Classification of soil from Geotechnical Engineering.pptx

Soil classification

1. Classifications of Soils Dr. Dipjyoti Baglari JIST, Jorhat

2. General Introduction Soil may be classified as: Cohesionless or coarse grained Cohesive or Fine grained But these are too general term and requires further classification Thus objective of soil classification system is to sort or group soils in different category, each group showing similar properties The most commonly used properties are grain size distribution and plasticity

3. Various soil classification system Unified soil classification system (USCS) American Assocation of state highway and Transport Officials (AASHTO) Indian Standard Soil classification System (ISSCS)

4. USCS System (Overview) The coarse grained soils are classified on the basis of their grain size distribution and the fine grained soils on the basis of their plasticity characteristics Here all the soils are classified in four major groups Coarse grained Fine grained Organic soils and peat Group symbols consisting of a prefix and suffix are used for various groups

5. USCS System (Overview) Coarse grained soils are those having 50% or more retained on 0.075mm sieve Coarse grained soil Gravel (G) Sand (S) The coarse soil is termed as Gravel (G) if 50% or more is retained on 4.75mm sieve otherwise termed S Both gravel and sand are further divided into GW and SW GP and SP GM and SM GC and SC

6. USCS System (Overview) Fine grained soils are those which has 50% or more passes through 0.074mm sieve Fine grained soil Silt Clay Based on its liquid limit and plasticity index

7. Plasticity Chart The A-line on the plasticity chart separates clay and silt (also organic soils) Silt, clay and organic soils are further classified into Low (L) and High (H) plasticity depending upon liquid limit

8. Indian Standard Soil classification System (ISSCS)