JGS 0530-2020

Japanese Geotechnical Society Standard (JGS 0530-2020)
Preparation of specimens of coarse granular materials for triaxial tests
1

Scope

This standard covers the preparation and mounting of specimens of coarse granular materials for triaxial testing.
The standard diameter of a specimen shall be from 300 mm, which is prepared by using soils with a maximum
particle size exceeding about 20 mm.

2

Normative references

The following standards shall constitute a part of this standard by virtue of being referenced in this standard.
The latest versions of these standards shall apply (including supplements).
JIS A 1202
JIS A 1203
JIS A 1204
JIS A 1210
JGS 0051
JGS 0520
JGS 0525
JGS 0526
JGS 0527
JGS 0541
JGS 0542

Test method for density of soil particles
Test method for water content of soils
Test method for particle size distribution of soils
Test method for soil compaction using a rammer
Method of classification of geomaterials for engineering purposes
Preparation of soil specimens for triaxial tests
Method for K0 consolidated-undrained triaxial compression (K0 ̅̅̅̅̅
CUC) test on soils with pore waterpressure measurements
Method for K0 consolidated-undrained triaxial extension (K0 ̅̅̅̅̅
CUE) test on soils with pore waterpressure measurements
Method for triaxial compression test on unsaturated soils
Method for cyclic undrained triaxial test on soils
Method for cyclic triaxial test to determine deformation properties of geomaterials

3

Equipment

3.1

Equipment for preparing specimens

The following equipment shall be used for preparing a specimen.
a)Straight knifeb)Material for leveling end faces of specimen
When using the trimming method of preparing specimens, leveling material for the end faces is primarily
gypsum. When using the negative pressure method, the material should be fine fractions separately
prepared from same sample.

c)

Mold
The mold should be separated into multiple parts and have the same height as specimen when assembled
on the pedestal. The inner diameter shall be greater than the diameter of the specimen by twice thethickness of the rubber sleeve. The mold should be of airtight structure with suction pores to ensure thatthe rubber sleeve comes into close contact with the inner surface of the mold when negative pressure isapplied.

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JGS 0530-2020d)Equipment for compacting samples
When using the compaction method to prepare specimen, the following equipment shall be prepared asneeded. Collar (for use in compacting the uppermost layer), rammer, tool for disturbing the compacted
surface, ramming rod, vibrator (top-driven or bottom-driven type), disk plate for compaction, and plastic orwooden hammer.

3.2

Other equipment

The equipment used for preparation, mounting, etc., of specimens shall conform to the following requirements.
a)

Negative pressure generator
The negative pressure generator shall be capable of applying negative pressure to bring the rubber sleeve
into close contact with the inner surface of the mold. When preparing specimens using the negative
pressure method, it is also used to support the specimen to keep its shape.

b)

Rubber sleeve
The rubber sleeve must be longer than the rubber sleeve expander. Its inner diameter should be slightly
less than the diameter of the specimen. The rubber thickness in its natural state should be about 0.5-2 mm;
however, if the particle shape or other characteristics of the sample mean there is a danger of puncturing
the rubber sleeve during testing, a thicker rubber sleeve is required.

c)

Rubber sleeve expander
The rubber sleeve expander should be cylindrical with height and inner diameter about 5-10 % greater thanthe height and diameter of the specimen. The design of the expander should ensure that the rubber sleevefits tightly to the inner surface of the expander under an applied negative pressure. Where the cap andpiston are rigidly connected, it is recommended that a two-part expander be used. In this case, there must
be an airtight joint between the two parts.

d)Filter
The permeability of the filter must be greater, by a suitable margin, than that of the specimen. The filter
must be fine enough to ensure that fine fractions do not escape.

