ASTM D2487-17e1
(Practice)Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
SIGNIFICANCE AND USE
5.1 This standard classifies soils from any geographic location into categories representing the results of prescribed laboratory tests to determine the particle-size characteristics, the liquid limit, and the plasticity index.
5.2 The assigning of a group name and symbol(s) along with the descriptive information required in Practice D2488 can be used to describe a soil to aid in the evaluation of its significant properties for engineering use.
5.3 The various groupings of this classification system have been devised to correlate in a general way with the engineering behavior of soils. This standard provides a useful first step in any field or laboratory investigation for geotechnical engineering purposes.
5.4 This standard may also be used as an aid in training personnel in the use of Practice D2488.
5.5 This standard may be used in combination with Practice D4083 when working with frozen soils.
Note 5: Notwithstanding the statements on precision and bias contained in this standard: The precision of this test method is dependent on the competence of the personnel performing it and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice D3740 does not in itself assure reliable testing. Reliable testing depends on several factors; Practice D3740 provides a means for evaluating some of those factors.
SCOPE
1.1 This practice describes a system for classifying mineral and organo-mineral soils for engineering purposes based on laboratory determination of particle-size characteristics, liquid limit, and plasticity index and shall be used when precise classification is required.
Note 1: Use of this standard will result in a single classification group symbol and group name except when a soil contains 5 to 12 % fines or when the plot of the liquid limit and plasticity index values falls into the crosshatched area of the plasticity chart. In these two cases, a dual symbol is used, for example, GP-GM, CL-ML. When the laboratory test results indicate that the soil is close to another soil classification group, the borderline condition can be indicated with two symbols separated by a slash. The first symbol should be the one based on this standard, for example, CL/CH, GM/SM, SC/CL. Borderline symbols are particularly useful when the liquid limit value of clayey soils is close to 50. These soils can have expansive characteristics and the use of a borderline symbol (CL/CH, CH/CL) will alert the user of the assigned classifications of expansive potential.
1.2 The group symbol portion of this system is based on laboratory tests performed on the portion of a soil sample passing the 3-in. (75-mm) sieve (see Specification E11).
1.3 As a classification system, this standard is limited to naturally occurring soils.
Note 2: The group names and symbols used in this test method may be used as a descriptive system applied to such materials as shale, claystone, shells, crushed rock, etc. See Appendix X2.
1.4 This standard is for qualitative application only.
Note 3: When quantitative information is required for detailed designs of important structures, this test method must be supplemented by laboratory tests or other quantitative data to determine performance characteristics under expected field conditions.
1.5 This standard is the ASTM version of the Unified Soil Classification System. The basis for the classification scheme is the Airfield Classification System developed by A. Casagrande in the early 1940s.2 It became known as the Unified Soil Classification System when several U.S. Government Agencies adopted a modified version of the Airfield System in 1952.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of...
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´1
Designation:D2487 −17
Standard Practice for
Classification of Soils for Engineering Purposes (Unified
1
Soil Classification System)
This standard is issued under the fixed designation D2487; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1
ε NOTE—Footnote L in Table 1 was editorially corrected in April 2020.
1. Scope* is the Airfield Classification System developed by A. Casa-
2
grande in the early 1940s. It became known as the Unified
1.1 This practice describes a system for classifying mineral
Soil Classification System when several U.S. Government
and organo-mineral soils for engineering purposes based on
Agencies adopted a modified version of theAirfield System in
laboratory determination of particle-size characteristics, liquid
1952.
limit, and plasticity index and shall be used when precise
1.6 This standard does not purport to address all of the
classification is required.
safety concerns, if any, associated with its use. It is the
NOTE 1—Use of this standard will result in a single classification group
responsibility of the user of this standard to establish appro-
symbol and group name except when a soil contains 5 to 12% fines or
priate safety, health, and environmental practices and deter-
when the plot of the liquid limit and plasticity index values falls into the
crosshatchedareaoftheplasticitychart.Inthesetwocases,adualsymbol mine the applicability of regulatory limitations prior to use.
is used, for example, GP-GM, CL-ML. When the laboratory test results
1.7 This practice offers a set of instructions for performing
indicate that the soil is close to another soil classification group, the
one or more specific operations. This document cannot replace
borderline condition can be indicated with two symbols separated by a
education or experience and should be used in conjunction
slash. The first symbol should be the one based on this standard, for
withprofessionaljudgment.Notallaspectsofthispracticemay
example, CL/CH, GM/SM, SC/CL. Borderline symbols are particularly
usefulwhentheliquidlimitvalueofclayeysoilsiscloseto50.Thesesoils
be applicable in all circumstances. This ASTM standard is not
can have expansive characteristics and the use of a borderline symbol
intended to represent or replace the standard of care by which
(CL/CH, CH/CL) will alert the user of the assigned classifications of
the adequacy of a given professional service must be judged,
expansive potential.
nor should this document be applied without consideration of
1.2 The group symbol portion of this system is based on
a project’s many unique aspects. The word “Standard” in the
laboratory tests performed on the portion of a soil sample
title of this document means only that the document has been
passing the 3-in. (75-mm) sieve (see Specification E11).
approved through the ASTM consensus process.
1.3 As a classification system, this standard is limited to
1.8 This international standard was developed in accor-
naturally occurring soils.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
NOTE 2—The group names and symbols used in this test method may
Development of International Standards, Guides and Recom-
be used as a descriptive system applied to such materials as shale,
claystone, shells, crushed rock, etc. See Appendix X2.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.4 This standard is for qualitative application only.
NOTE3—Whenquantitativeinformationisrequiredfordetaileddesigns
2. Referenced Documents
of important structures, this test method must be supplemented by
3
laboratory tests or other quantitative data to determine performance
2.1 ASTM Standards:
characteristics under expected field conditions.
C117Test Method for Materials Finer than 75-µm (No. 200)
1.5 This standard is the ASTM version of the Unified Soil Sieve in Mineral Aggregates by Washing
Classification System. The basis for the classification scheme
1 2
This practice is under the jurisdiction of ASTM Committee D18 on Soil and Casagrande, A., “Classification and Identification of Soils,” Transactions,
Rock and is the direct responsibility of Subcommittee D18.07 on Identification and ASCE, 1948 , p. 901.
3
Classification of Soils. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition a
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