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Explanation & Answer
Here is your assignment :).
TEST NO. 1: TAKE HOME
1. Describe the USC and AASHTO soil classifications and list one similarity, one difference, one
advantage, and one disadvantage of each system.
Answer:
USC: This applied to most unconsolidated material represented by two letter symbol: 𝐺 =
𝑔𝑟𝑎𝑣𝑒𝑙, 𝑆 = 𝑠𝑎𝑛𝑑, 𝑀 = 𝑠𝑖𝑙𝑡, 𝐶 = 𝑐𝑙𝑎𝑦 𝑂 = 𝑜𝑟𝑔𝑎𝑛𝑖𝑐. Second letter: 𝑃 =
𝑝𝑜𝑜𝑟𝑙𝑦 𝑔𝑟𝑎𝑑𝑒𝑑 𝑊 = 𝑤𝑒𝑙𝑙 𝑔𝑟𝑎𝑑𝑒𝑑, 𝐻 = ℎ𝑖𝑔ℎ𝑙𝑦 𝑝𝑙𝑎𝑠𝑡𝑖𝑐, 𝐿 = 𝑙𝑜𝑤 𝑝𝑙𝑎𝑠𝑡𝑖𝑐𝑖𝑡𝑦.
AASHTO: This classification depends on three different soil properties: particles size
distribution, liquid limit, and plasticity index.
Similarity: Both classification considers finding the percentage of particles of soil in different
soil. The analysis is intensive in case of AASHTO a whole sieve analysis for low sieve is done.
Difference: USCS classification is based on sieve no 200, plasticity index and AASHTO is based
on plasticity index and group index value. In case of USC classification, coefficient of
uniformity and coefficient of curvature is used which helps to classify the soil to be well or poor
depending on their value and whether it is gravel or sand.
Advantage: UCS gives an idea about the distribution of larger sized particles and there range
with help of coefficient of curvature and coefficient of uniformity with help of AASHTO, we
have a lot of different groups for a single soil.
Disadvantage: AASHTO requires intensive or time talking sieve analysis as well as various other
limits such as liquid and plastic limit making it a very lengthy procedure. In UCS classification,
knowing the soil type is just dependent on soil size distribution and silt size, the factor other than
that are not kept in consideration.
2. Why do we have soil classification systems? What use are they?
Answer:
We need Soil classificatio...