Note 1:

When fitting filters to the cap and the pedestal in order to drain water both upward and downward, a low-compressibility material with the smallest possible coefficient of friction should be chosen.
Note 2: When a filter is fitted around the specimen in order to reduce consolidation time, it should be of such a shape thatits influence on the specimen shear deformation is minimized, such as by providing a slit in the filter.

e)Rubber cord and tool for fastening rubber sleeve
Fastening force must be sufficient to prevent leakage.

f)

Instrument for measuring specimen size
The dimensions of the specimen are measured with a caliper, a linear steel ruler, or a steel measuring tape.
The measurement by these instruments must be at least 0.1 % of the dimension being measured. The
diameter of a specimen is preferably measured with a steel measuring tape.

g)

Weighing scale
The weighing scale shall have a precision of 0.1 g or better.

h)

Sieve
As stipulated in JIS Z 8801-1 Test sieves – Part 1: Test sieves of metal wire cloth.

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JGS 0530-2020

4

Methods of preparing and installing specimens

4.1

Specimen preparation methods and their selection

Two methods of preparing specimens are available, as follows.
a)Trimming method
The trimming method shall be used for samples that are stable and in large pieces, either at room
temperature or frozen, including those that are cut on site into the required dimensions. In principle, theside surface of a specimen is not shaped in the laboratory.

b)

Negative pressure method
The negative pressure method shall be used for samples obtained in a loosened state and that cannot be
formed into large pieces by compaction and consolidation. It shall be also used for those that may deform
under its own weight when the mold is removed, even if compaction gives the sample reasonable stability.

4.2

Shape and dimensions of test specimens

The shape and dimensions of the test specimens shall be as follows:a)

The specimen shall have a cylindrical shape.

b)

The standard diameter of the specimen shall be 300 mm, and it shall be at least 10 times the maximum
particle size of the sample.

Note:

The diameter of the specimen may be about 5 times the maximum particle size of a sample for soils having a wide

range of particle sizes.

c)

The standard height of the specimen shall be 2.0 to 2.5 times the diameter.

4.3

Preparation and measurement of specimens by trimming method

Following the procedures listed in a) through e), specimens must be prepared with care so as to avoid changes
in sample water content. In principle, the sample should be of the same diameter as the specimen and it should
be a little higher. Before molding frozen samples, cool the specimen preparation equipment. During molding
and when measuring the dimensions of the specimen, the work must be performed quickly so as to avoid meltingof the sample.
a)With a straight knife, etc., shape the end faces of the specimen. If it is difficult to shape the end faces of
undisturbed samples collected from the site, use a leveling material to form a cap on the upper and lower
end faces of the specimen. This ensures that the upper and lower end faces of the specimen are flat andperpendicular to the axial direction.

b)

Measure the diameter of the specimen in two orthogonal directions with a precision of 0.1 % or better, at
upper, middle and lower positions of the specimen. Take the mean value of the three measurements as theinitial diameter Di (mm) of the specimen.

c)

Measure the height of the specimen with a precision of 0.1 % or better at three or more points that areassigned by dividing evenly the circumference of the specimen. Take the mean value as the initial heightHi (mm) of the specimen.

d)Measure the mass mi (g) of the specimen with a precision of 0.1% of the mass or better.

Note:

Use the following equations to obtain the wet density ρti (Mg/m3), dry density ρdi (g/cm3), void ratio ei, degree ofsaturation Sri (%), and relative density Dri (%) of the specimen in the initial state, as needed.

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JGS 0530-2020

ρti =

mi
ms
× 1000, ρdi =× 1000ViViei =Vi /1000 × ρs
−1
ms

Sri =

ρ
mi − ms× s × 100
Vi /1000 × ρs − ms ρw

Dri =emax − ei 100emax − emin

where
Vi:
ρs:
ρ w:
ms:
emax:
emin:

Initial volume of the specimen (mm3) (Vi = πD2i Hi /4)
Density of the soil particle (Mg/m3)
Density of water (Mg/m3)
Oven-dried mass of specimen (g)Void ratio of the sample by minimum density test
Void ratio of the sample by maximum density teste)

A representative sample of the specimen shall be taken from the soil removed when forming the specimen,
for which the water content shall be measured to obtain the initial water content of the specimen w i (%).

