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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.
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 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.
How many grades of soil are there?
Explanation: Based on the degree of distinctness of peds (natural aggregates of soil particles), there are 4 grades of soil. They are structureless, weak, moderate and strong.
What is weighted plasticity index?
The Weighted Plasticity Index (WPI) is defined as the value of the plasticity index (PI) times the % passing the 425 micron sieve. The Contractor must provide the calculations to verify the WPI.
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).
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.
What is plastic limit of soil?
Plastic limit is defined as the water moisture content at which a thread of soil with 3.2mm diameter begins to crumble.
What does the liquid limit tell us?
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.
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.
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.
Which soil has more plasticity index?
In general, Soils with a high PI tend to be clay, Those with a lower PI tend to be silt, and. Those with a PI near zero tend to have little or no silt or clay (fines) present.
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.
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.
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.
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.
How do you find the liquid limit?
Subtract the weight of a dry soil sample from the weight of a wet soil sample and multiply by 100. Divide the result by the weight of the wet sample to get the percent water content for that sample.
Is code for liquid limit and plastic limit?
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 is plastic soil?
“Plastic soil” generally means the soil is predominantly clay – and the more plastic the soil, the more expansive it will likely be. The soil’s plasticity is measured by two tests: the Plastic limit and 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 the importance of liquid limit test?
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 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 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.
