Shocks vibrations and liquefaction Ground vibrations decrease material friction

Shocks vibrations and liquefaction ground vibrations

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Why do mass movements occur? - Shocks, vibrations and liquefaction - Ground vibrations decrease material friction - On an unstable slope, the downslope force takes over - Vibrations are common
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- Motion of heavy machinery or trains - Earthquakes - Vibrations can cause saturated sediments to liquefy - Changes in characteristics can destabilize a slope - Loading - adding weight to the top of a slope - Water - as rain or via humans (lawns, septic systems) - materials - buildings, waste materials, fill - Angle - steepening a slope beyond the angle of repose - River incision - Excavation for buildings and roads - Changes in slope strength - Weathering - creates weaker regolith - Vegetation - stabilize slopes. Removing vegetation: - Greatly slows removal of excess water - Destroys an effective stapling mechanism (roots) - Slope failures common after forest fires destroy vegetation Protecting against mass movement - Landslide potential mapping - Identifies areas of potential risk that may not show signs - Assesses multiple factors: - Slope steepness - Strength of substrate - Degree of water saturation - Orientation of planar features - Bedding - Joints - Foliation - Vegetation cover - Heavy rain potential - Undercutting potential - Earthquake probability Preventing mass movements - Action can reduce mass-movement hazards - Revegetation - adding plants has two positive effects - It removes water by evapotranspiration - Roots help to bind and anchor regolith - Redistributing mass by terracing - Removes some of the mass loading a slope - Catches debris - Engineered structures - Rock staples - rods drilled into rock to hold loose facing - Avalanche sheds - structures that shunt avalanche snow
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- Controlled blasting - surgical removal of dangerous rock
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