Standard Test Method for Unconfined Compressive Strength of Cohesive Soil

SIGNIFICANCE AND USE
The primary purpose of the unconfined compression test is to quickly obtain a measure of compressive strength for those soils that possess sufficient cohesion to permit testing in the unconfined state.
Samples of soils having slickensided or fissured structure, samples of some types of loess, very soft clays, dry and crumbly soils and varved materials, or samples containing significant portions of silt or sand, or both (all of which usually exhibit cohesive properties), frequently display higher shear strengths when tested in accordance with Test Method D 2850. Also, unsaturated soils will usually exhibit different shear strengths when tested in accordance with Test Method D 2850.
If tests on the same sample in both its intact and remolded states are performed, the sensitivity of the material can be determined. This method of determining sensitivity is suitable only for soils that can retain a stable specimen shape in the remolded state.
Note 2—For soils that will not retain a stable shape, a vane shear test or Test Method D 2850 can be used to determine sensitivity.
Note 3—The quality of the result produced by this standard 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 D 3740 are generally considered capable of competent and objective testing/sampling/inspection. Users of this standard are cautioned that compliance with Practice D 3740 does not in itself ensure reliable results. Reliable results depend on many factors; Practice D 3740 provides a means of evaluating some of those factors.
SCOPE
1.1 This test method covers the determination of the unconfined compressive strength of cohesive soil in the intact, remolded, or reconstituted condition, using strain-controlled application of the axial load.
1.2 This test method provides an approximate value of the strength of cohesive soils in terms of total stresses.
1.3 This test method is applicable only to cohesive materials which will not expel or bleed water (water expelled from the soil due to deformation or compaction) during the loading portion of the test and which will retain intrinsic strength after removal of confining pressures, such as clays or cemented soils. Dry and crumbly soils, fissured or varved materials, silts, peats, and sands cannot be tested with this method to obtain valid unconfined compression strength values. Note 1
The determination of the unconsolidated, undrained strength of cohesive soils with lateral confinement is covered by Test Method D 2850.
1.4 This test method is not a substitute for Test Method D 2850.
1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D 6026.
1.5.1 The procedures used to specify how data are collected/recorded and calculated in this test method are regarded as the industry standard. In addition, they are representative of the significant digits that should generally be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user's objectives; and it is common practice to increase or reduce significant digits of reported data to commensurate with these considerations. It is beyond the scope of this test method to consider significant digits used in analysis methods for engineering design.
1.6 The values stated in SI units are to be regarded as the standard. The values stated in inch-pound units are approximate.
This standard does not purport to address all of the safety problems, 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.

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ASTM D2166-06 - Standard Test Method for Unconfined Compressive Strength of Cohesive Soil
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D2166 −06
StandardTest Method for
1
Unconfined Compressive Strength of Cohesive Soil
This standard is issued under the fixed designation D2166; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 1.6 The values stated in SI units are to be regarded as the
standard. The values stated in inch-pound units are approxi-
1.1 This test method covers the determination of the uncon-
mate.
fined compressive strength of cohesive soil in the intact,
1.7 This standard does not purport to address all of the
remolded, or reconstituted condition, using strain-controlled
safety problems, if any, associated with its use. It is the
application of the axial load.
responsibility of the user of this standard to establish appro-
1.2 This test method provides an approximate value of the
priate safety and health practices and determine the applica-
strength of cohesive soils in terms of total stresses.
bility of regulatory limitations prior to use.
1.3 Thistestmethodisapplicableonlytocohesivematerials
2. Referenced Documents
which will not expel or bleed water (water expelled from the
2
soil due to deformation or compaction) during the loading 2.1 ASTM Standards:
portion of the test and which will retain intrinsic strength after D653 Terminology Relating to Soil, Rock, and Contained
removal of confining pressures, such as clays or cemented Fluids
D854 Test Methods for Specific Gravity of Soil Solids by
soils. Dry and crumbly soils, fissured or varved materials, silts,
peats, and sands cannot be tested with this method to obtain Water Pycnometer
D1587 Practice for Thin-Walled Tube Sampling of Soils for
valid unconfined compression strength values.
Geotechnical Purposes
NOTE 1—The determination of the unconsolidated, undrained strength
D2216 Test Methods for Laboratory Determination of Water
of cohesive soils with lateral confinement is covered by Test Method
(Moisture) Content of Soil and Rock by Mass
D2850.
D2488 Practice for Description and Identification of Soils
1.4 This test method is not a substitute for Test Method
(Visual-Manual Procedure)
D2850.
D2850 Test Method for Unconsolidated-Undrained Triaxial
Compression Test on Cohesive Soils
1.5 All observed and calculated values shall conform to the
D3740 Practice for Minimum Requirements for Agencies
guidelines for significant digits and rounding established in
Engaged in Testing and/or Inspection of Soil and Rock as
Practice D6026.
Used in Engineering Design and Construction
1.5.1 Theproceduresusedtospecifyhowdataarecollected/
D4220 Practices for Preserving and Transporting Soil
recorded and calculated in this test method are regarded as the
Samples
industry standard. In addition, they are representative of the
D4318 Test Methods for Liquid Limit, Plastic Limit, and
significant digits that should generally be retained. The proce-
Plasticity Index of Soils
dures used do not consider material variation, purpose for
D6026 Practice for Using Significant Digits in Geotechnical
obtaining the data, special purpose studies, or any consider-
Data
ations for the user’s objectives; and it is common practice to
D6913 Test Methods for Particle-Size Distribution (Grada-
increase or reduce significant digits of reported data to com-
tion) of Soils Using Sieve Analysis
mensurate with these considerations. It is beyond the scope of
E177 Practice for Use of the Terms Precision and Bias in
this test method to consider significant digits used in analysis
ASTM Test Methods
methods for engineering design.
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.05 on Strength and
2
Compressibility of Soils. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 15, 2006. Published January 2007. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
e1
approved in 1963. Last previous edition approved in 2000 as D2166 – 00 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D2166-06. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D2166−06
3. Terminology travelinwhichthesampleenteredthetube,andwithnegligible
disturbance of the sample. Conditions at the time of sample
3.1 Definitions—Refer to Terminolo
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