AASHTO R 74-2016 Standard Practice for Wet Preparation of Disturbed Soil Samples for Test.pdf

1、Standard Practice for Wet Preparation of Disturbed Soil Samples for Test AASHTO Designation: R 74-161Release: Group 3 (August 2016) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1a R 74-1 AASHTO Standard Practice

2、 for Wet Preparation of Disturbed Soil Samples for Test AASHTO Designation: R 74-161Release: Group 3 (August 2016) 1. SCOPE 1.1. This method describes the wet preparation of soil samples, as received from the field, for mechanical analysis and the determination of soil constants. 1.2. Method A provi

3、des for drying the field samples at a temperature not exceeding 60C (140F), making a wet separation on the 0.425-mm (No. 40) sieve and drying to a temperature not exceeding 60C (140F). Method B provides that the field sample shall be kept at a moisture content equal to or greater than the natural mo

4、isture content. Samples of such soil should be shipped to the laboratory in sealed containers and not allowed to dry out before testing. If no procedure is specified, Method A shall govern. 1.3. The values stated in SI units are to be regarded as the standard. 2. REFERENCED DOCUMENTS 2.1. AASHTO Sta

5、ndard: R 58, Dry Preparation of Disturbed Soil and Soil-Aggregate Samples for Test 3. APPARATUS 3.1. The apparatus shall consist of that listed in Section 2 of R 58, and the following: 3.1.1. Drying ApparatusA thermostatically controlled drying oven for use at 110 5C (230 9F) and a suitable device c

6、apable of drying samples at a temperature not exceeding 60C (140F). 3.1.2. Filter Funnels or Candles (Optional)Buchner funnels 254 mm (10 in.) in diameter and filter paper or filter candles. 3.1.3. Miscellaneous EquipmentPans 300 mm (12 in.) in diameter by 75 mm (3 in.) in depth or other suitable co

7、ntainers that can accommodate a 203-mm (8-in.) diameter sieve for collecting the wash water; a suitable container that will prevent loss of moisture during storage of the moist test sample. 4. SAMPLE SIZE 4.1. Moist samples having the dry masses designated for physical tests described in R 58 shall

8、be obtained. 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-1a R 74-2 AASHTO METHOD A 5. PROCEDURE 5.1. The soil sample as received from the field shall be dried thoroughly in air, in a warming oven

9、 whose temperature is not above 60C (140F), or by means of a device that will not raise the temperature of the samples above 60C (140F). The aggregations shall then be thoroughly broken up in the mortar with a rubber-covered pestle or suitable mechanical device in such a way as to avoid reducing the

10、 natural size of individual particles. A representative test sample of the amount required to perform the desired tests shall then be selected by the method of quartering or by the use of a sampler. 5.2. The portion of the air-dried sample selected for the purpose of mechanical analysis and physical

11、 tests shall be weighed and the mass recorded as the mass of the total sample uncorrected for hygroscopic moisture. The test sample shall then be separated into two portions by means of a 0.425-mm sieve. The material passing the 0.425-mm sieve shall be set aside for later recombination with addition

12、al material as described in Sections 5.3 to 5.7. 5.3. The material retained on the 0.425-mm sieve shall be placed in a pan, covered with water, and allowed to soak for a period of 2 to 24 h until the particle aggregations have become soft and broken down. 5.4. After soaking, the material shall be wa

13、shed on a 0.425-mm sieve in the following manner: The empty 0.425-mm sieve shall be set in the bottom of a pan and the liquid from the sample poured into it. Enough additional water shall be added to bring the level of the water in the pan approximately 13 mm (1/2in.) above the mesh of the sieve. A

14、portion of the soaked material not to exceed 0.45 kg (1 lb) in mass shall be placed in the water on the 0.425-mm sieve and stirred by hand at the same time the sieve is agitated up and down. If the material retained on the 0.425-mm sieve contains lumps that have not slaked or disintegrated, but whic

15、h can be crumbled or mashed between the thumb and finger so as to pass the 0.425-mm sieve, such lumps shall be broken and washed through the sieve into the pan. After all lumps have been broken up, the sieve shall be held above the soil and water in the pan and the material remaining on the sieve sh

16、all be washed with a small amount of clean water. The washed material retained on the 0.425-mm sieve shall be transferred to a clean pan. 5.5. Another increment of the soaked material, not exceeding 0.45 kg (1 lb) in mass shall be placed on the 0.425-mm sieve and washed as described in Section 5.4.