4.4

Preparation and measurement of specimens by negative pressure method

When using the negative pressure method, specimens shall be prepared and measured as follows. Figure 1
shows a specimen in the process of preparation by the negative pressure method.
a)Regulate the particle size of the sample by sieving, as needed.

Note:Control the water content of the sample as needed. Moreover, if a saturated sample is being tested, permeate asufficient amount of deaerated water into the sample to remove the air in advance. If the particle size distribution and dry
density of the specimen to be prepared are specified, adjust the samples by the non-drying method or the air-drying method
and then sort them by sieving according to any of the following methods to obtain a suitable sample. Determine the watercontent wn (%) for each sorted sample group.

1)

Method of sorting into several specified particle sizes
Select appropriate sieves from the whole set of test sieves and combine them for sorting. Pass the
sample through the series of sieves. For each sieve, the soil material that remains in the next finer
sieve shall be taken as the sample for that particle size classification.

2)

Method of sorting into a single particle size using one specified sieve
Soil material that has passed or that remains on a single sieve shall be used as the sample.

Note 1:

When preparing a specimen from a sorted sample by the compaction method, calculate the mass mn* of eachparticle size group of the sample required to form the specimen to a precision of 1 g, based on the specified dry density, thespecimen’s dimensions, the mass percentage fn (%) and the water content wn (%) of each particle size group, to satisfy the
specified particle size distribution. The resulting value shall be divided by the number of layers k to determine the target
required mass per layer (mn*/k). Here, the symbols marked * are calculated values and those without * are measured values
or specified values.
Note 2:

Use the weighing scale to weigh out the required mass of each particle size group for each layer (mn*/k) and for

all layers. Aggregate the weighed values for each particle size group. The aggregated value should be taken as the sample
mass mn for each particle size group in the specimen.

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JGS 0530-2020b)

Assemble the pedestal, rubber sleeve and mold by the prescribed method. Apply negative pressure to
bring the rubber sleeve into close contact with the inner surface of the mold. Place a filter on the pedestal
as needed.

c)Fill the mold with the sample material using one of the methods given below. When the prescribed heightis reached in the mold, smooth the upper surface of the specimen. The following methods may be used tofill the mold with sample material.
1)

Water-pluviation method
Use a scoop, bowl, etc., to pour a dry sample or a sample at its natural water content into the moldfilled with deaerated water in advance. The amount added each time should be adjusted by monitoring
the drop height from the pouring point to the top surface of the specimen inside the mold. To adjust
the specimen to the prescribed density, tap the mold with a hammer or agitate it with a vibrator asneeded.

2)Compaction method
Fill the mold with the sample up to the target height in five to six separate layers using the scoop, bowl,
etc. and compact it to the prescribed density by agitation with a vibrator or hammer. Place the sample
material into the mold to ensure that large particle sizes are evenly distributed in the layers. Additionally,lightly disturb the top surface of the sample material before adding the next layer. Finish the top faceof the uppermost layer.

d)Place a cap on top of the specimen, draw the rubber sleeve around the cap and use a rubber cord, etc., toseal the rubber sleeve against the cap. Insert a filter on the top surface of the specimen as needed.

e)Apply appropriate negative pressure (typically 20-30 kN/m2) to the specimen and remove the mold. The
negative pressure must remain lower than the prescribed effective stress in the lateral direction at thetermination of consolidation. When applying the negative pressure to the specimen, vertical displacementof the cap must not be constrained so as to ensure that the isotropic stress state of the specimen is
maintained.

Note 1:

Measures shall be taken to offset the loading applied by the cap and the loading piston as needed.

