Table of Contents
The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit.
What are the three 3 Atterberg limits?
There are three important Atterberg limits: shrinkage limit (SL), plastic limit (PL), and liquid limit (LL). The shrinkage limit is the water content at which the volume of the soil starts to increase.
How are Atterberg limits related to soil composition?
Atterberg Limits are the water contents which define transitions between the solid, plastic, and liquid states of a given soil material. The tests are restricted to cohesive soils with appreciable silt or clay fraction, and cannot be conducted readily on either sands or silts with a high sand fraction.
What are the limits of consistency?
A gradual increase in water content causes the soil to change from solid to semi-solid to plastic to liquid states. The water contents at which the consistency changes from one state to the other are called consistency limits (or Atterberg limits).
Is plasticity a chart?
A plasticity chart , based on the values of liquid limit (WL) and plasticity index (IP), is provided in ISSCS to aid classification. The ‘A’ line in this chart is expressed as IP = 0.73 (WL – 20). Depending on the point in the chart, fine soils are divided into clays (C), silts (M), or organic soils (O).
Why is the liquid limit important?
Value of liquid limit is used to classify fine grained soil. It gives us information regarding the state of consistency of soil on site. Liquid limit of soil can be used to predict the consolidation properties of soil while calculating allowable bearing capacity & settlement of foundation.
Why plastic limit test is done?
Plastic limit test is one of the laboratory tests used internationally to differentiate or classify soils into groups. When the water content or moisture content of soil increases beyond a limit then the soil starts to behave as liquid.
What is a toughness index?
The toughness index is a measure of the shearing strength of the soil at the plastic limit.
What are the significance of consistency limits?
Consistency limits are very significant in the study of clays and other fine-grained soils. Important deductions can be made based on the relative values of consistency limits and the index properties as follows: 1. The liquid limit and plasticity index are extremely useful for the classification of soils.
Can the liquid limit of a soil be greater than 100?
For Attapulgite, the liquid limit varies from 150 to 250, which are greater than 100 and the shrinkage limit varies from 100 to 125 which are also greater than 100. Therefore, the Atterberg’s limits can be greater than 100.
What do Atterberg Limits tell us?
In the field, the Atterberg Limits, can be used as a guide indicating how much a soil is likely to settle or consolidate under load. If the field moisture is near the liquid limit, a lot of settlement is likely. The opposite is true if the field moisture is near or below the plastic limit.
What does the plastic limit tell you?
Plastic Limit (PL) is the water content at the change from a plastic to a semi-solid state. Shrinkage Limit (SL) is the water content where the further loss of moisture does not cause a decrease in specimen volume.
What is a good plasticity index?
Some critical values of the plasticity index for aquaculture To construct a pond dike without a clay core*, the plasticity index of the soil material should have a value between 8 and 20 percent. For best compaction, the PI should be as close to 16 percent as possible (see Section 10.3).
What is Atterberg limit of soil?
The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit. The water content at which the soils change from one state to the other are known as consistency limits or Atterberg’s limit.
What is the plastic limit?
The plastic limit is the water content at which a soil-water paste changes from a semisolid to a plastic consistency as it is rolled into a 3.175-mm (1/8-inch) diameter thread in a standard test.
What is Liquidity Index?
The liquidity index (LI) is used for scaling the natural water content of a soil sample to the limits. It can be calculated as a ratio of difference between natural water content, plastic limit, and liquid limit: LI=(W-PL)/(LL-PL) where W is the natural water content.
What is the consistency index?
Consistency Index (CI)- This is a measure of how well an individual character fits on a phylogenetic tree. It is calculated by dividing the minimum possible number of steps by the observed number of steps.
Why is plastic limit important?
The plastic limit (PL) is the water content, in percent, at which a soil can no longer be deformed by rolling into 3.2 mm (1/8 in.) Those limit of soil are very important property of fine grained soil and its Value is used to classify fine grained soil and calculate activity of clays and toughness index of soil.
Is code for Atterberg limits?
STANDARD • IS: 2720 (Part 5) 1985. DEFINITION • Liquid Limit is defined as the water content at which the soil changes from liquid state to plastic state. APPARATUS • Casagrande apparatus confirming to IS: 9259-1979. Grooving tool.
Can you have a negative plasticity index?
Yes 🙂 it can have have a negative value. A negative liquidity index means that the soil is drier that the plastic limit. It merely describes the moisture condition of a soil with respect to its index limits.
What does a high plastic limit mean?
A high liquid limit normally indicates a high compressibility and a high shrinkage/swelling potential. A high-plasticity index Ip generally results in a low shear strength. A low Ip means that a soil used as foundation will change significantly in consistency even with a small change in water content.
How is plastic limit calculated?
Calculate the plastic limit wp by dividing the “weight of moisture” by the “dry weight of sample” and multiply by 100. Plasticity Index (Ip) of a soil is the numerical difference between its Liquid Limit and its Plastic Limit.
