CE 210Dr SaMeH1 Soil Mechanics & Foundation 1 (CE 210) [8] Associate Professor of Environmental Eng. Civil Engineering Department Engineering College Majma’ah University faculty.mu.edu.sa/smohamed/SaMeH Feb Dr. Sameh S. Ahmed

Atterberg Limits CE 210Dr SaMeH2

Atterberg Limits CE 210Dr SaMeH3 Border line water contents, separating the different states of a fine grained soil Liquid limit Shrinkage limit Plastic limit liquidsemi- solid brittle- solid plastic water content 0

Purpose : This lab is performed to determine the plastic and liquid limits of a fine grained soil. The Atterberg limits are based on the moisture content of the soil. The plastic limit: is the moisture content that defines where the soil changes from a semi-solid to a plastic (flexible) state. The liquid limit: is the moisture content that defines where the soil changes from a plastic to a viscous fluid state. CE 210Dr SaMeH4

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The water content at which a soil changes from a plastic consistency to a liquid consistency. Defined by Laboratory Test concept developed by Atterberg in CE 210Dr SaMeH6 Liquid Limit Definition

liquid limit (LL) The liquid limit (LL) is arbitrarily defined as the water content, in percent, at which a pat of soil in a standard cup and cut by a groove of standard dimensions will flow together at the base of the groove for a distance of 12 mm under the impact of 25 blows in the devise. The cup being dropped 10 mm in a standard liquid limit apparatus operated at a rate of two shocks per second. CE 210Dr SaMeH7

Liquid Limit (w L or LL): Clay flows like liquid when w > LL Plastic Limit (w P or PL): Lowest water content where the clay is still plastic. Shrinkage Limit (w S or SL): At w<SL, no volume reduction on drying CE 210Dr SaMeH8 Atterberg Limits

Prepare paste of soil finer than 425 micron sieve Place Soil in Cup CE 210Dr SaMeH9 LL Test Procedure.. Step (1)

Step (2) Cut groove in soil paste with standard grooving tool CE 210Dr SaMeH10

Step (3) Rotate cam and count number of blows of cup required to close groove by 1/2” CE 210Dr SaMeH11

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Steps (4 to 6) Perform on 3 to 4 specimens that bracket 25 blows to close groove. Obtain water content for each test. Plot water content versus number of blows on semi-log paper. CE 210Dr SaMeH14

CE 210Dr SaMeH15 LLTest Results LL Test Results Log N water content, % LL= w% Interpolate LL water content at 25 blows 25

CE 210Dr SaMeH16 LL Values < 16 % not realistic 16 PI, % Liquid Limit, %

CE 210Dr SaMeH17 LL Values > 50 - HIGH Liquid Limit, % PI, % 50 H

CE 210Dr SaMeH18 LL Values < 50 - LOW Liquid Limit, % PI, % 50 L

CE 210Dr SaMeH19 Plastic Limit The minimum water content at which a soil will just begin to crumble when it is rolled into a thread of approximately 3 mm in diameter.

Using paste from LL test, begin drying. May add dry soil or spread on plate and air-dry. When point is reached where thread is cracking and cannot be re-rolled to 3 mm diameter, collect at least 6 grams and measure water content. Defined plastic limit. CE 210Dr SaMeH20 Plastic Limit w% procedure

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Plastic Limit w% procedure 1.Calculate the water content of each of the plastic limit moisture cans after they have been in the oven for at least 16 hours. 2.Compute the average of the water contents to determine the plastic limit, PL CE 210Dr SaMeH22

Plasticity Index is the numerical difference between the Liquid Limit w% and the Plastic Limit w% CE 210Dr SaMeH23 Definition of Plasticity Index w% LLPL PI = LL - PL Plasticity Index = Liquid Limit – Plastic Limit plastic (remoldable)

CE 210Dr SaMeH24 Plasticity Chart Low plasticityw L = < 35% Intermediate plasticityw L = % High plasticityw L = % Very high plasticityw L = % Extremely high plasticityw L = > 90%