Note 2:

When preparing specimens by the compaction method with a rammer or by tamping, note that the amount ofparticle breakage varies greatly with the type of sample material.

f)While applying the negative pressure, measure the diameter of the specimen to the outer surface of therubber sleeve in two orthogonal directions with a precision of 0.1 % of the diameter or better, at upper,
middle and lower positions of the specimen. Taking the mean of the measured values, correct for the
thickness of the rubber sleeve as measured in advance and determine the initial diameter Di (mm) of thespecimen.

g)

Measure the height of the specimen with a precision of 0.1 % of the height or better at three or more points
that are assigned by dividing evenly the circumference of the specimen, and obtain the mean value todetermine the initial height Hi (mm) of the specimen.

h)Determine the mass mi (g) of the specimen with a precision of 0.1% of the mass or better, as the difference
between the mass of the whole sample prepared in advance and that of the residual amount after preparing
the specimen. Alternatively, the whole sample can be collected and weighed after testing with a precisionof 0.1% of the mass or better.

Note:

Follow the procedure given in 4.3 d) to obtain the wet density ρti (Mg/m3), dry density ρdi (Mg/m3), void ratio ei, degreeof saturation Sri (%), and relative density Dri (%) of the specimen in the initial state as needed. If a specimen is prepared fromsorted samples by the compaction method, the oven-dried mass ms of the specimen should be obtained using the following
equation.
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JGS 0530-2020

j

j

mn
w
n=1
1+ n
100

ms =  msn = 
n=1

where
j:
mn:
msn:
wn:
i)

Number of particle size group
Mass of sample for each particle size group (g)Oven-dried mass of sample for each particle size group (g)Water content of sample for each particle size group (%)

Split a representative quantity from the original sample and measure the water content to determine theinitial water content wi (%) of the specimen as needed.

Note:

If a specimen is prepared from sorted samples by the compaction method, the water content wi (%) of the specimen

should be obtained using the following equation.

1)

Where prepared from several particle size groupsjf w
wi =  n n
n =1 100

2)Where prepared from a single particle size group
The measured water content shall be set as wi (%).

5

Specimen installation process

5.1

Mounting of specimen

The specimen shall be mounted by one of the following two methods, depending on the method of preparation
used. The axial stress acting on the upper end face of the specimen must be 10 kN/m2 or less between
placement of the cap on the top of the specimen and the application of negative pressure or cell pressure. If thecap and piston are rigidly connected in the equipment being used, apply axial compression force through thepiston in addition to the cell pressure in order to attain the prescribed isotropic stress state. The relationshipbetween applied axial compression force and cell pressure, which varies with piston diameter and weight,
should be obtained in advance.
a)Specimen prepared by trimming method
1)

Mount the specimen on the pedestal, place a cap on it, draw the rubber sleeve over the specimen,
and use rubber cords, etc., to fasten the two ends of the rubber sleeve onto the pedestal and the cap.
The following procedures may be used to mount a specimen on the pedestal, depending on the rubber
sleeve expander to be used.

Note 1:

Place filters for drainage onto the upper and lower surfaces and around the side of the specimen as needed.

Note 2:

Use a cap and pedestal without drainage holes, or place flat, rigid water-impermeable plate of the same diameteras the specimen on the cap and pedestal, as needed.
Note 3:In the case of a frozen specimen, pre-cool the cap and pedestal as needed.

1.1)

Procedure when using a split (two-part) rubber sleeve expander

1.1.1)

6

Place the specimen on the pedestal such that the axes of the specimen and pedestal arealigned.

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JGS 0530-2020

1.1.2)

Insert the rubber sleeve into the split rubber sleeve expander. Apply negative pressure to bring
the rubber sleeve into close contact with the inner surface of the expander. While maintaining
this state, lower the expander over the specimen and on to the pedestal.

1.1.3)

After lowering the top cap into contact with the specimen, fix the piston to the top plate of thetriaxial pressure cell. If the cap and piston are not rigidly connected, place the cap on thespecimen.

