ASTM D2435-96
(Test Method)Standard Test Method for One-Dimensional Consolidation Properties of Soils
Standard Test Method for One-Dimensional Consolidation Properties of Soils
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 while subjected to incrementally applied controlled-stress loading. Two alternative procedures are provided as follows:
1.1.1 Test Method A -This 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 load increments.
1.1.2 Test Method B-Time-deformation readings are required on all load increments. Successive load increments are applied after 100% primary consolidation is reached, or at constant time increments as described in Test Method A.
Note 1-The determination of the rate and magnitude of consolidation of soil when it is subjected to controlled-strain loading is covered by Test Method D 4186.
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 specimens 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 residual (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, the load increments for which time-deformation readings are desired.
Note 2-Time-deformation readings are required to determine the time for completion of primary consolidation and for evaluating the coefficient of consolidation, cv . Since cv varies with stress level and load increment (loading or unloading), 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 regarded 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, interchangeably, 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. 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 or scales recording pounds of mass (lbm), or the recording of density in lb/ft should not be regarded as nonconformance with this test method.
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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: D 2435 – 96
Standard Test Method for
One-Dimensional Consolidation Properties of Soils
This standard is issued under the fixed designation D 2435; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
deformation readings are taken on all load increments.
1. Scope *
1.4 The values stated in SI units are to be regarded as the
1.1 This test method covers procedures for determining the
magnitude and rate of consolidation of soil when it is restrained standard. The values stated in inch-pound units are approxi-
mate and given for guidance only. Reporting of test results in
laterally and drained axially while subjected to incrementally
applied controlled-stress loading. Two alternative procedures units other than SI shall not be regarded as nonconformance
with this test method.
are provided as follows:
1.1.1 Test Method A—This test method is performed with 1.4.1 In the engineering profession it is customary practice
to use, interchangeably, units representing both mass and force,
constant load increment duration of 24 h, or multiples thereof.
unless dynamic calculations (F = Ma) are involved. This im-
Time-deformation readings are required on a minimum of two
load increments. plicitly combines two separate systems of units, that is, the
absolute system and the gravimetric system. It is scientifically
1.1.2 Test Method B—Time-deformation readings are re-
quired on all load increments. Successive load increments are undesirable to combine two separate systems within a single
standard. This test method has been written using SI units;
applied after 100 % primary consolidation is reached, or at
constant time increments as described in Test Method A. however, inch-pound conversions are given in the gravimetric
system, where the pound (lbf) represents a unit of force
NOTE 1—The determination of the rate and magnitude of consolidation
(weight). The use of balances or scales recording pounds of
of soil when it is subjected to controlled-strain loading is covered by Test
mass (lbm), or the recording of density in lb/ft should not be
Method D 4186.
regarded as nonconformance with this test method.
1.2 This test method is most commonly performed on
1.5 This standard does not purport to address all of the
undisturbed samples of fine grained soils naturally sedimented
safety concerns, if any, associated with its use. It is the
in water, however, the basic test procedure is applicable, as
responsibility of the user of this standard to establish appro-
well, to specimens of compacted soils and undisturbed samples
priate safety and health practices and determine the applica-
of soils formed by other processes such as weathering or
bility of regulatory limitations prior to use.
chemical alteration. Evaluation techniques specified in this test
method are generally applicable to soils naturally sedimented
2. Referenced Documents
in water. Tests performed on other soils such as compacted and
2.1 ASTM Standards:
residual (weathered or chemically altered) soils may require
D 422 Method for Particle-Size Analysis of Soils
special evaluation techniques.
D 653 Terminology Relating to Soil, Rock, and Contained
1.3 It shall be the responsibility of the agency requesting
Fluids
this test to specify the magnitude and sequence of each load
D 854 Test Method for Specific Gravity of Soils
increment, including the location of a rebound cycle, if
D 1587 Practice For Thin-Walled Tube Geotechnical Sam-
required, and, for Test Method A, the load increments for
pling of Soils
which time-deformation readings are desired.
