AASHTO T 216-2007 Standard Method of Test for One-Dimensional Consolidation Properties of Soils《土壤单向固结性能的试验方法》.pdf

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1、 Standard Method of Test for One-Dimensional Consolidation Properties of Soils AASHTO Designation: T 216-07 (2012) ASTM Designation: D2435-04 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1a T 216-1 AASHTO Standa

2、rd Method of Test for One-Dimensional Consolidation Properties of Soils AASHTO Designation: T 216-07 (2012) ASTM Designation: D2435-04 1. SCOPE 1.1. This test method covers procedures for determining the magnitude and rate of consolidation of soil when it is restrained laterally and drained axially

3、while subjected to incrementally applied controlled-stress loading. Two alternative procedures are provided as follows: 1.1.1. Test Method AThis test method is performed with constant load increment duration of 24 h, or multiples thereof. Time-deformation readings are required on a minimum of two-lo

4、ad increments. 1.1.2. Test Method BTime-deformation readings are required on all load increments. Successive load increments are applied after 100 percent primary consolidation is reached, or at constant time increments as described in Test Method A. Note 1The determination of the rate and magnitude

5、 of consolidation of soil when it is subjected to controlled-strain loading is covered by ASTM D4186/D4186M. 1.2. This test method is most commonly performed on undisturbed samples of fine grained soils naturally sedimented in water; however, the basic test procedure is applicable as well to specime

6、ns of compacted soils and undisturbed samples of soils formed by other processes such as weathering or chemical alteration. Evaluation techniques specified in this test method are generally applicable to soils naturally sedimented in water. Tests performed on other soils, such as compacted and resid

7、ual (weathered or chemically altered) soils, may require special evaluation techniques. 1.3. It shall be the responsibility of the agency requesting this test to specify the magnitude and sequence of each load increment, including the location of a rebound cycle, if required, and, for Test Method A,

8、 the load increments for which time-deformation readings are desired. Note 2Time-deformation readings are required to determine the time for completion of primary consolidation and for evaluating the coefficient of consolidation, cv. Since cvvaries with stress level and load increment (loading or un

9、loading), the load increments with timed readings must be selected with specific reference to the individual project. Alternatively, the requesting agency may specify Test Method B wherein the time-deformation readings are taken on all load increments. 1.4. The values stated in SI units are to be re

10、garded as the standard. The values stated in inch-pound units are approximate and given for guidance only. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method. 1.4.1. In the engineering profession, it is customary practice to use, interchang

11、eably, units representing both mass and force, unless dynamic calculations (F = Ma) are involved. This implicitly combines two separate systems of units; that is, the absolute system and the gravimetric system. It is scientifically undesirable to combine two separate systems within a single standard

12、. This test method has been written using SI units; however, inch-pound conversions are given in the gravimetric system, where the pound (lbf) represents a unit of force (weight). The use of balances 2015 by the American Association of State Highway and Transportation Officials.All rights reserved.

13、Duplication is a violation of applicable law.TS-1a T 216-2 AASHTO or scales recording pounds of mass (lbm), or the recording of density in lb/ft3, should not be regarded as nonconformance with this test method. 1.5. This standard does not purport to address the safety concerns associated with its us

14、e. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: T 88, Particle Size Analysis of Soils T 89, Determining the Liquid Limi

15、t of Soils T 90, Determining the Plastic Limit and Plasticity Index of Soils T 100, Specific Gravity of Soils T 207, Thin-Walled Tube Sampling of Soils T 265, Laboratory Determination of Moisture Content of Soils 2.2. ASTM Standards: D653, Standard Terminology Relating to Soil, Rock, and Contained F

16、luids D2487, Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System) D2488, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure) D3550, Standard Practice for Thick Wall, Ring-Lined, Split Barrel, Drive Sampling of

17、 Soils D4186/D4186M, Standard Test Method for One-Dimensional Consolidation Properties of Saturated Cohesive Soils Using Controlled-Strain Loading D4220, Standard Practices for Preserving and Transporting Soil Samples D4452, Standard Practice for X-Ray Radiography of Soil Samples D4546, Standard Tes

