Soil Classification Quiz

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Questions and Answers

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?

Soil B

Soil C

Soil D

Soil A (correct)

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?

Silty Clay Signup and view all the answers

What percentage of sand is found in Soil D after modification?

25% Signup and view all the answers

Which soil texture category does Soil A fall into based on its particle-size distribution?

Clay Loam Signup and view all the answers

When calculating the modified percentage of sand for Soil D, what is the corrected formula applied?

$rac{20}{100 - 12}$ Signup and view all the answers

What is the primary method used to classify soil according to the USDA textural classification system?

Sieve analysis performance Signup and view all the answers

What percentage of clay is found in Soil C before modification?

58% Signup and view all the answers

In the modified percentages, which soil has the highest percentage of clay?

Soil C Signup and view all the answers

According to the USDA classification, which soil is most likely to be described as 'Sandy Loam'?

Soil D Signup and view all the answers

Which classification system indicates that fine grained soils should have more than 50% passing through the No. 200 sieve?

Unified Soil Classification System (USCS) Signup and view all the answers

How do the AASHTO and USCS systems differ in their classification of gravelly and sandy soils?

USCS separates gravelly and sandy soils, while AASHTO does not. Signup and view all the answers

Which modified percentage of silt reflects the greatest proportion in Soil A?

45.6% Signup and view all the answers

What misconception might arise about the moisture content in the soil classification process?

Moisture has no effect on textural classification Signup and view all the answers

What is the group symbol for Soil A based on the provided solutions?

CL Signup and view all the answers

What percentage passes through the No. 200 sieve for Soil B to classify it correctly according to USCS?

58% Signup and view all the answers

Which of the following correctly describes the classification of organic soils in AASHTO?

There is no indication or classification for organic soils. Signup and view all the answers

What sieve is used by USCS to separate gravel from sand?

No. 4 sieve Signup and view all the answers

What is the group name for Soil B as per the solutions provided?

Clayey Sand with Gravel Signup and view all the answers

For fine grained soils, what is the passing percentage for AASHTO classification?

More than 35% Signup and view all the answers

What plasticity index value or higher categorizes soil as clayey?

11 Signup and view all the answers

Which particle size is excluded from soil sample classification?

Larger than 75 mm Signup and view all the answers

What value is taken for a negative group index in soil quality evaluation?

0 Signup and view all the answers

Which groups have a group index that is always 0?

A-2-4 and A-2-5 Signup and view all the answers

What is the correct formula for calculating the group index (GI)?

GI = (F₂₀₀ - 35)[0.2 + 0.005(LL - 40)] + 0.01(F₂₀₀ - 15)(PI - 10) Signup and view all the answers

Which of the following is NOT a group specified in the AASHTO classification system?

A-2-8 Signup and view all the answers

When rounding the group index, to what value is GI = 3.4 rounded?

3 Signup and view all the answers

What is indicated when the fine fractions of a soil sample have a plasticity index under 11?

The soil is not clayey. Signup and view all the answers

What is the primary focus of soil classification systems?

To express the general characteristics of soils concisely Signup and view all the answers

Which of the following is NOT one of the classification systems mentioned for soil?

Modified Soil Classification System (MSCS) Signup and view all the answers

What size range does silt fall into according to the USDA classification method?

0.05 to 0.002 mm Signup and view all the answers

What does the term 'texture' refer to in soil classification?

The size distribution of the soil particles Signup and view all the answers

Which of the following is a classification name based on texture?

Sandy clay Signup and view all the answers

What are the particle size limits for sand according to the USDA classification method?

2.0 to 0.05 mm Signup and view all the answers

Which of the following classification methods emphasizes the engineering behavior of soil?

Unified Soil Classification System (USCS) Signup and view all the answers

In the USDA classification system, what is the size range for clay particles?

Smaller than 0.002 mm Signup and view all the answers

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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Description

Test your knowledge on the various methods and systems used to classify soil. This quiz will help you recognize different soil types and solve problems related to soil classification. Perfect for students studying soil science or environmental engineering.