock Particles (a.k.a. Sediment)
Gravel and sand grains are very angular in shape. Their sharp edges hold on to each other, increasing FRICTION and fighting GRAVITY.
1. Type of sediment (continued)
Clay particles are flat and fit together very tightly.
This prevents water from moving between clay particles easily.
Water pressure can build up in slopes made of clay.
QUICK CLAYS IN ONTARIO
We are here!
Ottawa & QuebecLEDA CLAY OR CHAMPLAIN SEA CLAY
Northern Ontario & Quebec
TYRRELL SEA CLAY
Do we have quick clays in Ontario?
YES!
1. Type of sediment (continued)
The card house structure makes quick clay very stable….
Until the structure is disturbed!!
2. Erosion
When a slope is over-steepened, it becomes unstable
Rivers erode the base of slopes and make them too steep…making it unstable
RIVERRIVERRIVERRIVERRIVER RIVER
3. Water Content
Too much water added to soil, pushes the sediment particles apart.
The particles lose contact with each other…therefore they lose FRICTION!
So GRAVITY wins!
4. Disturbances
Disturbances also push particles apart, causing them to lose contact with each other
They lose FRICTION, so….
So GRAVITY wins!
Let’s re-cap…Landslides occur when the land is unstable…allowing
GRAVITY to win!
Instability depends on: The type of sediment
Water content in the soil
Erosion over-steepening the slope
A major disturbance
When a landslide occurs…
It can be fast
It can look like “the wave” or falling dominos
The “domino effect”
To conclude…here is a bit humour…
or slow
Imagine the people are sediment particles
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