Soil Mechanic Laboratory Introduction Moisture Content Unit Weight

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

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

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

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

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

Significance of this Class n Why do you need to learn about soils? Almost all structures are either constructed of soil, supported on soil, or both. n 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. 6

Transcosna Grain Elevator, Canada Oct. 18, 1913 West side of foundation 7

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

Shear Failure – Slope Stability 9

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

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

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

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

2 - Moisture Content – Sample Size n Minimum mass of moist material selected to be representative of the total samples: Maximum Particle Size (95 -100% Passing) Standard Sieve Size Recommended Min. Mass of moist specimen 2 mm or less # 10 20 g 4. 75 mm #4 100 g 9. 5 mm 3/8 -in 50 g 19. 0 mm ¾-in 250 g 37. 5 mm 11/2 -in 1000 g 75. 0 mm 3 -in 5000 g 14

2 - Moisture Content – Sample Calculation 15

3 - Specific Gravity, Gs n Definition; specific gravity, Gs, of soil solids is the ratio of the density of the aggregate soil solids to the density of water. r = 1 g/cm at 4 C n Mathematically, w 3 0 or rw = 62. 4 lb/ft 3 n ASTM D 854 n This method is applicable for soils composed of “Particles smaller than 4. 75 mm in size”. 16

3 - Specific Gravity – Sample Size n The procedure employs Archimedes’s principle “A body submerged in water will displace a volume of water equal to its own volume. ” n The key to successful application of this procedure is the removal of entrapped air n Recommended mass for test specimen Soil Type Specimen Dry Mass (g) 250 m. L Pycnometer Specimen Dry Mass (g) 500 m. L Pycnometer SP, SP-SM 60 ± 10 100 ± 10 SP-SC, SM, SC 45 ± 10 75 ± 10 Silt or Clay 35 ± 5 45 ± 10 17

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

3 - Specific Gravity – Expected Values n Expected Values for Gs Type of Soil Gs Sand 2. 65 - 2. 67 Silty sand 2. 67 – 2. 70 Inorganic clay 2. 70 – 2. 80 Soils with mica or iron 2. 75 – 3. 00 Organic soils < 2. 00 19

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

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

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

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

Specific Gravity (weight ratio) Unit weight of Water, w or rw n w = 1. 0 g/cm 3 (strictly accurate at 4° C) n w = 62. 4 pcf n w = 9. 81 k. N/m 3 24

Typical Values for Specific Gravity, Gs 25