1、Designation: D5298 10Standard Test Method forMeasurement of Soil Potential (Suction) Using Filter Paper1This standard is issued under the fixed designation D5298; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers laboratory filter papers aspassive sensors to evaluate the soil matric (matrix) and totalpotential (su
3、ction), a measure of the free energy of thepore-water or tension stress exerted on the pore-water by thesoil matrix (1, 2).2The term potential or suction is descriptiveof the energy status of soil water.1.2 This test method controls the variables for measurementof the water content of filter paper t
4、hat is in direct contact withsoil or in equilibrium with the partial pressure of water vaporin the air of an airtight container enclosing a soil specimen. Thefilter paper is enclosed with a soil specimen in the airtightcontainer until moisture equilibrium is established; that is, thepartial pressure
5、 of water vapor in the air is in equilibrium withthe vapor pressure of pore-water in the soil specimen.1.3 This test method provides a procedure for calibratingdifferent types of filter paper for use in evaluating soil matricand total potential.1.4 The values stated in SI units are to be regarded as
6、standard. The inch-pound units given in parentheses areapproximate.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the ap
7、plica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C114 Test Methods for Chemical Analysis of HydraulicCementD653 Terminology Relating to Soil, Rock, and ContainedFluidsD1125 Test Methods for Electrical Conductivity and Resis-tivity of WaterD2216 Test Meth
8、ods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4542 Test Method for Pore Water Extraction and Deter-mination
9、of the Soluble Salt Content of Soils by Refrac-tometerD4753 Guide for Evaluating, Selecting, and SpecifyingBalances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD6836 Test Methods for Determination of the Soil WaterCharacteristic Curve for Desorption Using Hanging Col-
10、umn, Pressure Extractor, Chilled Mirror Hygrometer, orCentrifugeE1 Specification for ASTM Liquid-in-Glass ThermometersE337 Test Method for Measuring Humidity with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)E832 Specification for Laboratory Filter PapersE1137/E1137M Specifica
11、tion for Industrial Platinum Resis-tance ThermometersE2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard Precision Liquids3. Terminology3.1 Definitions:3.1.1 For common definitions of technical terms in thisstandard, refer to Terminology D653.3.2 Definitions of Terms Specific
12、to This Standard:3.2.1 atmospherea unit of pressure equal to 76 cm Mer-cury or 101 kPa at 0 C.3.2.2 matric (matrix) suction, hm (kPa)the negative pres-sure (expressed as a positive value), relative to ambientatmospheric pressure on the soil water, to which a solutionidentical in composition with the
13、 soil water must be subjectedin order to be in equilibrium through a porous permeable wallwith the soil water; pressure equivalent to that measured byTest Methods D6836. Matric suction is a function of the1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the dir
14、ect responsibility of Subcommittee D18.04 on HydrologicProperties and Hydraulic Barriers.Current edition approved July 1, 2010. Published August 2010. Originallyapproved in 1992. Discontinued December 2002 and reinstated as D529803. Lastprevious edition approved in 2003 as D529803. DOI: 10.1520/D529
15、8-10.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Doc
16、ument Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.relative humidity due to the difference in air and water pressureacross the water surface; the relative humidity or water vaporpressure decreases a
17、s the radius of curvature of the watersurface decreases. The term “matric” is grammatically correct,while matrix is commonly used in the civil engineeringliterature.3.2.3 molality, moles/1000 gnumber of moles of soluteper 1000 g of solvent.3.2.4 molemolecular weight of a substance in grams.3.2.5 osm
18、otic (solute) suction, hs (kPa)the negative pres-sure to which a pool of pure water must be subjected in orderto be in equilibrium through a semipermeable membrane witha pool containing a solution identical in composition with thesoil water; decrease in relative humidity due to the presence ofdissol
19、ved salts in pore-water.3.2.6 pFa unit of negative pressure expressed as thelogarithm to the base ten of the height in centimeters that acolumn of water will rise by capillary action or negative gaugepressure (kPa) divided by the unit weight of water (kN/m3)times 1000. pF 3 + logarithm to the base t
20、en of the negativepressure in atmospheres. Refer to capillary head or capillaryrise in Terminology D653.3.2.7 soil relative humidity, Rhthe ratio of the vaporpressure of pore water in the soil to the vapor pressure of freepure water. Relative humidity in the soil is defined as relativehumidity measu
