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Rock Cycle & Soil Origins Magma –> Igneous Rocks Intrusive, Extrusive Transportation, Erosion, Weathering Sediments -> Sedimentary Rock Metamorphism Melting.

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Presentation on theme: "Rock Cycle & Soil Origins Magma –> Igneous Rocks Intrusive, Extrusive Transportation, Erosion, Weathering Sediments -> Sedimentary Rock Metamorphism Melting."— Presentation transcript:

1 Rock Cycle & Soil Origins Magma –> Igneous Rocks Intrusive, Extrusive Transportation, Erosion, Weathering Sediments -> Sedimentary Rock Metamorphism Melting to Magma

2 Natural Soil Deposits Weathering Process Mechanical and Chemical Soil Types Residual - Formed in-place Transported – Glacial, Alluvial, Aeolian

3 Soil-Particle Size Coarse Grains Gravels - typically > 2 mm Sands – typically – 2 mm Fine Grains Silts – – mm Clays – typically < mm

4 Particle Size – Table 1.1 MIT – Initial classification system USDA – Textural classification system, agronomy AASHTO – Classification for road building purposes USCS – Predominant system used for geotechnical engineering

5 Clay Minerals Silica Tetrahedron Silica Sheet Alumina Octahedron Octahedral Sheet (Gibbsite) Different clay minerals built up of varying sheet combinations Become putty-like in presence of water

6 Clay Minerals Kaolinite – Large blocky particles 15 m 2 /g specific surface Illite – flake-shaped particles 80 m 2 /g Montmorillonite – Very flaky 800 m 2 /g

7 Specific Gravity Ratio of unit weight of material to the unit weight of water G s = ( s / ( w = M s / V s ( w Typically 2.6 to 2.9 Table 1.2 provides representative values

8 Mechanical Analysis Sieve Analysis Good to mm (#200) Dry - Mechanical shaker Wet – Hand separation Hydrometer Analysis Sedimentation Test Good to 1-2 :

9 Particle-Size Distribution Generally plotted on semi-log paper with % Passing vs. log size Provides simple visual aid for describing predominant size range and size distribution

10 Sieve No. Size mm Mass Ret g Indiv.% Retained Cumm % Retained % Passing Pan Table 1.4 Sieve Analysis

11 Size Distribution Curve

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13 Visual Interpretations

14 Shorthand Descriptors P xx – Percent passing sieve xx For example, P 200, P 1” R xx – Percent retained on sieve xx For example, R 200 P xx = 100 – R xx D xx – Diameter for which xx% is finer For example, D 10

15 Size Distribution Curve P4P4 #4 D 30 30

16 Numerical Descriptors Effective Size, D 10 Uniformity Coefficient, C u C u = D 60 / D 10 Coefficient of Gradation, C z C z = D 30 2 / D 60 D 10

17 Numerical Descriptors Coarse Grained Soils Gravels Well Graded if C u >4 and 16 and 1


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