1、Designation: D 5220 02Standard Test Method forWater Content of Soil and Rock In-Place by the NeutronDepth Probe Method1This standard is issued under the fixed designation D 5220; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the calculation of the watercontent of soil and rock by thermalization or slowing of
3、fastneutrons where the neutron source and the thermal neutrondetector are placed at the desired depth in the bored hole linedby an access tube (see Note 1).1.2 The water content, in mass per unit volume of thematerial under test, is calculated by comparing the thermalneutron count rate with previous
4、ly established calibration data(see Annex A1).1.3 A precision statement has not been developed for thisstandard at this time. Therefore, this standard should not beused for acceptance or rejection of a material for purchasingpurposes unless correlated to other accepted ASTM methods.1.4 The values ex
5、pressed in SI units are regarded as thestandard. The inch-pound units given in parentheses may beapproximate and are provided for information only.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 sta
6、ndard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazards aregiven in Section 7.2. Referenced Documents2.1 ASTM Standards:D 1452 Practice for Soil Investigation and Sampling byAuger Borings2D 1586 Method for
7、Penetration Test and Split-Barrel Sam-pling of Soils2D 1587 Practice for Thin Walled Tube Sampling of Soils2D2113 Practice for Diamond Core Drilling for Site Inves-tigation2D 2216 Test Method for Laboratory Determination of Water(Moisture) Content of Soil, Rock, and Soil-AggregateMixtures2D 2937 Tes
8、t Method for Density of Soil in Place by theDrive-Cylinder Method2D 3017 Test Method for Moisture Content of Soil andSoil-Aggregate in Place by Nuclear Methods (ShallowDepth)2D 3550 Practice for Ring-Lined Barrel Sampling of Soils2D 4428/D 4228M Test Method for Crosshole Seismic Test-ing2D 5195 Test
9、 Method for Density of Soil and Rock in Placeat Depths Below the Surface by Nuclear Methods33. Summary of Test Method3.1 This test method uses thermalization of neutron radia-tion to calculate the in-place water content of soil and rock atvarious depths by placing a probe containing a neutron source
10、and a thermal neutron detector at desired depths in a bored holelined by an access tube as opposed to surface measurements inaccordance with Test Method D 3017.3.2 Neutrons emitted by the source are thermalized (slowed)by collisions with materials of low atomic numbers. Hydrog-enous materials, such
11、as water and other compounds contain-ing hydrogen, are most effective in thermalizing neutrons. Inthis apparatus the neutrons thermalized by the material undertest are detected by the thermal neutron detector.3.3 In the absence of interference elements as discussed inSection 5, the number of thermal
12、ized neutrons is a function ofthe hydrogen content of the material under test and the watercontent is proportional to the hydrogen content.3.4 By the use of a calibration process the water content iscalculated by correlating the count rate to known watercontents.4. Significance and Use4.1 This test
13、method is useful as a rapid, nondestructivetechnique for the calculation of the in-place water content ofsoil and rock at desired depths below the surface.4.2 This test method is useful for informational and researchpurposes. It should only be used for quality control andacceptance testing when corr
14、elated to actual water contentsusing procedures and methods described in A1.2.3.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.08 on Special andConstruction Control Tests.Current edition approved Feb. 10, 2002. Pu
15、blished May 2002. Originallypublished as D 522092. Last previous edition D 522092(1997)2Annual Book of ASTM Standards, Vol 04.08.3Annual Book of ASTM Standards, Vol 04.09.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 The non-de
16、structive nature of this test method allowsrepetitive measurements to be made at a single test location forstatistical analysis and to monitor changes over time.4.4 The fundamental assumptions inherent in this testmethod are that the material under test is homogeneous andhydrogen present is in the f
17、orm of water as defined by TestMethod D 2216.5. Interferences5.1 The sample heterogeneity, density, and chemical com-position of the material under test will affect the measurements.The apparatus must be calibrated to the material under test oradjustments made in accordance with Annex A2.5.1.1 Hydro
18、gen, in forms other than water, as defined byTest Method D 2216 and carbon, present in organic soils, willcause measurements in excess of the true water value. Someelements such as boron, chlorine, and minute quantities ofcadmium, if present in the material under test, will causemeasurements lower t
