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17 Cards in this Set
- Front
- Back
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Arrangement of soils with similar properties into groups and subgroups |
Soil classification |
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Soils may be classified in a general way as: |
Cohesive vs. Cohesionless Fine grained vs. Course grained Residual vs. Transported |
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Need for soil classification system |
•language of communication bet. Engineers •enables one to use the engineering experience of others •engineering properties have found to correlate quite well with the index •engineer already has a fairly good general idea of the way the soil will behave |
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Soil classification system |
Grain-size classification Textural classification Classification by use |
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Limitations of grain size classification |
Gives only border bet. groups but does not give us a name for a given bulk of soil Natural soils are mixtures of particles from several size groups |
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Soil are named after their principal components |
Textural classification system |
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Texture of a soil depends on |
The relative sizes of the particles Range or distribution of these sizes Shapes of the particles |
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USDA |
US departmwnt of Agriculture |
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USCS |
Unified Soil Classification System |
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AASHTO |
American Association of State Highway and Transportation Officials |
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AASHTO test required: |
Grain size analysis Liquid limit Plastic limit |
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Soils containing fine-gtained materials are further identified by a number called... |
Group index |
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GI depends on: |
Percentage of the soil passing the no. 200 (0.075mm) sieve liquid limit Plasticity index |
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Rules foe determining GI |
1. If GI is negative value take it as zero 2. GI is rounded off to the nearest whole number 3. There is no upper limit for GI 4. The group index belonging to groups A-1-a, A-1b, A-2-4, A-2-5 and A-3 will always be zero 5. The GI for soils belonging to groups A-2-6 and A-2-7 is the partial group index 6. The group index value is written in parenthesis next to the AASHTO symbol 7. Tge higher the GI, the less desirable is the soil for use as a sub grade. GI=0 "good subgrade" GI > =20 " very poor subgrade" |
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This system was developed by arthur casagrande in 1942 |
USCS |
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Criteria for USCS |
Grain size Cu and Cc Plasticity chart |
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USCS test required |
Grain-size analysis Liquid limit Plastic limit |
