Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
|Publication Date:||10 August 1998|
|ICS Code (Earthworks. Excavations. Foundation construction. Underground works):||93.020|
1.1 This test method covers the determination of the liquid limit, plastic limit, and the plasticity index of soils as defined in Section 3.
1.2 Two procedures for preparing test specimens are provided as follows: Wet preparation procedure, as described in 10.1. Dry preparation procedure, as described in 10.2. The procedure to be used shall be specified by the requesting authority. If no procedure is specified, use the wet preparation procedure.
1.2.1 The liquid and plastic limits of many soils that have been allowed to dry before testing maybe considerably different from values obtained on undried samples. If the liquid and plastic limits of soils are used to correlate or estimate the engineering behavior of soils in their natural moist state, samples should not be permitted to dry before testing unless data on dried samples are specifically desired.
1.3 Two methods for determining the liquid limit are provided as follows: Method A, Multipoint test as described in Sections 11 and 12. Method B, One-point test as described in Sections 14 and 15. The method to be used shall be specified by the requesting authority. If no method is specified, use Method A.
1.3.1 The multipoint liquid limit method is generally more precise than the one-point method. It is recommended that the multipoint method be used in cases where results maybe subject to dispute, or where greater precision is required.
1.3.2 Because the one-point method requires the operator to judge when the test specimen is approximately at its liquid limit, it is particularly not recommended for use by inexperienced operators.
1.3.3 The correlations on which the calculations of the one-point method are based may not be valid for certain soils, such as organic soils or soils from a marine environment. It is strongly recommended that the liquid limit of these soils be determined by the multipoint method.
1.4 The plastic limit test is performed on material prepared for the liquid limit test.
1.5 The liquid limit and plastic limit of soils (along with the shrinkage limit) are often collectively referred to as the Atterberg limits. These limits distinguished the boundaries of the several consistency states of plastic soils.
1.6 The composition and concentration of soluble salts in a soil affect the values of the liquid and plastic limits as well as the water content values of soils (see Method D 2216). Special consideration should therefore be given to soils from a marine environment or other sources where high soluble salt concentrations may be present. The degree to which the salts present in these soils are diluted or concentrated must be given careful consideration.
1.7 Since the tests described herein are performed only on that portion of a soil which passes the 425-µpm (No. 40) sieve, the relative contribution of this portion of the soil to the properties of the sample as a whole must be considered when using these tests to evaluate properties of a soil.
1.8 The values stated in acceptable metric units are to be regarded as the standard. The values given in parentheses are for information only.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.