1.1.4)

Release the upper and lower ends of the rubber sleeve from the expander and use rubber cords,
etc., to seal the sleeve onto the cap and pedestal.

1.1.5)

Disassemble and remove the rubber sleeve expander.

1.2)

2)

Procedure when using a cylindrical rubber sleeve expander

1.2.1)

Place the specimen on the pedestal such that the axes of the specimen and pedestal arealigned.

1.2.2)

Insert the rubber sleeve into the rubber sleeve expander and use negative pressure to bring therubber sleeve into close contact with the inner surface of the expander. While maintaining thisstate, lower the expander over the specimen.

1.2.3)

Release the upper and lower ends of the rubber sleeve. Pull the lower end of the sleeve down
to cover the pedestal. Fold back the excess at the upper end of the rubber sleeve over the
expander.

1.2.4)

After lowering the cap into contact with the specimen, fix the piston to the top plate of the triaxialpressure cell. If the cap and piston are not rigidly connected, place the cap on the specimen.

1.2.5)

Unfold the upper end of the sleeve over cap.

1.2.6)

Use rubber cords, etc., to fasten the rubber sleeve onto the pedestal and the cap.

Assemble the pressure cell and inject water into the cell. Apply an appropriate magnitude of isotropicpressure to the specimen in the drained state as needed. The isotropic pressure shall be about 30
kN/m2, which must be lower than the prescribed effective stress in the lateral direction at thetermination of consolidation. At this state, measure the axial displacement ΔHi (mm) and volume
change ΔVi (mm3) with an allowable tolerance of 0.1% of the specimen height and volume, respectively.
If the specimen is frozen, thaw it by any of the following methods. If it is not possible to directly measure
the volume change ΔVi, measure the axial displacement ΔHi (mm) of the specimen with an allowable
tolerance of 0.1% of the specimen height, and calculate the volumetric change in the specimen
ΔVi (mm3) from the following equation, which assumes that an isotopic strain is produced in thespecimen.

Vi =
2.1)

3H i
Vi
Hi

Method of thawing under negative pressure
Allow the specimen to thaw while keeping it under appropriate negative pressure. The magnitudeof this negative pressure shall be about 20 kN/m2, and shall be lower than the prescribed effective
stress in the lateral direction at the termination of consolidation. After thawing, measure the heightand diameter of the specimen, with a precision of 0.1% or better, to determine the resulting axial
displacement ΔHi (mm) and volume change ΔVi (mm3) due to thawing. Assemble the pressure celland inject water into the cell. By controlling the cell pressure, negative pressure, and axial load sothat the effective isotropic stress in the specimen does not change, replace the negative pressure
with the cell pressure.

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JGS 0530-2020

2.2)

Method of thawing under cell pressure
Assemble the pressure cell and inject water into the cell. Apply cell pressure and allow thespecimen to thaw under appropriate isotropic pressure. The magnitude of this isotropic pressure
shall be about 20 kN/m2, and shall be lower than the prescribed effective stress in the lateral
direction at the termination of consolidation. Measure the resulting axial displacement ΔHi (mm)and volume change ΔVi (mm3) with an allowable tolerance of 0.1% of the specimen height andvolume, respectively.

b)Specimen prepared by the negative pressure method
1)

Assemble the pressure cell and inject water into the cell.

2)

By controlling the cell pressure, negative pressure, and axial load so that the effective isotropic stressof the specimen does not change, replace the negative pressure with the cell pressure.

