2. Plasticity and structure of soil Flashcards
The consistency of clays and other cohesive soils (finegrained soils) is greatly influenced by the _______ of the soil.
water content
Depending on the moisture content, the behavior of soil
can be divided into four basic states:
- Solid
- Semisolid
- Plastic
- Liquid
T or F. The water content at which a soil passes from one state to
another is the same for different soils.
False.
The water content at which a soil passes from one state to another is different for different soils
describe the consistency of finegrained soils with varying degrees of moisture content; defined several limits of consistency
Atterberg Limits
The moisture content (in %) at the point of transition from plastic to liquid state.
Liquid Limit (LL)
The moisture content, (in %), at the point of transition from semisolid to plastic state
.
Plastic Limit (PL)
The moisture content, (in %), at the point of transition from solid to semisolid state.
Shrinkage Limit (SL)
The water content at which a soil loses its adhesion to a metal blade.
Sticky Limit
The water content at which the grains cease to cohere to each other.
Cohesion Limit
Atterberg Limits = water content of the sample
Engineering Response
Atterberg limits = water contents at certain limiting or critical stages in soil behavior
Soil Behavior
The Atterberg limits are used for four general applications:
- To obtain general information about a soil and its strength, compressibility, permeability, shrinkage, and swell properties.
- Used in empirical correlations for some engineering properties
- For soil classification
- In construction specifications
The water content required to close a distance of ½ inch (12.7 mm) along the bottom of the groove after 25 blows is defined as the Liquid Limit.
Multi-Point Method (ASTM D-4318)
It is difficult to adjust the moisture content in soil to meet the required ½ inch closure of the groove at 25 blows. Hence, at least ___ tests for the same soil are made at varying w%, and then w% values are plotted against the logarithm of the number of blows, N.
4 tests
Why Semi logarithmic plot?
to visualize data with exponential growth or decay by compressing large values and expanding smaller ones, making trends easier to observe
determining the number of blows at one water content for a soil, and by a process of extrapolation determining the liquid limit; This formula generally yields good results for the number of blows between 20 and 30.
One-Point Method (ASTM D-4318)
Popular in Europe and Asia, the liquid limit is defined as the water content of soil that allows a cone to penetrate exactly 20 mm within 5 seconds.
Fall-Cone Method (British Standard – BS1377)