18、t Methods for One-Dimensional Swell or Collapse of Cohesive Soils D6026, Standard Practice for Using Significant Digits in Geotechnical Data 3. TERMINOLOGY 3.1. DefinitionsThe definitions of terms used in this test method shall be in accordance with ASTM D653. 4. SUMMARY OF TEST METHOD 4.1. In this

19、test method, a soil specimen is restrained laterally and loaded axially with total stress increments. Each stress increment is maintained until excess pore water pressures are completely dissipated. During the consolidation process, measurements are made of change in the specimen height and these da

20、ta are used to determine the relationship between the effective stress and void ratio or strain, and the rate at which consolidation can occur by evaluating the coefficient of consolidation. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplicati

21、on is a violation of applicable law.TS-1a T 216-3 AASHTO 5. SIGNIFICANCE AND USE 5.1. The data from the consolidation test are used to estimate the magnitude and rate of both differential and total settlement of a structure or earthfill. Estimates of this type are of key importance in the design of

22、engineered structures and the evaluation of their performance. 5.2. The test results can be greatly affected by sample disturbance. Careful selection and preparation of test specimens is required to minimize disturbance. 5.3. Consolidation test results are dependent upon the magnitude of the load in

23、crements. Traditionally, the load is doubled for each increment resulting in a load-increment ratio of one. For undisturbed samples, this load procedure has provided data from which estimates of the preconsolidation pressure also referred to as the maximum past pressure, using established evaluation

24、 techniques, compare directly with field measurement. Other load schedules may be used to model particular field conditions or meet special requirements. For example, it may be desirable to inundate and load the specimen in accordance with the wetting or loading pattern expected in the field in orde

25、r to best simulate the response. Smaller than standard load increment ratios may be desirable for soils that are highly sensitive or whose response is highly dependent on strain rate. The test method specified to estimate the preconsolidation pressure provides a simple technique to verify that one s

26、et of time readings are taken after the preconsolidation pressure. Several other evaluation techniques exist and may yield different estimates of the preconsolidation pressure. Therefore, the requesting agency may specify an alternate technique to estimate the preconsolidation pressure. 5.4. Consoli

27、dation test results are dependent upon the duration of each load increment. Traditionally, the load duration is the same for each increment and equal to 24 h. For some soils, the rate of consolidation is such that complete consolidation (dissipation of excess pore pressure) will require more than 24

28、 h. The apparatus in general use does not have provisions for formal verification of pore pressure dissipation. It is necessary to use an interpretation technique that indirectly determines that consolidation is complete. This test method specifies two techniques; however, the requesting agency may

29、specify an alternative technique and still be in conformance with this test method. 5.5. The apparatus in general use for this test method does not have provisions for verification of saturation. Most undisturbed samples taken from below the water table will be saturated. However, the time rate of d

30、eformation is very sensitive to degree of saturation and caution must be exercised regarding estimates for duration of settlements when partially saturated conditions prevail. The extent to which partial saturation influences the test results may be a part of the test evaluation and may include appl

31、ication of theoretical models other than conventional consolidation theory. Alternatively, the test may be performed using an apparatus equipped to saturate the specimen. 5.6. This test method uses conventional consolidation theory based on Terzaghis consolidation equation to compute the coefficient

32、 of consolidation, cv. The analysis is based upon the following assumptions: 5.6.1. The soil is saturated and has homogeneous properties; 5.6.2. The flow of pore water is in the vertical direction; 5.6.3. The compressibility of soil particles and pore water is negligible compared to the compressibil

33、ity of the soil skeleton; 5.6.4. The stressstrain relationship is linear over the load increment; 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 216-4 AASHTO 5.6.5. The ratio of soil permeabilit

34、y to soil compressibility is constant over the load increment; and 5.6.6. Darcys law for flow through porous media applies. 6. APPARATUS 6.1. Load DeviceA suitable device for applying vertical loads or total stresses to the specimen. The device should be capable of maintaining specified loads for lo