5.2

Saturation of specimen

Refer to the following for the methods available to saturate the specimen. Volume changes that occur as a resultof the saturation process shall be measured as required.
a)When there is a need to increase the degree of saturation of the specimen, an appropriate combination of
the following four methods should be used according to the soil type and the state of the specimen.
1)

Passing deaerated water through the specimen under cell pressure

2)

Applying sufficient back pressure

3)

Apply methods 1) and 2) after replacing void air inside the specimen with carbon dioxide gas under acell pressure

4)

Extraction of air from within the specimen by applying a negative pressure of about 90 kN/m2 to thespecimen. In this process, in order not to apply over-consolidation history, an appropriate magnitudeof negative cell pressure shall be simultaneously applied so that the difference between the negative
pressure in the specimen and the cell pressure must be smaller than the effective stress in the lateral
direction at the termination of consolidation, and then the methods in 1) and 2) shall be applied. Supply
deaerated water while applying the negative pressure as needed.

b)

When using back pressure, apply the back pressure ub (kN/m2) to the specimen and the isotropic pressure
concurrently without changing the effective isotropic stress inside the specimen. A back pressure of about
50-200 kN/m2 shall be used. The back pressure should be increased gradually in order to avoid large
fluctuations in effective stress inside the specimen. The following procedure is appropriate: Close thedrainage valve connected to the burette and apply an appropriate increment of isotropic stress to thespecimen. Then, apply an equivalent magnitude of back pressure and open the valve. In this way, thedifference in the isotopic stress and the back pressure acting on the specimen is always maintained at theinitially set pressure difference. Repeat this operation until the back pressure reaches the prescribed value.
The increments of the isotropic pressure and the back pressure for each step shall be set by paying
attentions to keep the effective stress to be lower than the prescribed effective stress in the lateral direction
at the termination of consolidation, even when the degree of saturation of the specimen is low, exhibiting asmall B value.

c)

Measure the axial displacement ΔHi (mm) and volume change ΔVi (mm3) of the specimen that occurredfrom the initial state until prior to consolidation (before testing) with an allowable tolerance of 0.1% of thespecimen height and volume, respectively. These include ΔHi (mm) and ΔVi (mm3) measured in 5.1 a).

Note:

If the volumetric change ΔVi cannot be directly measured, then ΔVi may be calculated from the following equation,

which assumes that an isotropic strain is produced in the specimen. If ΔVi is obtained using this equation, it shall be clearlystated in the reporting items.

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JGS 0530-2020

Vi =

6

3H i
Vi
Hi

Reporting

The following items of the specimens shall be reported.
a)Type of soil

Note:

Report the density of soil particles (Mg/m3), liquid limit (%), plastic limit (%), maximum dry density (Mg/m3), andminimum dry density (Mg/m3) as needed.

b)Specimen preparation method

Note 1:

If the specimen is prepared from sorted samples, report the sample control method (non-drying method or air-drying method), sorting method (whether several particle size groups or a single particle size group), and the particle sizegroups and their percentage contributions.
Note 2:

If the specimen is prepared by the compaction method, report the compaction procedure and the specifications of

the compaction equipment.

c)

Initial height (mm), diameter (mm), and volume (mm3) of specimen

Note:

Report the wet density (Mg/m3), dry density (Mg/m3), void ratio, degree of saturation (%) and relative density (%) of

specimens in the initial state as needed.

d)

The initial mass (g) and water content (%) of the specimen

Note:

If the specimen is prepared from sorted samples, report the particle size classifications and their water content (%),

and the specified dry density (Mg/m3).

e)

The axial displacement (mm) and volume change (mm3) of the specimen that occur from the initial state
until prior to consolidation, and the measurement methods usedf)

Details of any difference between the methods specified in this standard and the methods actually used. If
the specimen is separated from a large lump sample or if part of a tube sample is used, provide sketchesof the sections taken. If the sample is prepared by compaction, report the method used along with the test
results.

Note:

g)

If necessary, report the room temperature at the time of preparation.

Other reportable matters© JGS 2015 – All rights reserved

9JGS 0530-2020

Collar
Negative pressure
Mold
Rubber sleeve
Filter (ifneeded)Rubber cord
Perforated plate
Pedestal for triaxial test

(Unit: mm)
Pedestal for compaction

Figure 1 Example of specimen preparation by negative pressure method

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