Where these subsidences result over low extraction mines, the subsidence tends to be more sag-like, typically ranging in width from 500 to 1,000 feet and a maximum subsidence of one to four feet.
Sag- to trough-shaped subsidences do not only produce settlement but also cause the ground to shift horizontally up to about three feet.
The mineral rights can have restrictions, such as a no-surface subsidence clause.
Exposure of a pipeline to mine subsidence depends on the mining technique.
By nature, subsidence from high extraction mining is predictable.
This is because high extraction mining of coal causes immediate and severe subsidence movements on the ground surface.
Mining Underground Surface Type(*) Protection Protection High None: immediate None extraction subsidence Mitigation measures Mainly permanent None support via pillars or solid coal Low Same None Extraction Mining Damage Cost Type(*) High Damaged pipe ?
Although subsidence from high extraction mining areas is predictable, subsidence above low extraction areas is not.