1、Standard Method of Test for In-Place Density and Moisture Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth) AASHTO Designation: T 310-13 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS 1b T 310-
2、1 AASHTO Standard Method of Test for In-Place Density and Moisture Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth) AASHTO Designation: T 310-13 1. SCOPE 1.1. This test method describes the procedure for determining the in-place density and moisture of soil and soil-aggregate by
3、 use of nuclear gauge. The density of the material may be determined by either Direct Transmission, Backscatter, or Backscatter/Air-Gap Ratio Method. The moisture of the material is determined only from measurements taken at the surface of the soil (i.e., backscatter). 1.2. DensityThe total or wet d
4、ensity of soil and soil-rock mixtures is determined by the attenuation of gamma radiation where the source or detector is placed at a known depth up to 300 mm (12 in.) while the detector(s) or source remains on the surface (Direct Transmission Method) or the source and detector(s) remain on the surf
5、ace (Backscatter Method). 1.2.1. The density in mass per unit volume of the material under test is determined by comparing the detected rate of gamma radiation with previously established calibration data. 1.3. MoistureThe moisture content of the soil and soil-rock mixtures is determined by thermali
6、zation or slowing of fast neutrons where the neutron source and the thermal neutron detector both remain at the surface. 1.3.1. The water content in mass per unit volume of the material under test is determined by comparing the detection rate of thermalized or slow neutrons with previously establish
7、ed calibration data. 1.4. SI UnitsThe values stated in SI units are to be regarded as the standard. The inch-pound equivalents may be approximate. It is common practice in the engineering profession to concurrently use pounds to represent both a unit of mass (lbm) and of force (lbf). This implicitly
8、 combines two systems of units, that is, the absolute system and the gravitational system. 1.4.1. This standard has been written using the absolute system for water content (kilograms per cubic meter) in SI units. Conversion to the gravitational system of unit weight in lbf/ft3may be made. The recor
9、ding of water content in pound-force per cubic foot should not be regarded as nonconformance with this standard, although the use is scientifically incorrect. 1.4.2. In the U.S. Customary units system, the pound (lbf) represents a unit of force (weight). However, the use of balances or scales record
10、ing pounds of mass (lbm) or recording of density (lbm/ft3) should not be regarded as nonconformance with this standard. 1.5. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro
11、priate safety and health practices and determine the applicability of regulatory limitations prior to use. See Section 6, Hazards. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS 1b T 310-2 AASHTO 2.
12、REFERENCED DOCUMENTS 2.1. AASHTO Standards: T 99, Moisture-Density Relations of Soils Using a 2.5-kg (5.5-lb) Rammer and a 305-mm (12-in.) Drop T 180, Moisture-Density Relations of Soils Using a 4.54-kg (10-lb) Rammer and a 457-mm (18-in.) Drop T 191, Density of Soil In-Place by the Sand-Cone Method
13、 T 217, Determination of Moisture in Soils by Means of a Calcium Carbide Gas Pressure Moisture Tester T 255, Total Evaporable Moisture Content of Aggregate by Drying T 265, Laboratory Determination of Moisture Content of Soils T 272, Family of CurvesOne-Point Method 2.2. ASTM Standards: D2487, Stand
14、ard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System) D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure) D4253, Standard Test Methods for Maximum Index Density and Unit Weight of Soils Using a Vibratory Tabl
15、e D4254, Standard Test Methods for Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density D7013/D7013M, Standard Guide for Calibration Facility Setup for Nuclear Surface Gauges 3. SIGNIFICANCE 3.1. The test method described is useful as a rapid, nondestructive technique f
16、or the in-place determination of the wet density and water content of soil and soil-aggregate. 3.2. The test method is used for quality control and acceptance testing of compacted soil and rock for construction and for research and development. The nondestructive nature allows for repetitive measure
17、ments at a single test location and statistical analysis of the results. 3.3. DensityThe fundamental assumptions inherent in the methods are that Compton scattering is the dominant interaction and that the material under test is homogeneous. 3.4. MoistureThe fundamental assumptions inherent in the t