19、han the true water value.5.2 This test method exhibits spatial bias in that it is moresensitive to water contained in the material closest to the accesstube. The measurement is not necessarily an average watercontent of the total sample involved.5.2.1 Voids around the access tube can affect the meas
20、ure-ment (see 11.1.2).5.3 The sample volume is approximately 0.048 m3(1.7 ft3)with a water content of 200 kg/m3(12.5 lbf/ft3). The actualsample volume is indeterminate and varies with the apparatusand the water content of the material. In general, the greater thewater content of the material, the sm
21、aller the volume involvedin the measurement.6. Apparatus (See Fig. 1)6.1 The apparatus shall consist of a nuclear instrumentcapable of measuring water content at various depths below thesurface containing the following:6.1.1 A sealed mixture of a radioactive material such asamericium or radium with
22、a target element such as beryllium,and a suitable thermal neutron detector, and6.1.2 A suitable timed scaler and power source.6.2 The apparatus shall be equipped with a cylindrical probecontaining the neutron source and detector, connected by acable of sufficient design and length, that is capable o
23、f beinglowered down the cased hole to desired test depths.6.3 The apparatus shall be equipped with a reference stan-dard, a fixed shape of hydrogenous material used for checkingapparatus operation and to establish conditions for a reproduc-ible reference count rate. It may also serve as a radiation
24、shield.6.4 Apparatus PrecisionSee Annex A3 for the precisionof the apparatus.6.5 Accessories:6.5.1 Access TubingThe access tubing (casing) is requiredfor all access holes in nonlithified materials (soils and poorlyconsolidated rock) that cannot maintain constant boreholediameter with repeated measur
25、ements. If access tubing isrequired the tubing shall be of a material such as aluminum,steel, or polyvinyl chloride, having an interior diameter largeenough to permit probe access without binding. The tubingshall be as thin-walled as possible to provide close proximity ofthe probe to the material un
26、der test. The same type of tubingshall be used in the field as is used in calibration.6.5.2 Hand auger or power drilling equipment that can beused to establish the access hole. Any drilling equipment thatprovides a suitable clean open hole for installation of accesstubing and insertion of the probe
27、shall be acceptable. Theequipment used shall be capable of maintaining constantborehole diameter to ensure that the measurements are per-formed on undisturbed soil and rock. The type of equipmentand methods of advancing the access hole should be reported.6.5.3 Dummy ProbeA cylindrical probe the same
28、 size asthe probe containing the neutron source and a chain or cable ofsufficient design and length to permit lowering the dummyprobe down the cased hole to desired test depths.7. Hazards7.1 This equipment utilizes radioactive materials that maybe hazardous to the health of the users unless proper p
29、recau-tions are taken. Users of this equipment must become com-pletely familiar with possible safety hazards and with allapplicable regulations concerning the handling and use ofradioactive materials. Effective user instructions together withroutine safety procedures are a recommended part of theope
30、ration of this apparatus.8. Calibration, Standardization, and Reference Check8.1 Calibrate the instrument in accordance with Annex A1.8.2 Adjust the calibration in accordance with Annex A2 ifadjustments are necessary.8.3 Standardization and Reference Check:FIG. 1 Schematic Diagram; Water Content by
31、Neutron DepthProbe MethodD 5220 0228.3.1 Nuclear apparatus are subject to the long-term decayof the radioactive source and aging of detectors and electronicsystem, that may change the relationship between count rateand water content. To offset these changes, the apparatus maybe calibrated as the rat
32、io of the measurement count rate to acount rate made on a reference standard. The reference countrate should be in the same or a higher order of magnitude thanthe range of measurement count rates over the useful watercontent range of the apparatus.8.3.2 Standardization of equipment should be perform
33、ed atthe start of each days work and a permanent record of thesedata retained. Perform the standardization with the apparatuslocated at least 10 m (30 ft) away from other apparatuscontaining neutron emitting radioactive sources and clear oflarge masses of water or other items which may affect theref
34、erence count rate.8.3.2.1 If recommended by the apparatus manufacturer toprovide more stable and consistent results: turn on the appa-ratus prior to use to allow it to stabilize; and leave the poweron during the days testing.8.3.2.2 Using the reference standard, take at least fourrepetitive readings
