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from article Rock mechanics

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Typical rock mass containing numerous discontinuities. The person in picture is conducting a scanline survey, where a tape is placed across the rock and detailed information is gathered on the fractures that intersect the scanline.

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from article Rock mechanics

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(a) Uniaxial compression test, where an axial stress is applied to a core sample of rock and increased until failure. (b) Triaxial compression test, where a constant confining stress is first applied, then the axial stress is increased until failure.

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from article Rock mechanics

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(a) Example of the failure zone around an underground excavation (×, shear failure; o, tensile failure), calculated using the Rocscience Phase2 computer program. (b) Example of a shallow underground excavation where the failure mode is either…

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from article Polypodiales

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Licorice fern (Polypodium glycyrrhiza), a member of the order Polypodiales, in Olympic National Forest, Washington. (Photo courtesy of the U.S. Department of Agriculture, Forest Service)

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from article Polypodiales

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Christmas fern (Polystichum acrostichoides). (Photo by James H. Miller, U.S. Department of Agriculture, Forest Service)

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from article Polypodiales

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The sensitive fern (Onoclea sensibilis), a representative of the Polypodiales. (After W. W. Robbins, T. E. Weier, and C. R. Stocking, Botany: An Introduction to Plant Science, 3d ed., Wiley, New York, 1964)

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from article Polypodiales

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Types of steles in the Polypodiales: (a) Protostele. (b) Amphiphloic siphonostele. (c) Ectophloic siphonostele. (d) Dictyostele with central pith surrounded by xylem and phloem in the form of discrete vascular bundles; bands of parenchyma cells…

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from article Polypodiales

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Life history of a fern: (1) the fern plant, or sporophyte, bearing sori, or clusters of sporangia, on its leaves; (2) a sporangium; (3) a tetrad of young spores; (4) the four mature spores that have come from the tetrad shown in part 3; (5) a spore…

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