Soil Mechanic Laboratory Assist Lec Lubna Mohammed Abd
Soil Mechanic Laboratory Assist. Lec. Lubna Mohammed Abd Environmental Engineering Department Al- Mustansiriyah University Soil Classification Sources: Soil Mechanics – Laboratory Manual, B. M. DAS (Chapters 9)
Class Outlines n Soil Classification Systems n USCS n AASHTO n USDA n USCS Classification System
USCS Classification System n Originally developed for the United States Army n The method is standardized in ASTM D 2487 as “Unified Soil Classification System (USCS)” n USCS is the most common soil classification system among geotechnical engineers n A typical USCS classification would be: SM - Silty sand with gravel Group Symbol Group Name
Naming Convention n Fine-grained Soil First Letter M – Silt C – Clay O – Organic n Coarse-grained Soil First Letter S – Sand G – Gravel Second Letter L – Low plastic H – High plastic Second Letter P – Poorly graded W – Well graded M – Silty C - Clayey
Classification of Soils n From sieve analysis and the grain-size distribution curve determine the percent passing as the following: > 3 inch – Cobble or Boulders n 3 inch - # 4 (76. 2 – 4. 75 mm) : Gravel n # 4 - # 200 (4. 75 - 0. 075 mm) : Sand n < # 200: Fines n n First, Find % passing # 200 n If (5%) or more of soil passes # 200 sieve, then conduct Atterberg Limits test (LL & PL)
Cobbles or Boulders Grain Size Distribution Curves GRAVEL SAND FINES
Classification of Soils n If the soil is fine-grained (≥ 50% passes #200) follow the guidelines for fine-grained soils n If the soil is coarse-grained (<50% passes #200) follow the guidelines for coarse-grained soils Find % Gravel & Sand n Calculate Cu & Cc n Calculate LL, PL and PI n
Fine-grained Soils Civil Engineering - Texas Tech University
Coarse-grained Soils Civil Engineering - Texas Tech University
In your report n Use data from Sieve analysis in Lab 2 and classify the soil n Assuming the % passing No. 200 Sieve in 55%, and using data from Lab 3 classify the soil n Attach the Plasticity Chart
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