D 2216 Test Method for Laboratory Determination of Water
NOTE 2—Time-deformation readings are required to determine the time (Moisture) Content of Soil and Rock
for completion of primary consolidation and for evaluating the coefficient
D 2487 Classification of Soils for Engineering Purposes
of consolidation, c . Since c varies with stress level and load increment
v v
D 2488 Practice for Description and Identification of Soils
(loading or unloading), the load increments with timed readings must be
(Visual-Manual Procedure)
selected with specific reference to the individual project. Alternatively, the
D 3550 Practice for Ring-Lined Barrel Sampling of Soils
requesting agency may specify Test Method B wherein the time-
D 3740 Practice for Minimum Requirements for Agencies
Engaged in the Testing or Inspection, or both, of Soil and
Rock as Used in Engineering Design and Construction
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
D 4186 Test Method for One-Dimensional Consolidation
and Rock and is the direct responsibility of subcommitteeD18.05 on Structural
Properties of Soil.
Current edition approved June 10, 1996. Published August 1996. Originally
published as D 2435 – 65T. Last previous edition D 2435 – 90. Annual Book of ASTM Standards, Vol 04.08.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 2435 – 96
Properties of Soils Using Controlled-Strain Loading pressure. Several other evaluation techniques exist and may
D4220 Practice for Preserving and Transporting Soil yield different estimates of the preconsolidation pressure.
Samples Therefore, the requesting agency may specify an alternate
D 4318 Test Method for Liquid Limit, Plastic Limit, and technique to estimate the preconsolidation pressure.
Plasticity Index of Soils 5.4 Consolidation test results are dependent upon the dura-
D 4452 Methods for X-Ray Radiography of Soil Samples tion of each load increment. Traditionally, the load duration is
D 4546 Test Methods for One-Dimensional Swell or Settle- the same for each increment and equal to 24 h. For some soils,
ment Potential of Cohesive Soils the rate of consolidation is such that complete consolidation
(dissipation of excess pore pressure) will require more than 24
3. Terminology
h. The apparatus in general use does not have provisions for
formal verification of pore pressure dissipation. It is necessary
3.1 Definitions—The definitions of terms used in this test
method shall be in accordance with Terminology D 653. to use an interpretation technique which indirectly determines
that consolidation is complete. This test method specifies two
4. Summary of Test Method
techniques, however the requesting agency may specify an
alternative technique and still be in conformance with this test
4.1 In this test method a soil specimen is restrained laterally
method.
and loaded axially with total stress increments. Each stress
5.5 The apparatus in general use for this test method does
increment is maintained until excess pore water pressures are
not have provisions for verification of saturation. Most undis-
completely dissipated. During the consolidation process, mea-
turbed samples taken from below the water table will be
surements are made of change in the specimen height and these
saturated. However, the time rate of deformation is very
data are used to determine the relationship between the
sensitive to degree of saturation and caution must be exercised
effective stress and void ratio or strain, and the rate at which
regarding estimates for duration of settlements when partially
consolidation can occur by evaluating the coefficient of con-
saturated conditions prevail. The extent to which partial
solidation.
saturation influences the test results may be a part of the test
5. Significance and Use
evaluation and may include application of theoretical models
other than conventional consolidation theory. Alternatively, the
5.1 The data from the consolidation test are used to estimate
test may be performed using an apparatus equipped to saturate
the magnitude and rate of both differential and total settlement
the specimen.
of a structure or earthfill. Estimates of this type are of key
5.6 This test method uses conventional consolidation theory
importance in the design of engineered structures and the
based on Terzaghi’s consolidation equation to compute the
evaluation of their performance.
coefficient of consolidation, c . The analysis is based upon the
5.2 The test results can be greatly affected by sample
v
following assumptions:
disturbance. Careful selection and preparation of test speci-
5.6.1 The soil is saturated and has homogeneous properties;
mens is required to minimize disturbance.
5.6.2 The flow of pore water is in the vertical direction;
NOTE 3—Notwithstanding the statement on precision and bias con-
5.6.3 The compressibility of soil particles and pore water is
tained in this standard, the precision of this test method is dependent on
negligible compared to the compressibility of the soil skeleton;
the competence of the personnel performing the test and suitability of the
5.6.4 The stress-strain relationship is linear over the load
equipment and facilities used. Agencies that meet the criteria of Practice
increment;
D 3740 generally are considered capable of competent and objective
testing. Users of this test method are cautioned that compliance with
5.6.5 The ratio of soil permeability to soil compressibility is
Practice D 3740 does not assure reliable testing. Reliable testing depends
constant over the load increment; and
on many factors, and Practice D 3740 provides a means of evaluation
5.6.6 Darcy’s law for flow through porous media applies.
some of these factors.
