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. The Atterberg limits can be used to distinguish between silt and clay, and to distinguish between different types of silts and clays.
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.
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.
What is the importance of soil consistency?
The water holding capacity and the movement of water through the soil for plants is determined by soil consistency. This consistency also determines the relative resistance of the soil to pressure. The soil consistency is usually analyzed at three moisture levels – dry, moist and wet.
Why do we find the liquid limit of soil?
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.
How can you tell if plastic is clay?
As with other types of materials, a compression test can be used to evaluate the plasticity of clays. Baran et al. formulated their workability concept for clays using compression tests in cylindrical samples, allowing to determine the optimum amount of moisture for each clay studied.
How can one determine Atterberg limits?
Atterberg Limits Test Procedure: Liquid Limit is measured by spreading a portion of the soil sample in the brass cup of a liquid limit machine and dividing it using a grooving tool. The moisture content when the groove closes for 1/2in after 25 drops of the cup is defined as the Liquid Limit.
Why do we need Atterberg limits?
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 does the plastic limit tell us?
The plastic limit (PL) The percentage moisture content at which a soil changes with decreasing wetness from the plastic to the semi- solid consistency or with increasing wetness from the semi-solid to the plastic consistency. The plastic limit is the lower limit of the plastic state.
What is the purpose of liquid limit?
Liquid Limit It is the minimum moisture content at which a soil flows upon application of very small shear force. The precise definition of the liquid limit is based on standard test procedures. Liquid Limit can be determined using the Casagrande cup method or a cone penetrometer.
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 plastic limit of soil?
DEFINITION. 2.1 The plastic limit of a soil is the moisture content, expressed as a percentage of the weight of the oven-dry soil, at the boundary between the plastic and semisolid states of consistency. It is the moisture content at which a soil will just begin to crumble when rolled into a thread ⅛ in.
What is a high plastic limit?
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.
What is 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.
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.
At what diameter will a soil thread starts to crumble when it reaches the plastic limit?
The plastic limit is when a thread of soil rolled out on a nonporous surface begins to crumble when it reaches 1/8 in in diameter.
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 a good liquid limit of soil?
9.2. 1 Consistency and Plasticity
| Soil | Liquid limit wL (%) | Plastic limit wp (%) |
|---|---|---|
| Silt, medium plasticity | 35–50 | 22–23 |
| Clay, low plasticity | 25–35 | 15–22 |
| Clay, medium plasticity | 40–50 | 18–25 |
| Clay, high plasticity | 60–85 | 20–35 |
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 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 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.
