Similarly, the moisture content to another sample is determined and calculated the average value of percent of the moisture content, which is defined as plastic limit. Then percentage of the moisture content is determined from the above reading. The dry samples are weighed for the moisture content of soil. The thread is then folded and rolled repeatedly until the 3 mm thread begins to crumble.Īll threads are collected into the container and placed on the oven for drying. The thread is then rolled on a glass plate until its diameter is reduced to about 3 mm. Part of the soil sample is formed into a thread, about 6 mm in diameter between the first finger and thumb of each hand.
The dry soil that passing 0.425 mm test sieve is mixed with distilled water until it becomes sufficiently plastic to be mould into a ball.
Plastic limit is the moisture content at which a soil when rolled in to thread of smallest diameter possible starts crumbling and has a diameter of 3 mm. Plastic index thus indicates the range of moisture content over which the soil is in a plastic condition. Identify the importance and application of plastic limit test.
#PLASTIC LIMIT TEST FREE#
This device consists of a metal plate with a hard rubber base that can to rise in a specific way by rotating the hand for a distance of 1 cm that can be adjusted before starting the experiment and then the plate falls free to the base. Plasticity index (PI) is defined as the numerical difference between the liquid limit and plastic limit. For a plastic and liquid limits test, you will need the following. Thus these tests are used widely in the preliminary stages of designing any structure to ensure that the soil will have the correct amount of shear strength and not too much change in volume as it expands and shrinks with different moisture contents.Plastic limit is defined as the minimum moisture content at which the soil remains in a plastic state. The shrinkage limit of soil is calculated by the formula: W S ( M 1 M 2) ( V 1 V 2) w M 2. Clays and silts interact with water and thus change sizes and have varying shear strengths. These tests are mainly used on clayey or silty soils since these are the soils which expand and shrink when the moisture content varies. The amount of expansion is related to the ability of the soil to take in water and its structural make-up (the type of minerals present: clay, silt, or sand). DESCRIPTORS- soil/soil tests/ Atterberg limits/ liquid limit/ plastic limit/ drop cone/ fall cone cone penetrometer/ shear strength/ drop cone penetrometer. Soils when wet retain water, and some expand in volume ( smectite clay). They were later refined by Arthur Casagrande, an Austrian-born American geotechnical engineer and a close collaborator of Karl Terzaghi (both pioneers of soil mechanics).ĭistinctions in soils are used in assessing soil which is to have a structure built on them. These limits were created by Albert Atterberg, a Swedish chemist and agronomist, in 1911. AASHTO T 87 Dry Preparation of Disturbed Soil and Soil Aggregate Samples for Test. The plastic limit determines the lowest moisture content of a soil, by wich a sample can be rolled into threads 3 mm without breaking the same neither. REFERENCES: California Test 226 Determination of moisture content by Oven Drying.
The water content at which soil changes from one state to the other is known as consistency limits, or Atterberg's limit. This test method describes the procedures for determining the liquid limit, plastic limit, and plasticity index of a soil including cement or lime treated soils. The Atterberg limits can be used to distinguish between silt and clay and to distinguish between different types of silts and clays. Thus, the boundary between each state can be defined based on a change in the soil's behavior. This method describes the procedure for the determination of the Plastic Limit of soils and granular pavement materials. By measuring the liquid limit, plastic limit, and water content of the soil, the adhesiveness index can be calculated and compared with Fig. In each state, the consistency and behavior of soil are different, and consequently so are its engineering properties. Hollmann and Thewes 37 proposed a method for evaluating the risk of clogging in shield tunnelling through soil with high clay content based on the Atterberg limits and the actual water content of the soil. Geotechnical characteristics of a soil related to its water contentĭepending on its water content, soil may appear in one of four states: solid, semi-solid, plastic and liquid.
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