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Such fractures occur in planar parallel sets at an angle of 60 degrees and can be of the same size and scale as joints. As a result, some "conjugate joint sets" might actually be shear fractures. Shear fractures are distinguished from joints by the presence of slickensides, the products of shearing movement parallel to the fracture surface. The ...
fracture tip – the point at which the fracture trace terminates on the surface; fracture trace – the line representing the intersection of the fracture plane with the surface; Griffith cracks – preexisting microfractures and flaws in the rock; joint – a natural fracture in the formation in which there is no measureable shear displacement
A discontinuity may exist as a single feature (e.g. fault, isolated joint or fracture) and in some circumstances, a discontinuity is treated as a single discontinuity although it belongs to a discontinuity set, in particular if the spacing is very wide compared to the size of the engineering application or to the size of the geotechnical unit.
Columnar jointing is a geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms (basalt prisms), or columns. Columnar jointing occurs in many types of igneous rocks and forms as the rock cools and contracts.
Tensile stress forms joints in rocks. A joint is a fracture that forms within a rock, whose movement to open the fracture is greater than the lateral movement that takes place. Joints are formed in the direction perpendicular to the least principal stress, meaning that they are formed perpendicular to the tensile stress. [ 1 ]
In metamorphic geology, a compatibility diagram shows how the mineral assemblage of a metamorphic rock in thermodynamic equilibrium varies with composition at a fixed temperature and pressure. Compatibility diagrams provide an excellent way to analyze how variations in the rock's composition affect the mineral paragenesis that develops in a ...
In geology, strike and dip is a measurement convention used to describe the plane orientation or attitude of a planar geologic feature. A feature's strike is the azimuth of an imagined horizontal line across the plane, and its dip is the angle of inclination (or depression angle ) measured downward from horizontal. [ 1 ]
Clay minerals are phyllo-silicate, in other words, with sheet-like structure. [14] They are effective agents that block fluid flows across a fault zone. [ 14 ] Clay smears, deformed layers of clay, that are developed along fault zone can act as a seal of hydrocarbon reservoir i.e. extremely low permeability that nearly prohibits all fluid flows ...