17、This procedure shall be repeated until all of the soaked sample has been washed. 5.6. The material retained on the 0.425-mm sieve shall be dried and dry-sieved on the 0.425-mm sieve. The material passing the 0.425-mm sieve in this operation shall be added to the material passing the 0.425-mm sieve o

18、btained by the procedure described in Section 5.2. The material retained on the 0.425-mm sieve shall be set aside for use in the mechanical analysis of the coarse material. 5.7. After all the soaked material has been washed, the pan containing the wash water shall be set aside and not disturbed for

19、a period of several hours until all of the soil particles have settled to the bottom of the pan and the water above the soil is clear (Note 1). As much of the clear water as possible shall then be decanted or siphoned off. The soil remaining in the pan shall be dried at a temperature not exceeding 6

20、0C (140F). The dried soil shall be ground in the mortar with a rubber-covered pestle or suitable mechanical device and combined with the material passing the 0.425-mm sieve obtained by the procedures described in Sections 5.2 and 5.6. Note 1In some instances, the wash water will not become clear in

21、a reasonable length of time, in which case the entire volume must be evaporated. 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-1a R 74-3 AASHTO 5.7.1. (Alternate Section 5.7)After all of the soaked

22、 material has been washed, the wash water and material passing the 0.425-mm sieve shall be filtered on one or more Buchner funnels that have previously been fitted with filter paper. Vacuum shall be applied to the lower end of the Buchner funnels to speed up the filtering process. After filtering, t

23、he soil shall be removed from the filter, the filter paper stripped from the damp soil, and the soil dried at a temperature not exceeding 60C (140F). The dried soil shall be ground in the mortar with a rubber-covered pestle or suitable mechanical device and combined with the material passing the 0.4

24、25-mm sieve obtained by the procedures described in Sections 5.2 and 5.6. 6. TEST SAMPLE FOR MECHANICAL ANALYSIS AND SOIL CONSTANTS 6.1. The fractions passing the 0.425-mm sieve obtained as described in Sections 5.2, 5.6, and 5.7 shall be thoroughly mixed. A portion with a mass of approximately 60 g

25、 for silt and clay soils shall be selected for mechanical analysis. The remaining portion of the material passing the 0.425-mm sieve shall be used for the determination of the soil characteristics. METHOD B 7. PROCEDURE 7.1. For rapid mechanical analysis results based on dry mass of the original mat

26、erial, select and weigh a representative portion of the material for oven-dried moisture determination. Determine the moisture content at 110 5C (230 9F). 7.1.1. Select a representative portion of the moist sample estimated to contain sufficient particles passing the 0.425-mm (No. 40) sieve to make

27、the required tests for determination of soil constants. Soak this selected portion of the moist sample in water until the particle aggregations become soft (Note 2). Samples obviously containing only particles passing the 0.425-mm (No. 40) sieve may be used in the tests to determine soil constants w

28、ithout first washing on the 0.425-mm (No. 40) sieve. Note 2In some areas it is possible that the cations of salts present in the tap water may exchange with the natural cations in the soil and alter significantly the values of the soil constants should tap water be used in the soaking and washing op

29、erations. Unless it is known that such cations are not present in the tap water, distilled or demineralized water should be used. The soaking and washing operation will remove soluble salts contained in the soil. When soluble salts are present in the soil, the wash water should be saved and evaporat

30、ed, and the salts returned to the soil sample. 7.2. After soaking, wash the material on a 0.425-mm (No. 40) sieve in the following manner: Place an empty 0.425-mm (No. 40) sieve on the bottom of a clean pan and pour the water from the soaked sample (Note 3) onto the sieve. Add sufficient water to br

31、ing the level approximately 13 mm (1/2in.) above the mesh of the sieve. Transfer the soaked material to the sieve in workable increments, stirring each increment with the fingers while agitating the sieve up and down. Crumble or mash any lumps that have not slaked, using the thumb and fingers. Raise

32、 the sieve above the water in the pan and complete the washing operation using a small amount of clean water. Discard the washed material on the sieve before placing another increment of soaked material on the sieve. Note 3In cases where heavy clays are incurred it may be advantageous to use a mecha

33、nical stirrer to form a slurry that will more readily pass the 0.425-mm (No. 40) sieve. 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-1a R 74-4 AASHTO 7.3. Set aside the pan containing the washings

34、 for a period of several hours or until the water above the particles is clear. Decant, pipet, or siphon off as much of the clear water as possible (Note 1). 7.4. Alternatively, after all the soaked material has been washed, remove most of the water by filtering the wash water on one or more Buchner

35、 funnels fitted with a filter paper or by using filter candles. Remove the moist soil from the filter paper or filter candles, and combine with the sediment remaining in the pan. 7.5. Reduce the moisture content of the material passing the 0.425-mm (No. 40) sieve until the mass reaches a putty-like

36、consistency (such as 30 to 35 drops of the cup in the liquid limit test) but never below the natural moisture content. Reduction of moisture content may be accomplished by exposure to air at ordinary room temperature, by heating in an oven at a temperature not exceeding 110C (230F), by boiling, by f

37、iltering on a Buchner funnel, or by use of filter candles. During evaporation and cooling, stir the sample often enough to prevent overdrying of the fringes and soil pinnacles on the surface. Cool the heated samples to normal room temperature before testing. For soil samples containing soluble salts

38、, use a method of water reduction that will not eliminate the soluble salts from the test sample. Protect the prepared sample, in a moisture-tight container, from further drying until all required tests have been performed. 8. KEYWORDS 8.1. Sample preparation; soil sample; soil-aggregate sample; test sample. 1Formerly T 146. First published as a practice in 2016. 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.