18、est method are that the hydrogen present is in the form of water as defined by T 265 and that the material under test is homogeneous. 3.5. Test results may be affected by chemical composition, sample heterogeneity, and to a lesser degree, material density and the surface texture of the material bein
19、g tested. The technique also exhibits spatial bias in that the gauge is more sensitive to water contained in the material in close proximity to the surface and less sensitive to water at deeper levels. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved
20、. Duplication is a violation of applicable law.TS 1b T 310-3 AASHTO 4. INTERFERENCES 4.1. In-Place Density Interferences: 4.1.1. The chemical composition of the sample may affect the measurement, and adjustments may be necessary. 4.1.2. The gauge is more sensitive to the density of the material in c
21、lose proximity to the surface in the Backscatter Method. Note 1The nuclear gauge density measurements are somewhat biased to the surface layers of the soil being tested. This bias has largely been corrected out of the Direct Transmission Method, and any remaining bias is insignificant. The Backscatt
22、er Method is still more sensitive to the material within the first several inches from the surface. Density measurements with direct transmission is the preferred method. 4.1.3. Oversize rocks or large voids in the source-detector path may cause higher or lower density determination, respectively. W
23、here lack of uniformity in the soil due to layering, rock, or voids is suspected, the test site should be excavated and visually examined to determine if the test material is representative of the full material in general, and if rock correction is required. 4.1.4. The sample volume is approximately
24、 0.0028 m3(0.10 ft3) for the Backscatter Method and 0.0057 m3(0.20 ft3) for the Direct Transmission Method when the test depth is 150 mm (6 in.). The actual sample volume is indeterminate and varies with the gauge and the density of the material. In general, the higher the density, the smaller the v
25、olume. 4.1.5. Other radioactive sources must not be within 10 m (30 ft) of the gauge in operation. 4.2. In-Place Moisture Content Interferences: 4.2.1. The chemical composition of the sample may dramatically affect the measurement and adjustments may be necessary. Hydrogen in forms other than water
26、will cause measurements in excess of the true value. Some chemical elements, such as boron, chlorine, and minute quantities of cadmium, will cause measurements lower than the true value. 4.2.2. The water content determined by this test method is not necessarily the average water within the volume of
27、 the sample involved in the measurement. The measurement is heavily influenced by the water content of the material closest to the surface. The volume of soil and rock represented in the measurement is indeterminate and will vary with the water content of the material. In general, the greater the wa
28、ter content of the material, the smaller the volume involved in the measurement. At 160 kg/m3(10 lb/ft3), approximately 50 percent of the typical measurement results from the water content of the upper 50 to 75 mm (2 to 3 in.). 4.2.3. Other neutron sources must not be within 10 m (30 ft) of the gaug
29、e in operation. 5. APPARATUS 5.1. Nuclear Density/Moisture GaugeAlthough exact details of construction of the gauge may vary, the system shall consist of: 5.1.1. A sealed source of high-energy gamma radiation, such as cesium or radium. 5.2. Gamma DetectorAny type of gamma detector, such as a Geiger-
30、Mueller tube(s). 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS 1b T 310-4 AASHTO 5.3. Fast Neutron SourceA sealed mixture of a radioactive material, such as americium, radium, or californium-252, an
31、d a target material such as beryllium. 5.4. Slow Neutron DetectorAny type of slow neutron detector, such as boron trifluoride or helium-3 proportional counter. 5.5. Reference StandardA block of material used for checking gauge operation, correction of source decay, and to establish conditions for a
32、reproducible reference count rate. 5.6. Site Preparation DeviceA plate, straightedge, or other suitable leveling tool that may be used for planing the test site to the required smoothness, and in the Direct Transmission Method, guiding the drive pin to prepare a perpendicular hole. 5.7. Drive PinA p
33、in not to exceed the diameter of the rod in the Direct Transmission gauge by more than 6 mm (1/4in.), or as recommended by the gauge manufacturer, used to prepare a hole in the material under test for inserting the rod. 5.7.1. A slide hammer, with a drive pin attached, may also be used both to prepa
34、re a hole in the material to be tested and to extract the pin without distortion to the hole. 5.8. Drive Pin ExtractorA tool that may be used to remove the drive pin in a vertical direction so that the pin will not distort the hole in the extraction process. 6. HAZARDS 6.1. The gauge utilizes radioa
