AASHTO T 193-2013 Standard Method of Test for The California Bearing Ratio.pdf

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1、Standard Method of Test for The California Bearing Ratio AASHTO Designation: T 193-13 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1a T 193-1 AASHTO Standard Method of Test for The California Bearing Ratio AASHT

2、O Designation: T 193-13 1. SCOPE 1.1. This test method covers the determination of the California Bearing Ratio (CBR) of pavement subgrade, subbase, and base/course materials from laboratory compacted specimens. The test method is primarily intended for, but not limited to, evaluating the strength o

3、f cohesive materials having maximum particle sizes less than 19 mm (3/4in.). 1.2. When materials having maximum particle sizes greater than 19 mm (3/4in.) are to be tested, this test method provides for modifying the gradation of the material so that the material used for tests all passes the 19.0-m

4、m (3/4-in.) sieve while the total gravel 4.75-mm (No. 4) to 75-mm (3-in.) fraction remains the same. While traditionally this method of specimen preparation has been used to avoid the error inherent in testing materials containing large particles in the CBR test apparatus, the modified material may

5、have significantly different strength properties than the original material. However, a large experience base has developed using this test method for materials for which the gradation has been modified and satisfactory design methods are in use based on the results of tests using this procedure. 1.

6、3. Past practice has shown that CBR results for those materials having substantial percentages of particles retained on the 4.75-mm (No. 4) sieve are more variable than for finer materials. Consequently, more trials may be required for these materials to establish a reliable CBR. 1.4. This test meth

7、od provides for the determination of the CBR of a material at optimum water content or a range of water content from a specified compaction test and a specified dry unit mass. The dry unit mass is usually given as a percentage of maximum dry unit mass from the compaction tests of T 99 or T 180. 1.5.

8、 The agency requesting the test shall specify the water content or range of water content and the dry unit mass for which the CBR is desired. 1.6. Unless specified otherwise by the requesting agency, or unless it has been shown to have no effect on test results for the material being tested, all spe

9、cimens shall be soaked prior to penetration. 1.7. The values stated in SI units are to be regarded as the standard. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 92, Wire-Cloth Sieves for Testing Purposes M 145, Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes

10、 R 58, Dry Preparation of Disturbed Soil and Soil-Aggregate Samples for Test T 2, Sampling of Aggregates T 88, Particle Size Analysis of Soils 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 193-

11、2 AASHTO T 89, Determining the Liquid Limit of Soils T 90, Determining the Plastic Limit and Plasticity Index of Soils 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 4

12、57-mm (18-in.) Drop T 265, Laboratory Determination of Moisture Content of Soils 3. SIGNIFICANCE AND USE 3.1. This test method is used to evaluate the potential strength of subgrade, subbase, and base course material, including recycled materials, for use in road and airfield pavements. The CBR valu

13、e obtained in this test forms an integral part of several flexible pavement design methods. 3.2. For applications where the effect of compaction water content on CBR is small, such as cohesionless, coarse-grained materials, or where an allowance is made for the effect of differing compaction water c

14、ontents in the design procedure, the CBR may be determined at the optimum water content of a specified compaction effort. The dry unit mass specified is normally the minimum percent compaction allowed by using the agencys field compaction specification. 3.3. For applications where the effect of comp

15、action water content on CBR is unknown or where it is desired to account for its effect, the CBR is determined for a range of water content, usually the range of water content permitted for field compaction by using the agencys field compaction specification. 3.4. The criteria for test specimen prep

16、aration of self-cementing (and other) materials that gain strength with time must be based on a geotechnical engineering evaluation. As directed by the engineer, self-cementing materials shall be properly cured until bearing ratios representing long-term service conditions can be measured. 4. APPARA

17、TUS 4.1. MoldsThe molds shall be cylindrical in shape, made of metal, with an internal diameter of 152.40 0.66 mm (6.0 0.026 in.) and a height of 177.80 0.46 mm (7.0 0.018 in.), and provided with an extension collar approximately 50 mm (2.0 in.) in height and a perforated base plate that can be fitt

18、ed to either end of the mold. (See Figure 1.) It is desirable to have at least three molds for each soil to be tested. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.Figure 1California Bearing Ratio App

19、aratus TS-1aT193-3AASHTO 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.Table of Measurements TRIPOD FOR DETERMINING EXPANSION SURCHARGE SPACER DISC MATERIAL STEEL * STEEL * DIMENSION A B C D E F G H I

