ASTM D6836-02
(Test Method)Standard Test Methods for Determination of the Soil Water Chararcteristic Curve for Desorption Using a Hanging Column, Pressure Extractor, Chilled Mirror Hygrometer, and/or Centrifuge
Standard Test Methods for Determination of the Soil Water Chararcteristic Curve for Desorption Using a Hanging Column, Pressure Extractor, Chilled Mirror Hygrometer, and/or Centrifuge
SIGNIFICANCE AND USE
The soil water characteristic curve (SWCC) is fundamental to hydrological characterization of unsaturated soils and is required for most analyses of water movement in unsaturated soils. The SWCC is also used in characterizing the shear strength and compressibility of unsaturated soils. The unsaturated hydraulic conductivity of soil is often estimated using properties of the SWCC and the saturated hydraulic conductivity.
This method applies only to soils containing two pore fluids: a gas and a liquid. The liquid is usually water and the gas is usually air. Other liquids may also be used, but caution must be exercised if the liquid being used causes excessive shrinkage or swelling of the soil matrix.
A full investigation has not been conducted regarding the correlation between soil water characteristic curves obtained using this method and soil water characteristics curves of in-place materials. Thus, results obtained from this method should be applied to field situations with caution and by qualified personnel.
Note 1—The quality of the result produced by this standard depends on the competence of the personnel performing the test 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, etc. 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 these factors.
SCOPE
1.1 This test method covers the determination of soil water characteristic curves (SWCCs) for desorption (drying). SWCCs describe the relationship between suction and volumetric water content, gravimetric water content, or degree of water saturation. SWCCs are also referred to as soil water retention curves, soil water release curves, or capillary pressure curves.
1.2 This standard describes five methods (A-E) for determining the soil water characteristic curve. Method A (hanging column) is suitable for making determinations for suctions in the range of 0 to 80 kPa. Method B (pressure chamber with volumetric measurement) and Method C (pressure chamber with gravimetric measurement) are suitable for suctions in the range of 0 to 1500 kPa. Method D (chilled mirror hygrometer) is suitable for making determinations for suctions in the range of 500 kPa to 100 MPa. Method E (centrifuge method) is suitable for making determinations in the range 0 to 120 kPa. Method A typically is used for coarse soils with little fines that drain readily. Methods B and C typically are used for finer soils which retain water more tightly. Method D is used when suctions near saturation are not required and commonly is employed to define the dry end of the soil water characteristic curve (that is, water contents corresponding to suctions > 1000 kPa). Method E is typically used for coarser soils where an appreciable amount of water can be extracted with suctions up to 120 kPa. The methods may be combined to provide a detailed description of the soil water characteristic curve. In this application, Method A or E is used to define the soil water characteristic curve at lower suctions (0 to 80 kPa for A, 0 to 120 kPa for E) near saturation and to accurately identify the air entry suction, Method B or C is used to define the soil water characteristic curve for intermediate water contents and suctions (100 to 1000 kPa), and Method D is used to define the soil water characteristic curves at low water contents and higher suctions (> 1000 kPa) and
1.3 All observed and calculated values shall conform to the guide for significant digits and rounding established in Practice D 6026. The procedures in Practice D 6026 that are used to specify how data are collected, recorded, and calculated are regarded as the industry standard. In addition, they are representative o...
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Designation: D 6836 – 02
Standard Test Methods for
Determination of the Soil Water Characteristic Curve for
Desorption Using a Hanging Column, Pressure Extractor,
1
Chilled Mirror Hygrometer, and/or Centrifuge
This standard is issued under the fixed designation D6836; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.3 All observed and calculated values shall conform to the
guideforsignificantdigitsandroundingestablishedinPractice
1.1 This test method covers the determination of soil water
D6026. The procedures in Practice D6026 that are used to
characteristic curves (SWCCs) for desorption (drying).
specify how data are collected, recorded, and calculated are
SWCCs describe the relationship between suction and volu-
regarded as the industry standard. In addition, they are repre-
metric water content, gravimetric water content, or degree of
sentative of the significant digits that should generally be
water saturation. SWCCs are also referred to as soil water
retained. The procedures do not consider material variation,
retentioncurves,soilwaterreleasecurves,orcapillarypressure
purpose for obtaining the data, special purpose studies, or any
curves.
considerations for the objectives of the user. Increasing or
1.2 This standard describes five methods (A-E) for deter-
reducing the significant digits of reported data to be commen-
mining the soil water characteristic curve. MethodA(hanging
surate with these considerations is common practice. Consid-
column) is suitable for making determinations for suctions in
eration of the significant digits to be used in analysis methods
the range of 0 to 80 kPa. Method B (pressure chamber with
for engineering design is beyond the scope of this standard.
volumetric measurement) and Method C (pressure chamber
1.4 This standard does not purport to address all of the
with gravimetric measurement) are suitable for suctions in the
safety concerns, if any, associated with its use. It is the
range of 0 to 1500 kPa. Method D (chilled mirror hygrometer)
responsibility of the user of this standard to establish appro-
is suitable for making determinations for suctions in the range
priate safety and health practices and determine the applica-
of 500 kPa to 100 MPa. Method E (centrifuge method) is
bility of regulatory limitations prior to use.
suitable for making determinations in the range 0 to 120 kPa.
MethodAtypically is used for coarse soils with little fines that
2. Referenced Documents
drainreadily.MethodsBandCtypicallyareusedforfinersoils
2.1 ASTM Standards:
which retain water more tightly. Method D is used when
D421 Practice for Dry Preparation of Soil Samples for
suctions near saturation are not required and commonly is
2
Particle-SizeAnalysisandDeterminationofSoilContents
employed to define the dry end of the soil water characteristic
D425 Test Method for Centrifuge Moisture Equivalent of
curve(thatis,watercontentscorrespondingtosuctions>1000
2
Soils
kPa). Method E is typically used for coarser soils where an
D653 Terminology Relating to Soil, Rock, and Contained
appreciable amount of water can be extracted with suctions up
2
Fluids
to 120 kPa. The methods may be combined to provide a
D698 Test Method for Laboratory Compaction Character-
detailed description of the soil water characteristic curve. In
3
2
istics of Soil Using Standard Effort [600 kN-mJ/m ]
this application, MethodAor E is used to define the soil water
2
D854 Test Method for Specific Gravity of Soils
characteristic curve at lower suctions (0 to 80 kPa for A, 0 to
D2216 Method for Laboratory Determination of Water
120kPaforE)nearsaturationandtoaccuratelyidentifytheair
(Moisture) Content of Soil, Rock, and Soil-Aggregate
entry suction, Method B or C is used to define the soil water
2
Mixtures
characteristic curve for intermediate water contents and suc-
D3740 Practice for Minimum Requirements for Agencies
tions(100to1000kPa),andMethodDisusedtodefinethesoil
Engaged in theTesting and/or Inspection of Soil and Rock
water characteristic curves at low water contents and higher
2
as Used in Engineering Design and Construction
suctions (> 1000 kPa) and
D4753 Practice for Minimum Requirements for Agencies
Engaged in theTesting and/or Inspection of Soil and Rock
2
as Used in Engineering Design and Construction
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.04 on Hydrologic
Properties and Hydraulic Barriers.
2
Current edition approved Nov. 10, 2002. Published February 2003. Annual Book of ASTM Standards, Vol 04.08.
Copyright © ASTM International, 10
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