Fracture (geology)
A fracture is any local separation or discontinuity plane in a geologic formation, such as a joint or a fault that divides the rock into two or more pieces. A fracture will sometimes form a deep fissure or crevice in the rock. Fractures are commonly caused by stress exceeding the rock strength, causing the rock to loose cohesion along its weakest plane.[1] Fractures can provide permeability for fluid movement, such as water or hydrocarbons. Highly fractured rocks can make good aquifers or hydrocarbon reservoirs, since they may possess both significant permeability and fracture porosity.
Causes
Fracturing in rocks can be formed either due to compression or tension. Fractures due to compression include thrust, normal, and strike-slip faults. Fractures due to tension can occur due to thermal contraction as rocks cool (with columnar basalt being a recognizable example), or due to stress fields in the near surface, such as those that produce radial dikes around a volcano.
Fractures are generally produced as strain due to natural stress on the rock, but they can also be created as a result of natural or man-made hydraulic fracturing.
Engineering considerations
In geotechnical engineering a fracture forms a discontinuity that may have a large influence on the mechanical behavior (strength, deformation, etc.) of soil and rock masses in, for example, tunnel, foundation, or slope construction.
See also
Notes
References
- Gudmundsson, Agust (2011) Rock Fractures in Geological Processes Cambridge University Press, Cambridge, England, ISBN 978-0-521-86392-6
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