35、ctive materials that may be hazardous to the health of the users unless proper precautions are taken. Users of the gauge must become familiar with applicable safety procedures and government regulations. 6.2. Effective user instructions together with routine safety procedures, such as source leak te
36、sts, recording and evaluation of film badge data, etc., are a recommended part of the operation and storage of this gauge. 7. CALIBRATION 7.1. Calibration of the gauge will be in accordance with Annexes A1 and A2. (See also ASTM D7013/D7013M.) 8. STANDARDIZATION 8.1. All nuclear density/moisture gau
37、ges are subject to long-term aging of the radioactive sources, detectors, and electronic systems, which may change the relationship between count rates and the material density and water content. To offset this aging, gauges are calibrated as a ratio of the measurement count rate to a count rate mad
38、e on a reference standard or to an air-gap count (for the backscatter/air-gap ratio method). The reference count rate should be in the same or higher order of magnitude than the range of measurement count rates over the useful range of the gauge. 8.2. Standardization of the gauge on the reference st
39、andard is required at the start of each days use and a permanent record of these data shall be retained. The standardization shall be performed with the gauge at least 10 m (30 ft) away from other nuclear density/moisture gauges and clear of large masses of water or other items that may affect the r
40、eference count rates. Standard counts should be taken in the same environment as the actual measurement counts. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS 1b T 310-5 AASHTO 8.2.1. Turn on the gau
41、ge and allow for stabilization according to the manufacturers recommendations. If the gauge is to be used either continuously or intermittently during the day, it is best to leave it in the “power on” condition to prevent having to repeat the stabilization (refer to the manufacturers recommendations
42、). This will provide more stable, consistent results. 8.2.2. Using the reference standard, take at least four repetitive readings at the normal measurement period and obtain the mean. If available on the gauge, one measurement of four or more times the normal period is acceptable. This constitutes o
43、ne standardization check. Use the procedure recommended by the gauge manufacturer for determining compliance with the gauge calibration curves. Without specific recommendations for the gauge manufacturer, use the procedure in Section 8.2.3. 8.2.3. If the mean of the four repetitive readings is outsi
44、de the limits set by Equation 1, repeat the standardization check. If the second standardization check satisfies Equation 1, the gauge is considered in satisfactory operating condition. If the second standardization check does not satisfy Equation 1, the gauge should be checked and verified accordin
45、g to Annexes A1 and A2, Sections A1.8 and A2.5. If the verification shows that there is no significant change in the calibration curve, a new reference standard count, No, should be established. If the verification check shows that there is a significant difference in the calibration curve, repair a
46、nd recalibrate the gauge. ( )1.96so oN N NF= (1) where: Ns= value of current standardization count; No= average of the past four values of Ns taken for prior usage; and F = factory prescale factor (contact gauge manufacturer for the factor). 9. PROCEDURE 9.1. Select a test location where the gauge w
47、ill be at least 150 mm (6 in.) away from any vertical mass. If closer than 600 mm (24 in.) to a vertical mass, such as in a trench, follow the gauge manufacturers correction procedures. 9.2. Prepare the test site in the following manner: 9.2.1. Remove all loose and disturbed material and additional
48、material, as necessary, to expose the top of the material to be tested. Note 2The spatial bias should be considered in determining the depth at which the gauge is to be seated. 9.2.2. Prepare a horizontal area sufficient in size to accommodate the gauge by planing the area to a smooth condition so a
49、s to obtain maximum contact between the gauge and material being tested. 9.2.3. The maximum void beneath the gauge shall not exceed 3 mm (1/8in.). Use native fines or fine sand to fill the voids and smooth the surface with a rigid plate or other suitable tool. The depth of the filler should not exceed approximately 3 mm (1/8in.). Note 3The placement of the gauge on the surface of the material to be tested is critical to the successful determination of density. The optimum condition is total contact between the bottom surface of the gauge a
