1. Subsidence Natural Man induced

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

3. Earth 514 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 being monitored.

14. ”Sink hole”

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

16. Karst landscape 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

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