Table of Contents
Atterberg limits tests establish the moisture contents at which fine-grained clay and silt soils transition between solid, semi-solid, plastic, and liquid states.
What do Atterberg Limits tell us?
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 Atterberg limits can be used to distinguish between silt and clay, and to distinguish between different types of silts and clays.
What are the Atterberg limits of LL and PL used for?
The Atterberg limits consist of the following key values of moisture content: The Liquid Limit (LL) is the moisture content at which a fine-grained soil no longer flows like a liquid. The Plastic Limit (PL) is the moisture content at which a fine-grained soil can no longer be remolded without cracking.
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.
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.
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 the difference between liquid limit and plastic limit called?
The difference between the liquid limit and the plastic limit is known as the plasticity index (IP), and it is in this range of water content that the soil has a plastic consistency. The consistency of most soils in the field will be plastic or semi-solid.
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.
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.
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 are the various consistency limits?
2. Historical background Swedish agriculture engineer ATTERBERG was the one who mentioned that a fine grained soil can exist in four states: liquid plastic semi-solid solid So consistency limits are also known Atterberg’s limits. 4.
What are the importance of Atterberg limits?
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.
Is high plasticity clay good?
A high PI indicates an excess of clay or colloids in the soil. Its value is zero whenever the PL is greater or equal to the LL. The plasticity index also gives a good indication of compressibility (see Section 10.3). The greater the PI, the greater the soil compressibility.
Why is there 25 blows in liquid limit?
The liquid limit is the moisture content at which the groove, formed by a standard tool into the sample of soil taken in the standard cup, closes for 10 mm on being given 25 blows in a standard manner. This is the limiting moisture content at which the cohesive soil passes from liquid state to plastic state.
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 a toughness index?
The toughness index is a measure of the shearing strength of the soil at the plastic limit.
What is plasticity in clay?
Plasticity is the outstanding property of clay–water systems. It is the property a substance has when deformed continuously under a finite force. When the force is removed or reduced, the shape is maintained.
Can liquidity index negative?
Yes 🙂 it can have have a negative value. A negative liquidity index means that the soil is drier that the plastic limit. Liquidity Index (LI) is a measure of the consistency of the soil. 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.
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.
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.
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 is number of blows in liquid limit?
The liquid limit is the moisture content at which the groove, formed by a standard tool into the sample of soil taken in the standard cup, closes for 10 mm on being given 25 blows in a standard manner.
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.
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.
