Subsidence

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Subsidence

• Natural
• Man induced

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Natural subsidence

• Plate tectonics regional changes in land and
  water

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Earth 514 million years ago
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Earth 458 million years ago
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Earth 390 million years ago
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Earth 306 million years ago
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Earth 237 million years ago
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Earth 94 million years ago
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Earth 14 million years ago
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Natural subsidence

• Plate tectonics regional changes in land and
  water
• Karst chemical weathering of soluble rocks

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Karst

• Collapse of solution cavities in soluble rocks

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Sink hole

• Collapse of solution cavities in soluble rocks

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Sink hole

• A large subsidence occurred in Waihi early in the
  morning (about midnight) on the 13 December. The
  large 50m diameter sinkhole that developed
  destroyed a house, a caravan, several cars and
  smaller buildings.  Another house was undermined
  and a third is perched on the edge.  The road has
  collapsed and radial cracking has apeared around
  the feature.  Movement is being monitored.

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Sink hole
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Karstlandscape
water and carbon dioxide mix to form carbonic
acid which disolves the limestone
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Karst landscape
water and carbon dioxide mix to form carbonic
acid which disolves the limestone
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formation of karsts

• with time the fractures and joint widen

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formation of karsts

• underground rivers and large caves form

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formation of karsts

• When the weight of the overlying ground exceeds
  the strength of the rock then collapse occurs

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Formed by the catastrophic collapse of an
underlying cave, the Lost River Cave Valley
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Man induced subsidence

• Mining -
• Water
• Oil
• Gas
• Rocks and minerals
• Loading

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Man induced subsidence

• Mining -
• Compaction
• Collapse
• Faults

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Man induced subsidence

• Mining
• Compaction
• Collapse
• Faults

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Extraction of liquids or gas

• compaction
• collapse
• faults

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Man induced subsidence

• Mining -
• Compaction
• Collapse
• Faults

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Man induced subsidence

• Mining -
• Compaction
• Collapse
• Faults

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Man induced subsidence

• Mining -
• Compaction
• Collapse
• Faults

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Man induced subsidence

• Mining -
• Oil
• Gas

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Man induced subsidence

• Mining -
• Oil
• Gas

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Man induced subsidence

• Mining -
• Oil
• Gas
• Mitigation pump in water to hold up the
  overburden

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Man induced subsidence

• Mining -
• Rocks and minerals

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mine gt collapse
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mine gt collapse
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mine gt collapse
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Man induced subsidence

• Mining -
• Rocks and minerals

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Man induced subsidence

• Mining -
• Rocks and minerals

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Risk maps subsidence due to underground oil
shale mine in Estonia
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Loading

• Compaction
• Volume change
• Subsidence

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Liquifaction

• When shaken the strength of the soil is lost

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Shaking

• earthquake
• vibrations from
• roads
• railroads

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Shaking

• liquefaction

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Expansive soils

• expansive clays
• Bentonite
• Montmorilonite

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Expansive soils

• Expansive clays
• Bentonite
• Montmorilonite

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Management

• Accept do nothing
• Avoid plan away
• Defend build to protect against

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Identification of the potential problem

• Risk maps to avoid
• Aid in planning
• Defense
• Natural difficult to defend against
• Plate tectonics
• Karst important to understand the processes
  involved
• Man induced
• Mining supports, adding fluids, backfilling