35、ng periods of time with an accuracy of 0.5 percent of the applied load and should permit quick application of a given load increment without significant impact. Note 3Load application generally should be completed in a time corresponding to 0.01 t100or less. For soils where primary consolidation is

36、completed in 3 min, load application should be less than 2 s. 6.2. ConsolidometerA device to hold the specimen in a ring that is either fixed to the base or floating (supported by friction on periphery of specimen) with porous disks on each face of the specimen. The inside diameter of the ring shall

37、 be determined to a tolerance of 0.075 mm (0.003 in.). The consolidometer shall also provide a means of submerging the specimen, for transmitting the concentric vertical load to the porous disks, and for measuring the change in height of specimen. 6.2.1. Minimum Specimen DiameterThe minimum specimen

38、 diameter shall be 50 mm (2.00 in.). The diameter of the sample in the tube shall be greater than the diameter of the consolidation test ring. The diameter of the sample must be greater than the test ring to reduce sampling disturbance and prevent lateral displacement. 6.2.2. Minimum Specimen Height

39、The minimum initial specimen height shall be 12 mm (0.5 in.), but shall not be less than 10 times the maximum particle diameter. Note 4If large particles are found in the specimen after testing, include in the report this visual observation or the results of a particle-sized analysis in accordance w

40、ith T 88 (except the minimum sample-sized requirement shall be waived). 6.2.3. Minimum Specimen Diameter-to-Height RatioThe minimum specimen diameter-to-height ratio shall be 2.5. Note 5The use of greater diameter-to-height ratios is recommended. To minimize the effects of friction between the sides

41、 of the specimen and ring, a diameter-to-height ratio greater than four is preferable. 6.2.4. Specimen Ring RigidityThe rigidity of the ring shall be such that, under hydrostatic stress conditions in the specimen, the change in diameter of the ring will not exceed 0.03 percent of the diameter under

42、the greatest load applied. 6.2.5. Specimen Ring MaterialThe ring shall be made of a material that is noncorrosive in relation to the soil tested. The inner surface shall be highly polished or shall be coated with a low-friction material. Silicone grease or molybdenum disulfide is recommended; polyte

43、trafluoroethylene is recommended for non-sandy soils. 6.3. Porous DisksThe porous disks shall be of silicon carbide, aluminum oxide, or similar noncorrosive material. The grade of the disks shall be fine enough to prevent intrusion of soil into the pores. If necessary, a filter paper (Note 6) may be

44、 used to prevent intrusion of the soil into the disks; however, the permeability of the disks, and filter paper, if used, must be at least one order of magnitude higher than that of the specimen. Note 6Whatman No. 54 filter paper has been found to meet requirements for permeability and durability. 2

45、015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 216-5 AASHTO 6.3.1. DiameterThe diameter of the top disk shall be 0.2 to 0.5 mm (0.01 to 0.02 in.) less than the inside diameter of the ring. If a f

46、loating ring is used, the bottom disk shall have the same diameter as the top disk. Note 7The use of tapered disks is recommended, with the larger diameter in contact with the soil. 6.3.2. ThicknessThickness of the disks shall be sufficient to prevent breaking. The top disk shall be loaded through a

47、 corrosion-resistant plate of sufficient rigidity to prevent breakage of the disk. 6.3.3. MaintenanceThe disks shall be clean and free from cracks, chips, and other defects. New porous disks should be boiled for at least 10 min and left in the water to cool to ambient temperature before use. Immedia

48、tely after each use, clean the porous disks with a nonabrasive brush and boil to remove clay particles that may reduce their permeability. It is recommended that porous disks be stored in a jar with de-aired water between tests. 6.4. Specimen Trimming DeviceA trimming turntable or a cylindrical cutt

49、ing ring may be used for trimming the sample down to the inside diameter of the consolidometer ring with a minimum of disturbance. A cutter having the same inside diameter as the specimen ring shall attach to or be integral with the specimen ring. The cutter shall have a sharp edge, a highly polished surface, and be coated with a low-friction material. Alternatively, a turntable or trimming lathe may be used. The cutting tool must be properly aligned to form a specimen of the same diameter as that of the ring. 6.5. Deformation Ind