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Measuring rock mass damage in drifting
Published in B. Mohanty, Rock Fragmentation by Blasting, 2020
M. Paventi, Y. Lizotte, M. Scoble, B. Mohanty
The final DM component was the orientation of the drift axis with respect to the direction of the prevailing meso- and macro-structure. This component accounts for the most persistent and abundant meso-structures encountered in the drifts. It is calculated by addition of the cosines of the angle between the drift direction and the structure involved. Damage was observed to increase as structures approached the drift direction. Studies by Worsey et al. (1981) showed that a relationship exists between discontinuity orientation and fracture propagation. This was found to apply with the meso- and macro-structures at Birchtree. There are four types of meso-structure to consider: foliation, cleavage and jointing for metamorphic, lineation and jointing for igneous rocks and bedding, cleavage and possibly jointing (if < 2 m spacing) for sedimentary rocks.
Failure criteria for transversely isotropic rock
Published in Xia-Ting Feng, Rock Mechanics and Engineering, 2017
The constitutive laws and failure criteria of rock materials and rock masses are required in most rock engineering analyses that are based on solid mechanics. Due to the preferred fabric orientation or the existence of non-random discontinuity, anisotropic behaviors of rock masses should be fully accounted for in the analysis. Several types of rocks such as sedimentary rocks and metamorphic rocks may be transversely isotropic. Most foliated metamorphic rocks, such as schist, slates, gneisses, and phyllites contain fabric with preferentially parallel arrangements of flat or long minerals. Metamorphism changes the initial fabric of rocks with the directional structure. Foliation induced by the non-random orientation of macroscopic mineral, parallel fracture or microscopic mineral plates, such as fracture cleavage, slaty cleavage, bedding cleavage, lepidoblastic schistosity, nematoblastic schistosity or lineation leads to rock properties that are highly direction-dependent (Goodman, 1993). Stratified sedimentary rocks like sandstone, shale or sandstone–shale alteration often display anisotropic behaviors. The anisotropy may also be found in the isotropic rocks, such as granite and basalt, if cut by regular discontinuities (Amadei, 1983; Wittke, 1990).
Recognising the different types of building stone
Published in John A. Hudson†, John W. Cosgrove, Understanding Building Stones and Stone Buildings, 2019
John A. Hudson†, John W. Cosgrove
Following the explanation of Figure 3.72(a), the photograph of a small slate block, Figure 3.72(c), shows the key features: namely, the large cleavage plane with the through-going bedding (the set of horizontal lines) and on the joint surface indicated by the red dot, the fainter vertical lineation of the cleavage planes. This sample was taken from the hinge region of a fold as indicated in Figure 3.72(a); we know this because it is the only location where the bedding and cleavage planes are at right angles to each other. Note that an example of slate used as a roofing material is illustrated in Chapter 8, Figures 8.5 and 8.6.
Deformation and mineralisation in the Scotty Creek Basin, Agnew district, Eastern Goldfields, Western Australia: evidence for D1- and D3-related gold mineralisation
Published in Australian Journal of Earth Sciences, 2019
S. Jones, A. Waters, P. M. Ashley
An L1 mineral lineation is observed in strongly foliated mafic and ultramafic units that lie above the foliated granite around the margins of the Agnew granitic complex. In the granite, the L1 mineral lineation is predominantly defined by an alignment of recrystallised quartz, feldspar and minor biotite, and in the mafic–ultramafic units L1 mineral lineations are predominantly defined by an alignment of amphibole. The L1 mineral lineations display a radial pattern about the Agnew granitic complex (Figure 5), which is similar to a map shown in Blewett et al. (2010).
Unravelling the D1 event: evidence for early granite-up, greenstone-down tectonics in the Eastern Goldfields, Western Australia
Published in Australian Journal of Earth Sciences, 2021
S. A. Jones, K. F. Cassidy, B. K. Davis
Gently north-plunging L1 mineral lineations are present in strongly foliated mafic and ultramafic units that lie above the foliated granite around the margins of the Agnew granitic complex. In granite, the L1 mineral lineation is predominantly defined by an alignment of recrystallised quartz, feldspar and minor biotite, and in the mafic–ultramafic units L1 mineral lineations are predominantly defined by an alignment of amphibole.