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Questions and Answers
What is the modified percentage of clay in Soil C?
What is the modified percentage of clay in Soil C?
- 32.2%
- 40.5%
- 58% (correct)
- 45.5%
Which soil has the highest percentage of silt after modification?
Which soil has the highest percentage of silt after modification?
- Soil B
- Soil C
- Soil D
- Soil A (correct)
How is the modified percentage of sand calculated?
How is the modified percentage of sand calculated?
- Modified % sand = %sand / (100 - %gravel)
- Modified % sand = %sand x (100 - %gravel) (correct)
- Modified % sand = %sand x 100
- Modified % sand = %sand + %gravel
Which of the following correctly describes Soil B in terms of its texture classification?
Which of the following correctly describes Soil B in terms of its texture classification?
What percentage of sand is found in Soil D after modification?
What percentage of sand is found in Soil D after modification?
Which soil texture category does Soil A fall into based on its particle-size distribution?
Which soil texture category does Soil A fall into based on its particle-size distribution?
When calculating the modified percentage of sand for Soil D, what is the corrected formula applied?
When calculating the modified percentage of sand for Soil D, what is the corrected formula applied?
What is the primary method used to classify soil according to the USDA textural classification system?
What is the primary method used to classify soil according to the USDA textural classification system?
What percentage of clay is found in Soil C before modification?
What percentage of clay is found in Soil C before modification?
In the modified percentages, which soil has the highest percentage of clay?
In the modified percentages, which soil has the highest percentage of clay?
According to the USDA classification, which soil is most likely to be described as 'Sandy Loam'?
According to the USDA classification, which soil is most likely to be described as 'Sandy Loam'?
Which classification system indicates that fine grained soils should have more than 50% passing through the No. 200 sieve?
Which classification system indicates that fine grained soils should have more than 50% passing through the No. 200 sieve?
How do the AASHTO and USCS systems differ in their classification of gravelly and sandy soils?
How do the AASHTO and USCS systems differ in their classification of gravelly and sandy soils?
Which modified percentage of silt reflects the greatest proportion in Soil A?
Which modified percentage of silt reflects the greatest proportion in Soil A?
What misconception might arise about the moisture content in the soil classification process?
What misconception might arise about the moisture content in the soil classification process?
What is the group symbol for Soil A based on the provided solutions?
What is the group symbol for Soil A based on the provided solutions?
What percentage passes through the No. 200 sieve for Soil B to classify it correctly according to USCS?
What percentage passes through the No. 200 sieve for Soil B to classify it correctly according to USCS?
Which of the following correctly describes the classification of organic soils in AASHTO?
Which of the following correctly describes the classification of organic soils in AASHTO?
What sieve is used by USCS to separate gravel from sand?
What sieve is used by USCS to separate gravel from sand?
What is the group name for Soil B as per the solutions provided?
What is the group name for Soil B as per the solutions provided?
For fine grained soils, what is the passing percentage for AASHTO classification?
For fine grained soils, what is the passing percentage for AASHTO classification?
What plasticity index value or higher categorizes soil as clayey?
What plasticity index value or higher categorizes soil as clayey?
Which particle size is excluded from soil sample classification?
Which particle size is excluded from soil sample classification?
What value is taken for a negative group index in soil quality evaluation?
What value is taken for a negative group index in soil quality evaluation?
Which groups have a group index that is always 0?
Which groups have a group index that is always 0?
What is the correct formula for calculating the group index (GI)?
What is the correct formula for calculating the group index (GI)?
Which of the following is NOT a group specified in the AASHTO classification system?
Which of the following is NOT a group specified in the AASHTO classification system?
When rounding the group index, to what value is GI = 3.4 rounded?
When rounding the group index, to what value is GI = 3.4 rounded?
What is indicated when the fine fractions of a soil sample have a plasticity index under 11?
What is indicated when the fine fractions of a soil sample have a plasticity index under 11?
What is the primary focus of soil classification systems?
What is the primary focus of soil classification systems?
Which of the following is NOT one of the classification systems mentioned for soil?
Which of the following is NOT one of the classification systems mentioned for soil?
What size range does silt fall into according to the USDA classification method?
What size range does silt fall into according to the USDA classification method?
What does the term 'texture' refer to in soil classification?
What does the term 'texture' refer to in soil classification?
Which of the following is a classification name based on texture?
Which of the following is a classification name based on texture?
What are the particle size limits for sand according to the USDA classification method?
What are the particle size limits for sand according to the USDA classification method?
Which of the following classification methods emphasizes the engineering behavior of soil?
Which of the following classification methods emphasizes the engineering behavior of soil?
In the USDA classification system, what is the size range for clay particles?
In the USDA classification system, what is the size range for clay particles?
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Study Notes
Soil Classification Overview
- Soil classification provides a standardized language for describing soil characteristics.
- Classification systems simplify the diverse nature of soils through systematic methods.
Main Classification Systems
- U.S. Department of Agriculture (USDA) Classification System
- AASHTO Classification System
- Unified Soil Classification System (USCS)
Textural Classification
- Soil texture relates to its surface appearance, influenced by particle size.
- Three main sizes are defined:
- Sand: 2.0 to 0.05 mm in diameter
- Silt: 0.05 to 0.002 mm in diameter
- Clay: smaller than 0.002 mm in diameter
- Common terms include sandy clay and silty clay.
Comparison of AASHTO and USCS
- Both systems categorize soil into coarse and fine-grained based on particle size.
- AASHTO defines fine-grained soils as over 35% passing through the No. 200 sieve; USCS defines it as over 50%.
- In AASHTO, gravel and sand are not separated; in USCS, they are distinctly classified.
- Neither system provides a classification for organic soils.
Problem Solving in Soil Classification
- Classification involves determining group symbols and names based on sieve analysis and plasticity characteristics.
- Soil A identified as CL (Sandy Lean Clay).
- Soil B identified as SC (Clayey Sand with Gravel).
Particle-Size Distribution
- Displays the composition of gravel, sand, silt, and clay in various soil samples.
- Modified percentages take gravel content into account to provide a clearer classification.
USDA Textural Classification Problems
- The classification method interprets data from sieve analysis to categorize soil types accurately.
- Fine fractions with a plasticity index of 11 or more are labeled as clayey.
AASHTO Classification Details
- AASHTO categorizes soils into groups (A-1 to A-7) based on liquid limit and plasticity index.
- Group Index (GI) is a crucial evaluation metric for subgrade material quality.
- GI is calculated using a specific formula and adjusted for certain group inclusions.
Important Notes on Group Index
- Negative GI values are treated as zero.
- GI helps assess the suitability of soil for highway subgrade applications.
- Soils in groups A-1-a, A-1-b, A-2-4, A-2-5, and A-3 always have a GI of 0.
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