Table of Contents
Plastic Limit (PL) is the water content at the change from a plastic to a semi-solid state. This test involves repeatedly rolling a soil sample into a thread until it reaches a point where it crumbles.
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 the 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.
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.
Is code for plastic limit?
DETERMINATION OF PLASTIC LIMIT AND PLASTICITY INDEX Page 4 STANDARDS • IS: 2720 (Part-5) 1985. OBJECTIVE • Plastic limit is defined as minimum water content at which soil remains in plastic state. APPARATUS • Porcelain evaporating dish about 12cm in diameter. Flat glass plate 10mm thick and about 45cm square or longer.
What is a good plasticity index?
In general, the plasticity index depends only on the amount of clay present. It indicates the fineness of the soil and its capacity to change shape without altering its volume. 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.
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.
What does 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.
How do you find the plastic limit?
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.
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.
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).
How important is 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.
How do you find the liquid limit?
The tester places soil samples with varying water contents into the cup of the device, then cuts a groove through the sample. The cup is dropped multiple times until soil fills the groove. Use the number of drops along with the water content of the samples to calculate the liquid limit.
What does a low plastic limit mean?
The Plastic Limit, also known as the lower plastic limit, is the water content at which a soil changes from the plastic state to a semisolid state. OR. The soil moisture content at which any increase in the moisture content will cause a semi-solid soil to become plastic.
What is a high liquid limit?
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 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 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 elastic limit and plastic limit?
Answer: A load that exceeds the elastic limit deforms the material into the plastic region, which means that the material is permanently deformed when the load is removed. The plastic limit occurs when the material reaches the maximum plastic deformation – the breaking point.
What is Atterberg limit test?
Atterberg limits is a basic measure of the critical water content of fine-grained soils. These tests include shrinkage limit, plastic limit, and liquid limit, which are outlined in ASTM D4318. Depending on the water content of a soil, it may appear in four states: solid, semi-solid, plastic and liquid.
What is the liquid limit of soil?
Liquid limit is the water content where the soil starts to behave as a liquid. Liquid limit is measured by placing a clay sample in a standard cup and making a separation (groove) using a spatula. The cup is dropped till the separation vanishes. The water content of the soil is obtained from this sample.
