Soil Mechanic Laboratory Lect. Muhannd Waleed Majeed Soil Classification

1. Soil Mechanic LaboratoryLect. MuhanndWaleedMajeedSoil Classification Sources: Soil Mechanics – Laboratory Manual,B.M. DAS (Chapters 9)

2. Class Outlines • Soil Classification Systems • USCS • AASHTO • USDA • USCS Classification System

3. USCS Classification System • Originally developed for the United States Army • The method is standardized in ASTM D 2487 as “Unified Soil Classification System (USCS)” • USCS is the most common soil classification system among geotechnical engineers • A typical USCS classification would be: Silty sand with gravel SM - Group Name Group Symbol

4. Naming Convention • Fine-grained Soil First Letter Second Letter M – Silt L – Low plastic C – Clay H – High plastic O – Organic • Coarse-grained Soil First Letter Second Letter S – Sand P – Poorly graded G – Gravel W – Well graded M – Silty C - Clayey

5. Classification of Soils • From sieve analysis and the grain-size distribution curve determine the percent passing as the following: • > 3 inch – Cobble or Boulders • 3 inch - # 4 (76.2 – 4.75 mm) : Gravel • # 4 - # 200 (4.75 - 0.075 mm) : Sand • < # 200: Fines • First, Find % passing # 200 • If (5%) or more of soil passes # 200 sieve, then conduct Atterberg Limits test (LL & PL)

6. FINES GRAVEL SAND GrainSize Distribution Curves Cobbles or Boulders

7. Classification of Soils • If the soil is fine-grained (≥ 50% passes #200) follow the guidelines for fine-grained soils • If the soil is coarse-grained (<50% passes #200) follow the guidelines for coarse-grained soils • Find % Gravel & Sand • Calculate Cu & Cc • Calculate LL, PL and PI

8. Fine-grained Soils Civil Engineering - Texas Tech University

9. Coarse-grained Soils Civil Engineering - Texas Tech University

10. In your report • Use data from Sieve analysis in Lab 2 and classify the soil • Assuming the % passing No. 200 Sieve in 55%, and using data from Lab 3 classify the soil • Attach the Plasticity Chart