20、J K L* M* N* P METRIC, mm 6.3 12.7 63.5 120.6 9.5 1.6 152.4 190.5 76.2 95.2 19.0 54.0 149.2 150.8 61.37 TOLERANCE, mm 1.6 0.8 0.25 ENGLISH, in. 6 3 2.416 TOLERANCE, in. 0.01 MOLD WITH EXTENSION COLLAR PISTON MATERIAL STEEL* STEEL* DIMENSION A E F G* O P Q T* U* V* W X Y Z A R S* METRIC, mm 6.3 9.5 1

21、.6 152.40 177.80 61.37 88.9 158.0 238.1 165.1 212.7 23.8 33.3 50.8 6.3 69.8 49.63 TOLERANCE, mm 0.66 0.46 0.25 0.13 ENGLISH, in. 6 7 2.416 2 1.954 TOLERANCE, in. 0.026 0.018 0.01 0.005 ADJUSTABLE STEM AND PLATE MATERIAL BRONZE DIMENSION c d e* f g h k m n* p* r s t METRIC, mm 5.6 11.9 3.2 46.04 50.8

22、 69.8 75.4 19.0 28.6 9.5 6.3 107.9 149.2 TOLERANCE, mm 1.6 ENGLISH, in. 2 TOLERANCE, in. Figure 1California Bearing Ratio Apparatus (Continued) 41212124348316121743343812875161551613214183161213327683921683816151651414323273215811613143232312438118341414875161TS-1aT193-4AASHTO 2015 by the American A

23、ssociation of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 193-5 AASHTO 4.2. Spacer DiskA circular spacer disk made of metal 150.8 0.8 mm (515/16 1/32in.) in diameter and 61.37 0.25 mm (2.416 0.01 in.) in height. (See Figure 1.)

24、 Note 1When using molds having a height of 177.80 mm (7.0 in.) (Figure 1), a spacer disk height of 61.37 mm (2.416 in.) is needed to obtain a thickness of compacted specimen that conforms to the thickness: 116.43 mm (4.584 in.) of specimens in T 99 and T 180. 4.3. RammerA rammer as specified in eith

25、er T 99 or T 180. 4.4. Apparatus for Measuring ExpansionThis consists of a swell plate with adjustable stem (Figure 1) and a tripod support for a dial indicator (Figure 1). The swell plate is made of metal, 149.2 1.6 mm (57/8 1/16in.) in diameter and is perforated with 1.6-mm (1/16-in.) diameter hol

26、es. The tripod used to support the dial indicator is arranged to fit the mold extension collar. 4.5. IndicatorsTwo dial indicators: each indicator shall have a 25-mm (1-in.) throw and read to 0.02 mm (0.001 in.). 4.6. Surcharge WeightsOne annular metal weight with a center hole approximately 54.0 mm

27、 (21/8in.) in diameter and several slotted or split metal weights, all 149.2 1.6 mm (57/8 1/16in.) in diameter and each having a mass of 2.27 0.04 kg (5 0.10 lb) (Figure 1) (Note 2). Note 2When using split weights, the mass of the pair shall be 2.27 0.04 kg (5 0.10 lb). 4.7. Penetration PistonA meta

28、l piston of circular cross-section having a diameter of 49.63 0.13 mm (1.954 0.005 in.) area = 1935 mm2(3 in.2) and not less than 102 mm (4 in.) long. (See Figure 1.) 4.8. Loading DeviceA compression-type apparatus capable of applying a uniformly increasing load up to a capacity sufficient for the m

29、aterial being tested at a rate of 1.3 mm/min. (0.05 in./min.), used to force the penetration piston into the specimen. 4.9. Soaking TankA soaking tank suitable for maintaining the water level 25 mm (1 in.) above the top of the specimens. 4.10. Drying OvenA thermostatically controlled drying oven cap

30、able of maintaining a temperature of 110 5C (230 9F) for drying moisture samples. 4.11. Moisture Content ContainersAs specified in T 265. 4.12. MiscellaneousMiscellaneous tools such as mixing pans, spoons, straightedge, filter paper, balances, etc. 5. SAMPLE 5.1. The sample shall be handled and spec

31、imen(s) for compaction shall be prepared in accordance with the procedures given in T 99 or T 180 for compaction in a 152.4-mm (6-in.) mold except as follows: 5.1.1. If all material passes a 19.0-mm (3/4-in.) sieve, the entire gradation shall be used for preparing specimens for compaction without mo

32、dification. If there is material retained on the 19.0-mm sieve, the material retained on the 19.0-mm sieve shall be removed and replaced by an equal amount of material passing the 19.0-mm sieve and retained on the 4.75-mm (No. 4) sieve obtained by separation from portions of the sample not otherwise

