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Subsidence

Subsidence . Natural Man induced. Natural subsidence. Plate tectonics – regional changes in land and water . Earth 514 million years ago . Earth 458 million years ago. Earth 390 million years ago. Earth 3 06 million years ago. Earth 237 million years ago.

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Subsidence

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  1. Subsidence Natural Man induced

  2. Natural subsidence • Plate tectonics – regional changes in land and water

  3. Earth514 million years ago

  4. Earth 458 million years ago

  5. Earth 390 million years ago

  6. Earth 306 million years ago

  7. Earth 237 million years ago

  8. Earth 94 million years ago

  9. Earth 14 million years ago

  10. Natural subsidence • Plate tectonics – regional changes in land and water • Karst – chemical weathering of soluble rocks

  11. Karst Collapse of solution cavities in soluble rocks

  12. Sink hole Collapse of solution cavities in soluble rocks

  13. 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 beingmonitored.

  14. ”Sinkhole”

  15. Karstlandscape water and carbon dioxide mix to form carbonic acid which disolves the limestone

  16. Karstlandscape water and carbon dioxide mix to form carbonic acid which disolves the limestone

  17. formation of karsts • with time the fractures and joint widen

  18. formation of karsts underground rivers and large caves form

  19. formation of karsts • When the weight of the overlying ground exceeds the strength of the rock then collapse occurs

  20. Formed by the catastrophic collapse of an underlying cave, the Lost River Cave Valley

  21. Man induced subsidence • Mining - • Water • Oil • Gas • Rocks and minerals • Loading

  22. Man induced subsidence • Mining - • Compaction • Collapse • Faults

  23. Man induced subsidence • Mining • Compaction • Collapse • Faults

  24. Extraction of liquids or gas • compaction • collapse • faults

  25. Man induced subsidence • Mining - • Compaction • Collapse • Faults

  26. Man induced subsidence • Mining - • Compaction • Collapse • Faults

  27. Man induced subsidence • Mining - • Compaction • Collapse • Faults

  28. Man induced subsidence • Mining - • Oil • Gas

  29. Man induced subsidence • Mining - • Oil • Gas

  30. Man induced subsidence • Mining - • Oil • Gas • Mitigation – pump in water to hold up the overburden

  31. Man induced subsidence • Mining - • Rocks and minerals

  32. mine > collapse

  33. mine > collapse

  34. mine > collapse

  35. Man induced subsidence • Mining - • Rocks and minerals

  36. Man induced subsidence • Mining - • Rocks and minerals

  37. Risk maps – subsidence due to underground oil shale mine in Estonia

  38. Loading • Compaction • Volume change • Subsidence

  39. Liquifaction – • When shaken the strength of the soil is lost

  40. Shaking • earthquake • vibrations from • roads • railroads

  41. Shaking • liquefaction

  42. Expansive soils • expansive clays • Bentonite • Montmorilonite

  43. Expansive soils • Expansive clays • Bentonite • Montmorilonite

  44. Management • Accept – do nothing • Avoid – plan away • Defend – build to protect against

  45. 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

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