41.%20Earth%20Materials

41.%20Earth%20Materials - Earth Materials Lecture 4 Earth...

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Unformatted text preview: Earth Materials Lecture 4 Earth Materials Lecture 4: Earth Materials Page 1 of 21 Lecture 4: Earth Materials Rocks and Minerals Naturally occurring Earth material formed through the rock forming process Durable material used in an engineered project Lecture 4: Earth Materials Page 2 of 21 Lecture 4: Earth Materials Durable material suitable to produce an image The parent material from which soils are formed Lecture 4: Earth Materials Page 3 of 21 Lecture 4: Earth Materials Aggregates of one or more minerals that comprise an appreciable part of the Earth’s crust Mineral ► Naturally occurring ► Homogeneous ► Inorganic substance, having unique chemical composition and atomic arrangement Lecture 4: Earth Materials Page 4 of 21 Lecture 4: Earth Materials Rock Forming Processes ► Igneous melt = formed of fire; cooled from a Extrusive Intrusive Rock Forming Processes ►Sedimentary = To settle out, formed by deposition (Sedimentum) High Energy Low Energy Lecture 4: Earth Materials Page 5 of 21 Lecture 4: Earth Materials Rock Forming Processes ►Metamorphic = To transform, formed from other rocks by temperature and pressure Rock Cycle Lecture 4: Earth Materials Page 6 of 21 Lecture 4: Earth Materials Density (Unit Weight) of Common Materials Particle size and distribution Particle size and vertical grain-size distribution can be used to determine depositional conditions Lecture 4: Earth Materials Page 7 of 21 Lecture 4: Earth Materials Rock Description ► Geologic Rock Description Rock Environment of formation Environment Classification Rock Substance Properties ► Intact rock sample ► Unconfined compressive strength ► Deformation characteristics Lecture 4: Earth Materials Page 8 of 21 Lecture 4: Earth Materials Rock Mass Classification ► Three dimensional field conditions From Kingdom to Coal Lecture 4: Earth Materials Page 9 of 21 Lecture 4: Earth Materials Rock Substance Rock Strength ► Deformation characteristics ► Rock Strength ► Compressive strength of an intact sample Very High………………………..>32,000 psi High………………....…16,000—32,000 Medium…………….……8,000—16,000 Low……………………..….4,000—8,000 Very Low………….………………<4,000 Lecture 4: Earth Materials Page 10 of 21 Lecture 4: Earth Materials Deformation Characteristics ► Character of the stress-strain curve Elastic Elastic Plastic-elastic Plastic Elastic-plastic Elastic Plastic-elastic-plastic Plastic Elastic Crystalline or wellCrystalline cemented rock of uniform mineralogy quartzite, basalt Lecture 4: Earth Materials Page 11 of 21 Lecture 4: Earth Materials Plastic-Elastic Loose, porous sedimentary rocks of uniform mineralogy Initial loading closes pores – final loading is elastic quartz sandstone Elastic-Plastic Crystalline rocks composed of a mixture of minerals Elastic loading because there are no void spaces to close Plastic failure controlled by mineralogy of rock granite, gneiss Lecture 4: Earth Materials Page 12 of 21 Lecture 4: Earth Materials Plastic-Elastic-Plastic ► Porous sedimentary rocks composed of a mixture of minerals Initial compaction Progressive failure shale, coal ► ► Material Deformation Orientation of rock fabric impacts their physical properties Lecture 4: Earth Materials Page 13 of 21 Lecture 4: Earth Materials Deformation Mode Orientation of the sample relative to the direction of loading can produce significantly different responses Impact of Temperature Lecture 4: Earth Materials Page 14 of 21 Lecture 4: Earth Materials Impact of Confining Pressure Impact of Loading Rate Lecture 4: Earth Materials Page 15 of 21 Lecture 4: Earth Materials Rock Mass Classification ► Total Rock Body ► Description of the Discontinuities Bedding Bedding Fractures Fractures Rock Character Rock Folding Folding Faulting Faulting Bedding Thick (Massive) vs. Thin (Layered) >2m (6ft) Lecture 4: Earth Materials <2m (6ft) Page 16 of 21 Lecture 4: Earth Materials Fracture Spacing ► Very Wide………………………..>3m (9ft) ► Wide…………………….…..1 – 3m (3-9ft) ► Moderately Wide....30cm – 1m (1-3ft) ► Close………………….5 – 30cm (2-12 in) ► Very Close…………………..<5cm (<2in) RQD ► Rock Quality Designation ► RQD = Percentage of core recovered longer than 10 cm ► RQD = 98/150 65% 65% Lecture 4: Earth Materials Page 17 of 21 Lecture 4: Earth Materials RQD: Rock Description ► Very Poor……………..……………….<25% ► Poor…………………………….…..25 – 30% ► Fair………………………………….30 – 75% ► Good………………………………..75 – 90% ► Excellent………………………………..>90% Fracture Spacing vs. RQD vs. RQD Fracture Spacing RQD ► Very Close……………..………….Very Poor ► Close………………………………………..Poor ► Moderately Wide…………………………Fair ► Wide……………………………………….Good ► Very Wide………………..………..Excellent Lecture 4: Earth Materials Page 18 of 21 Lecture 4: Earth Materials Dangers of RQD ► One dimensional evaluation ► Limited to core recovery ► Evaluates entire core length rather than each foot ► Measures ONLY what was intercepted in core Character of Fractures Lecture 4: Earth Materials Page 19 of 21 Lecture 4: Earth Materials Fracture Continuity Impact on Tunnels Lecture 4: Earth Materials Page 20 of 21 Lecture 4: Earth Materials Break Lecture 4: Earth Materials Page 21 of 21 Lecture 4: Earth Materials ...
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