33、 used for testing. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 193-6 AASHTO 5.1.2. Bearing Ratio at Optimum Water ContentFrom a sample having a mass of 35 kg (75 lb) or more, select a represe

34、ntative portion having a mass of approximately 11 kg (25 lb) for a moisture-density test and divide the remainder of the sample to obtain three representative portions having a mass of approximately 6.8 kg (15 lb) each. 5.1.3. Bearing Ratio for a Range of Water ContentFrom a sample having a mass of

35、113 kg (250 lb) or more, select at least five representative portions having a mass of approximately 6.8 kg (15 lb) each for use in developing each compaction curve. 6. MOISTURE-DENSITY RELATION 6.1. Bearing Ratio at Optimum Water ContentUsing the 11-kg (25-lb) portion prepared as described in Secti

36、on 5.1, determine the optimum moisture content and maximum dry density in accordance with the compaction method specified, either T 99 or T 180. A previously performed compaction test on the same material may be substituted for the compaction test just described, provided that if the sample contains

37、 material retained on the 19.0-mm (3/4-in.) sieve, soil prepared as described in Section 5.1 is used (Note 3). Note 3Maximum dry unit mass obtained from a compaction test performed in a 101.6-mm (4-in.) diameter mold may be slightly greater than the maximum dry unit weight obtained from compaction i

38、n the 152.4-mm (6-in.) compaction mold or CBR mold. 6.2. Bearing Ratio for a Range of Water ContentUsing the 6.8-kg (15-lb) specimens prepared as described in Section 5.1, determine the optimum moisture content and maximum dry density in accordance with the compaction method specified, either T 99 (

39、Method D) or T 180 (Method D), except that the CBR molds shall be used and each specimen shall be penetrated for CBR determination. In addition, the complete moisture-density relationship for 25-blow and 10-blow per layer compactions shall be developed and each test specimen compacted shall be penet

40、rated. Perform all compaction in CBR molds. In cases where the specified unit mass is at or near 100-percent maximum dry unit mass, it will be necessary to include a compactive effort greater than 56 blows per layer (Note 4). Note 4A semilog plot of dry unit mass versus compactive effort usually giv

41、es a straight-line relation when compactive effort in J/m3(ft-lb/ft3) is plotted on the log scale. This type of plot is useful in establishing the compactive effort and number of blows per layer needed to bracket the specified dry unit mass and water content range. 6.2.1. If the soaked CBR is to be

42、determined, take a representative sample of the material, for the determination of moisture, at the beginning of compaction of each specimen and another sample of the remaining material after compaction of each specimen. Use T 265 to determine the moisture content. If the unsoaked CBR is to be deter

43、mined, take a moisture content sample in accordance with T 99 or T 180 if the average moisture content is desired. 7. PROCEDURE 7.1. Bearing Ratio at Optimum Water Content: 7.1.1. Normally, three specimens must be compacted so that their compacted densities range from 95 percent (or lower) to 100 pe

44、rcent (or higher) of the maximum dry density determined in Section 6.1. Note 5Generally about 10, 30, and 65 blows per layer are suitable for compacting specimens 1, 2, and 3, respectively. More than 56 blows per layer are generally required to mold a CBR specimen to 100 percent of the maximum dry d

45、ensity determined by T 99 (Method D); this is due to the sample for the moisture-density test being reused, while the sample for the CBR specimen is mixed and compacted only once. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a vio

46、lation of applicable law.TS-1a T 193-7 AASHTO Note 6Some laboratories may prefer to test only one specimen that would be compacted to maximum dry density at optimum moisture content as determined by either T 99 or T 180. 7.1.2. Clamp the mold to the base plate, attach the extension collar and weigh

47、to the nearest 5 g (0.01 lb). Insert the spacer disk into the mold and place a coarse filter paper on top of the disk. 7.1.3. Mix each of the three 6.8-kg (15-lb) portions prepared in Section 5.1.2 with sufficient water to obtain the optimum moisture content determined in Section 6.1. 7.1.4. Compact

48、 the first of the three portions of soil-water mixture into the mold, using three equal layers and appropriate rammer, if maximum density was determined by T 99, or five equal layers if maximum density was determined by T 180, to give a total compacted depth of about 125 mm, compacting each layer wi

49、th the lowest selected number of blows in order to give a compacted density of 95 percent or less of the maximum density. 7.1.5. Determine the moisture content of the material being compacted at the beginning and end of the compaction procedure (two samples). Each moisture sample shall have a mass of at least 100 g for fine-grained soils and 500 g for coarse-grained soils. Determination of moisture content shall be done in accordance with T 265, Laboratory Determinati