35、 at the manufacturers recommended mea-surement period and determine the mean. If available on theapparatus, one measurement at a period of four or more timesthe recommended period is acceptable. These measurementsconstitute one standardization check.8.3.2.3 If the value obtained above is within the
36、limits statedbelow, the equipment is considered to be in satisfactorycondition and the value may be used to determine the countratios for the day of use. If the value is outside these limits,allow additional time for the apparatus to stabilize, make surethe area is clear of sources of interference a
37、nd then conductanother standardization check. If the second standardizationcheck is within the limits, the apparatus may be used, but if italso fails the test, the apparatus shall be adjusted or repaired asrecommended by the manufacturer. The limits are as follows:Ns,5No12.0=No=FandNs.5No22.0=No=Fwh
38、ere:Ns= value of current standardization check,No= average of the past four values of Nstaken previously,andF = value of prescale.NOTE 1Some instruments have built-in provisions to compute anddisplay the results of a statistical test of the standardization counts and toindicate if the apparatus is i
39、n satisfactory condition.8.3.3 Use the value of Nsto determine the count ratios forthe current days use of the apparatus. If, for any reason, themeasured water content becomes suspect during the days use,perform another standardization check.8.3.4 If the instrument was calibrated in the field usingm
40、ethods described in Annex A1.2.3 the count rate on any trialreading may be adjusted by a correction factor determined ininitial calibration.9. Procedure9.1 Installation of Access Tubing (Casing):9.1.1 Drill the access tube hole and install access tubing ina manner dependent upon the material to be t
41、ested, the depth tobe tested, and the available drilling equipment.9.1.2 The access hole must be clear enough to allowinstalling the tubing yet must provide a snug fit. Voids alongthe sides of the tubing may cause erroneous readings.9.1.2.1 If voids are suspected to be caused by the drillingprocess
42、they can be grouted using procedures in Test MethodD 4428.9.1.2.2 The only method to determine the presence of voidsis to perform field calibrations provided in Annex A2.2.3.9.1.3 Record and note the position of the ground watertable, perched water tables, and changes in strata as drillingprogresses
43、.9.1.3.1 If ground water is encountered or saturated condi-tions are expected to develop, seal the tube at the bottom toprevent water seepage into the tube using procedures given inTest Method D 4428 or the manufacturers recommendedprocedures. This will prevent erroneous readings and possibledamage
44、to the probe.9.1.4 The tubing should project above the ground and becapped to prevent foreign material from entering. The accesstube should not project above the ground so high that it mightbe damaged by equipment passing over it.9.1.4.1 Install all tubes at the same height above the groundas this e
45、nables marking the cable to indicate the measureddepth to be used for all tubes.9.2 Lower a dummy probe down the access tube to verifyproper clearance before lowering the probe containing theradioactive source.9.3 Standardize the apparatus.9.4 Proceed with the test as follows:9.4.1 Seat the apparatu
46、s firmly over the access tube, thenlower the probe into the tube to the desired depth. Secure theprobe by cable clamps (usually provided by the apparatusmanufacturer).9.4.2 Take a measurement count at the selected timingperiod.NOTE 2The above procedure is performed in an installed access tubethat wi
47、ll allow repeated in-place measurements. In some field situations itmay be more appropriate to use a drilling technique involving alternatingbefore access tubing and one of the following: a large diameter hollowstem auger, a split-spoon sampler, or a thin-walled volumetric sampler.This technique is
48、destructive and only one measurement can be made ateach depth per hole.10. Interpretation10.1 Determine the ratio of the reading obtained comparedto the standard count. Then using the calibration data combinedwith appropriate calibration adjustments, or apparatus directreadout features, calculate th
49、e water content in mass per unitvolume of the material under test.NOTE 3Some instruments have built-in provisions to compute anddisplay the ratio and corrected water content per unit volume.D 5220 02310.2 If water content as a percentage of dry density isrequired, the in-place density may be determined by usingeither the same apparatus or a different apparatus that deter-mines density at depths below the surface by the nuclearmethod (see Test Method D 5195) or by a method such asdensity determination of soil in-place by the drive-cylindermethod (see Test Method D 2937).11
