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Soil Mechanics Laboratory: Moisture Content, Unit Weight, and Specific Gravity Relationships

Learn about soil properties through lab tests like moisture content determination, unit weight measurement, and specific gravity calculation. Understand the importance and application of these tests in civil and environmental engineering. Significance of soil knowledge in construction and structural integrity.

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Soil Mechanics Laboratory: Moisture Content, Unit Weight, and Specific Gravity Relationships

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  1. Soil Mechanic LaboratoryIntroductionMoisture Content, Unit Weight, Specific Gravityand Phase Relationships Assist. Lec. Lubna Mohammed Abd Sources: Soil Mechanics – Laboratory Manual, B.M. DAS (Chapters 2 - 3) 1 Environmental Engineering Department Al- Mustansiriyah University

  2. Class Outlines 2 Handouts: Syllabus, Report Format Significance of the Class Lab test No.1: Moisture Content, Specific gravity and Unit Weight of soil Background: Phase Relationship

  3. Syllabus 3 • Text books: • Soil Mechanics: Laboratory Manual by Braja M. Das • Lecture Notes • ASTM Standards 2005 • Class organization • 1 hours lab per week in Wednesday for second class in first term of 2018-2019

  4. Report Format 4 • Each group will submit one report • Three to four students per group • Reports are prepared in the next week directly after performance the test • All reports should follow the report format • Title and group names • Purpose & Objective • Apparatus & Procedures • Deviation from ASTM Standards • Table of results • Figures • Sample Calculations • Discussion and Conclusion

  5. Report Format - Conclusion 5 Report your results (use a table) Do the results fall within the expected range or not?(Check tables and match your results) If not, Explain why (what went wrong?)

  6. Significance of this Class 6 • Why do you need to learn about soils? Almost all structures are either constructed of soil, supported on soil, or both. • Who must be concerned with soils? Civil engineers (structural, environmental and geotechnical) must have basic understanding of the soil properties in order to use them effectively in construction.

  7. Transcosna Grain Elevator, CanadaOct. 18, 1913 7 West side of foundation sank 24-ft

  8. Settlement Palacio de las Bellas, Artes, Mexico City Leaning Tower, Pisa 8

  9. Shear Failure – Slope Stability 9

  10. Organization of the Lab Tests Soil Properties Physical (Soil Characteristics) Mechanical Moisture Content Unit Weight Specific Gravity Gradation Atterberg Limits Permeability Strength (Shear) Compressibility (Soil Classification) Geotechnical engineeringStructural engineeringPavement engineering Geotechnical engineeringStructural engineeringPavement engineeringEnvironmental engineering 10

  11. Today’s Lab 11 Determination of unit weight (density) Determination of moisture content Determination of specific gravity Establishing the phase (weight-volume) relationship diagram

  12. 1- Unit Weight, g • Take several measurements for diameter and height • Take the average for H, D • Calculate g D H 12

  13. 2- Moisture Content, w Mw – Mass of watersMs – Mass of solidsMT – Total mass 13 Definition: Moisture content is an indicator of the amount of the water present in soil. Moisture content, w(%) ASTM 2216 (Conventional Oven Method) ASTM D 4643 (Microwave Oven Method) 3 minutes at 50% Power (mass ≈ 50 g)

  14. 2- Moisture Content – Sample Size • Minimum mass of moist material selected to be representative of the total samples: 14

  15. 2- Moisture Content – Sample Calculation 15

  16. 3- Specific Gravity, Gs rw = 1 g/cm3 at 40C or rw = 62.4 lb/ft3 16 Definition; specific gravity, Gs, of soil solids is the ratio of the density of the aggregate soil solids to the density of water. Mathematically, ASTM D 854 This method is applicable for soils composed of “Particles smaller than 4.75mm in size”.

  17. 3- Specific Gravity – Sample Size • The procedure employs Archimedes’s principle “A body submerged in water will displace a volume of water equal to its own volume.” • The key to successful application of this procedure is the removal of entrapped air • Recommended mass for test specimen 17

  18. 3- Specific Gravity - Apparatus Report Gs in terms of GS (200C) A – From Table 3-2 Pg 12 18 See Example in Table 3-3 Pg 13

  19. 3- Specific Gravity – Expected Values • Expected Values for Gs 19

  20. Phase Relationships: A 3-Phase Material Air Water Solid 20

  21. The Mineral Skeleton Solid Particles Volume Voids (air or water) 21

  22. Air Water Solids Three Phase Soil (Partially Saturated) Idealization: Three Phase Diagram Mineral Skeleton 22

  23. Air Wa~ 0 Water Ww WT Ws Solids Weight Relationships (weight -ratios) • Weight ratios • Moisture Content, w • Specific Gravity, Gs • Weight Components: • Weight of Solids = Ws • Weight of Water = Ww • Weight of Air, Wa~ 0 23

  24. Specific Gravity (weight ratio) Unit weight of Water, w or rw • w = 1.0 g/cm3 (strictly accurate at 4° C) • w = 62.4 pcf • w = 9.81 kN/m3 24

  25. Typical Values for Specific Gravity, Gs 25

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