21、red by Test Method E337.3.2.8 total potential (kPa)the sum of gravitational, pres-sure, osmotic and external gas potentials. Potential may beidentified with suction when gravitational and external gaspotentials are neglected.3.2.9 total soil suction, h (kPa)the negative pressure,relative to the exte
22、rnal gas pressure on the soil water, to whicha pool of pure water must be subjected to be in equilibriumwith the soil water through a semipermeable membrane that ispermeable to water molecules only. Total soil suction (ex-pressed as a positive value) is the sum of osmotic (solute) andmatric (matrix)
23、 suctions.3.2.10 vapor pressure of free pure water (kPa)the satura-tion vapor pressure of free pure water at a given dry-bulbtemperature.3.2.11 vapor pressure of pore water in soil (kPa)thepartial pressure of water vapor that is in equilibrium withpore-water in soil at a given dry-bulb temperature.4
24、. Summary of Test Method4.1 Filter papers are placed in an airtight container with aspecimen for seven days to allow sufficient time for the vaporpressure of pore-water in the specimen, vapor pressure of porewater in the filter paper, and partial vapor pressure of water inthe air inside the containe
25、r to reach equilibrium. The mass ofthe filter papers is subsequently determined and the suction ofthe specimen is determined from a calibration relationship ofthe filter paper water content with suction applicable to the typeof filter paper and the test procedure of this test method.5. Significance
26、and Use5.1 Soil suction is a measure of the free energy of thepore-water in a soil. Soil suction in practical terms is a measureof the affinity of soil to retain water and can provide informa-tion on soil parameters that are influenced by the soil water; forexample, volume change, deformation, and s
27、trength character-istics of the soil.5.2 Soil suction is related with soil water content throughwater retention characteristic curves (see Test MethodsD6836). Soil water content may be found from Test MethodD2216.5.3 Measurements of soil suction may be used with othersoil and environmental parameter
28、s to evaluate hydrologicprocesses (1) and to evaluate the potential for heave orshrinkage, shear strength, modulus, in situ stress and hydraulicconductivity of unsaturated soils.5.4 The filter paper method of evaluating suction is simpleand economical with a range from 10 to 100 000 kPa (0.1 to1000
29、bars).NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing/s
30、ampling/inspection/etc. Users of this standard arecautioned that compliance with Practice D3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D3740provides a means of evaluating some of those factors.6. Apparatus6.1 Filter PaperThe paper used must be as
31、h-free quanti-tative Type II filter paper, see Specification E832; for example,Whatman No. 42, Fisherbrand 9-790A,4Schleicher andSchuell No. 589 White Ribbon.4A suitable diameter is 5.5 cm(2.2 in.).NOTE 2Filter papers may be treated by dipping each paper in a 2 %concentration of formaldehyde prior t
32、o use to prevent organism growth onor biological decomposition of the filter paper. Biological decompositionmay be significant when filter papers are subject to a moist, warmenvironment for more than 14 days. Appropriate precautions should betaken when preparing formaldehyde solutions and treating f
33、ilter paper.6.2 Specimen Container120 to 240 mL (4 to 8 oz)capacity metal or glass (rust free) container and lid (forexample, coated with zinc chromate to retard rusting) tocontain the specimen and filter papers. The inside of thesecontainers may also be coated with wax to retard rusting.6.3 Filter
34、Paper ContainerThis container holds filterpaper following the equilibration of suction and removal fromthe specimen container.6.3.1 Metal Container AlternateTwo nominal 70 mL (2oz) capacity metal moisture containers (aluminum or stainless)with lids to dry the filter paper. The containers should benu
35、mbered by imprinting with a metal stamp. The containersshould not be written on with any type of marker or labelled inany manner. Throw-away vinyl surgical non-powdered orsimilar gloves should be used anytime the small containersdesignated for filter paper measurements are handled to preventbody oil
36、s from influencing any mass measurements made priorto handling.4The sole source of supply of the apparatus known to the committee at this timeis Thomas Scientific Supply, P.O. Box 99, Swedesboro, NJ 08085. If you are awareof alternative suppliers, please provide this information to ASTM Internationa
37、lHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.D5298 1026.3.2 Plastic Bag AlternatePlastic bag large enough toaccommodate the filter paper disks (approximately 50 mm indimension) capable of an airtight seal.6.4
38、 Insulated ChestAbox of approximately 0.03 m3(1 ft3)capacity insulated with foamed polystyrene or other materialcapable of maintaining temperature within 6 1 C whenexternal temperatures vary 6 3 C.6.5 BalanceA balance or scale having a minimum capac-ity of 20 g and meeting the requirements of 4.2.1.