5.3 Consolidation test results are dependent upon the mag-
6. Apparatus
nitude of the load increments. Traditionally, the load is doubled
6.1 Load Device—A suitable device for applying vertical
for each increment resulting in a load-increment ratio of 1. For
loads or total stresses) to the specimen. The device should be
undisturbed samples, this load procedure has provided data
capable of maintaining specified loads for long periods of time
from which estimates of the preconsolidation pressure also
with an accuracy of 6 0.5 % of the applied load and should
referred to as the maximum past pressure, using established
permit quick application of a given load increment without
evaluation techniques, compare directly with field measure-
significant impact.
ment. Other load schedules may be used to model particular
NOTE 4—Load application generally should be completed in a time
field conditions or meet special requirements. For example, it
corresponding to 0.01 t or less. For soils where primary consolidation
may be desirable to inundate and load the specimen in
is completed in 3 min, load application should be less than 2 s.
accordance with the wetting or loading pattern expected in the
field in order to best simulate the response. Smaller than 6.2 Consolidometer—A device to hold the specimen in a
standard load increment ratios may be desirable for soils that ring that is either fixed to the base or floating (supported by
are highly sensitive or whose response is highly dependent on friction on periphery of specimen) with porous disks on each
strain rate. The test method specified to estimate the precon- face of the specimen. The inside diameter of the ring shall be
solidation pressure provides a simple technique to verify that determined to a tolerance of 0.075 mm (0.003 in.). The
one set of time readings are taken after the preconsolidation consolidometer shall also provide a means of submerging the
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 2435 – 96
specimen, for transmitting the concentric vertical load to the down to the inside diameter of the consolidometer ring with a
porous disks, and for measuring the change in height of minimum of disturbance. A cutter having the same inside
specimen. diameter as the specimen ring shall attach to or be integral with
6.2.1 Minimum Specimen Diameter—The minimum speci- the specimen ring. The cutter shall have a sharp edge, a highly
men diameter shall be 50 mm (2.00 in.). polished surface and be coated with a low-friction material.
6.2.2 Minimum Specimen Height—The minimum initial Alternatively, a turntable or trimming lathe may be used. The
specimen height shall be 12 mm (0.5 in.), but shall be not less cutting tool must be properly aligned to form a specimen of the
than ten times the maximum particle diameter. same diameter as that of the ring.
6.5 Deformation Indicator—To measure change in speci-
NOTE 5—If large particles are found in the specimen after testing,
men height, with a readability of 0.0025 mm (0.0001 in.).
include in the report this visual observation or the results of a particle size
6.6 Miscellaneous Equipment—Including timing device
analysis in accordance with Method D 422 (except the minimum sample
size requirement shall be waived). with 1 s readability, distilled or demineralized water, spatulas,
knives, and wire saws, used in preparing the specimen.
6.2.3 Minimum Specimen Diameter-to-Height Ratio—The
6.7 Balances, in accordance with Method D 2216.
minimum specimen diameter-to-height ratio shall be 2.5.
6.8 Drying Oven, in accordance with Method D 2216.
NOTE 6—The use of greater diameter-to-height ratios is recommended.
6.9 Water Content Containers, in accordance with Method
To minimize the effects of friction between the sides of the specimen and
D 2216.
ring, a diameter-to-height ratio greater than four is preferable.
6.10 Environment—Tests shall be performed in an environ-
6.2.4 Specimen Ring Rigidity—The rigidity of the ring shall
ment where temperature fluctuations are less than 6 4°C (6
be such that, under hydrostatic stress conditions in the speci-
7°F) and there is no direct exposure to sunlight.
men, the change in diameter of the ring will not exceed 0.03 %
7. Sampling
of the diameter under the greatest load applied.
6.2.5 Specimen Ring Material—The ring shall be made of a 7.1 Practices D 1587 and D 3550 cover procedures and
material that is noncorrosive in relation to the soil tested. The
apparatus that may be used to obtain undisturbed samples
inner surface shall be highly polished or shall be coated with a generally satisfactory for testing. Specimens may also be
low-friction material. Silicone grease or molybdenum disulfide
trimmed from large undisturbed block samples fabricated and
is recommended;
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