Subsidence Natural Man induced. Natural subsidence Plate tectonics – regional changes in land and...
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Transcript of Subsidence Natural Man induced. Natural subsidence Plate tectonics – regional changes in land and...
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 306 million years ago
Earth 237 million years ago
Earth 94 million years ago
Earth 14 million years ago
Natural subsidence
• Plate tectonics – regional changes in land and water
• Karst – chemical weathering of soluble rocks
Karst Collapse of
solution cavities in soluble rocks
Sink hole
Collapse of solution cavities in soluble rocks
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.
”Sink hole”
Karstlandscap
ewater and carbon dioxide mix to form carbonic acid which disolves the limestone
Karst landscape
water and carbon dioxide mix to form carbonic acid which disolves the limestone
formation of karsts
• with time the fractures and joint widen
formation of karsts
underground rivers and large caves form
formation of karsts
• When the weight of the overlying ground exceeds the strength of the rock then collapse occurs
Formed by the catastrophic collapse of an underlying cave, the Lost River Cave Valley
Man induced subsidence
• Mining - – Water– Oil – Gas– Rocks
and minerals
• Loading
Man induced subsidence
• Mining - – Compaction– Collapse– Faults
Man induced subsidence• Mining
– Compaction– Collapse– Faults
Extraction of liquids or gas
• compaction• collapse• faults
Man induced subsidence
• Mining - – Compaction– Collapse– Faults–
Man induced subsidence
• Mining - – Compaction– Collapse – Faults
Man induced subsidence
• Mining - – Compaction– Collapse– Faults
Man induced subsidence
• Mining - – Oil – Gas
Man induced subsidence
• Mining - – Oil – Gas
Man induced subsidence
• Mining - – Oil – Gas
• Mitigation – pump in water to hold up the overburden
Man induced subsidence
• Mining - – Rocks
and minerals
mine > collapse
mine > collapse
mine > collapse
Man induced subsidence
• Mining - – Rocks
and minerals
Man induced subsidence
• Mining - – Rocks
and minerals
Risk maps – subsidence due to underground oil shale mine in
Estonia
Loading• Compaction• Volume
change• Subsidence
Liquifaction –
• When shaken the strength of the soil is lost
Shaking • earthquake • vibrations
from– roads – railroads
Shaking
• liquefaction
Expansive soils
• expansive clays – Bentonite– Montmorilonite
Expansive soils
• Expansive clays – Bentonite– Montmorilonite
Management
• Accept – do nothing• Avoid – plan away• Defend – build to protect against
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