39、1 ofSpecification C114 for a balance of 0.0001 g readability. Inaddition, balances for performance of Test Method D2216,meeting requirements of Specification D4753.6.6 Drying OvenThermostatically-controlled, preferablyof the forced-draft type, and capable of maintaining a uniformtemperature of 110 6
40、 5 C throughout the drying chamber andmeeting requirements of Test Method D2216.6.7 Metal BlockA metal block 500 g mass with a flatsurface to hasten cooling of the metal containers with filterpaper.6.8 ThermometerAn instrument to determine the tem-perature of the tested soil to an accuracy of 6 1Cin
41、accordance with E1, E1137/E1137M,orE2251.6.9 Miscellaneous EquipmentTweezers, trimming knife,flexible plastic electrical tape, O-rings, screen wire, brass discs,etc. Tweezers should be at least 110 mm (4.5 in.) in length.6.10 DesiccatorA desiccator jar of suitable size contain-ing silica gel or anhy
42、drous calcium sulfate.NOTE 3Anhydrous calcium sulfate is sold under the trade nameDrierite.NOTE 4It is preferable to use a desiccant that changes color toindicate when it needs reconstitution.7. Calibration7.1 Obtain a calibration curve applicable to a specific filterpaper by following the procedure
43、 in Section 8, except forreplacing the soil specimen with salt solutions such as reagentgrade potassium chloride or sodium chloride of known mola-lity in distilled water.7.1.1 Suspend the filter paper above at least 50 cc of a saltsolution in the specimen container, see 6.2, by placing it on animpro
44、vised platform made of inert material such as plastictubing or stainless steel screen.7.1.2 Calculate the suction of the filter paper from therelative humidity of the air above the solution by:h 5RTv ln Rh(1)where:h = suction, kPa,R = ideal gas constant, 8.31432 Joules/moleK,T = absolute temperature
45、, degrees kelvin (K),v = volume of 1000 moles of liquid water, 0.018 m3, andRh= relative humidity, fraction.7.1.3 Standard critical tables may be used to evaluate therelative humidity of water in equilibrium with the salt solutionas illustrated in Table 1. Refer to Test Method E337 for furtherinform
46、ation on relative humidity.7.2 Typical calibration curves for filter papers (for example,Whatman No. 42,4Schleicher and Schuell No. 589),4see Fig.1, consists of two parts. The upper segment represents moistureretained as films adsorbed to particle surfaces, while the lowersegment represents moisture
47、 retained by capillary or surfacetension forces between particles. The filter paper water contentbreak point is wf= 45.3 percent for Whatman No. 42 (3, 4)4and wf= 54 % for Schleicher and Schuell No. 589 (2, 4).47.3 The calibration curves in Fig. 1 are applicable to totalsuction.3Variability in resul
48、ts is less than 2 % of the suctionabove 100 kPa. Soil disturbance has minimal influence onsuction above 20 kPa. At moisture contents with suctions lessthan 20 kPa, sample disturbance increases variability of mea-surement (2, 4). The right vertical axis of Fig. 1 provides thesuction in units pF and a
49、tmospheres pressure; for example, h= 2 log atmospheres is a suction of 100 atmospheres, while pF= 5 or 100 000 cm water.NOTE 5Filter paper may be calibrated by using the pressure mem-brane, see Test Methods D6836 for the range 100 to 1500 kPa (1 to 15atm), and the ceramic plate, see Test Methods D6836 for the range 10 to100 kPa (0.1 to 1 atm).8. Procedure8.1 Filter Paper PreparationDry filter papers selected fortesting at least 16 h or overnight in the drying oven. Place filterpapers in a desiccant jar over desiccant after drying for storageunti
