ASTM D8359-21

Standard Test Method for Determining the In Situ Rock Deformation Modulus and Other Associated Rock Properties Using a Flexible Volumetric Dilatometer

SIGNIFICANCE AND USE
5.1 The dilatometer test is usually performed in vertical boreholes. It can be used in inclined or horizontal holes, but the probe would drag along the borehole wall.  
5.2 Deformation modulus of rock, creep characteristics, rebound, and permanent set data is obtained and is useful for engineering designs.  
5.3 The rock mass discontinuities, in situ stresses, geologic history, crystallography, texture, fabric, and other factors will determine the rock mass properties that laboratory size tests alone may not be able to measure and that the dilatometer test may be better able to measure.  
5.4 Determination of rock mass deformability yields a critical parameter in the design of foundations of dams, support of underground excavations, piers, caissons, and stability of rock slopes.
Note 2: Although a rock mass behaves in an anisotropic and inhomogeneous manner, the calculations for a rock mass deformation modulus are based on assumptions of elasticity and homogeneity. However, they still render results that are practical, simple, usable, and not significantly different from those obtained using inhomogeneity and inelasticity.
Note 3: The existing in situ stresses can only be estimated by in situ tests on the rock mass, such as this or other tests.  
5.5 In situ tests such as this one provides general information regarding rock mass behavior. Dilatometer tests are advised when designing and constructing specific structures.  
5.6 Dilatometer tests can be performed at a reasonable cost and effort. Dilatometer tests are also less expensive and time-consuming compared to other deformability tests like radial jack or flexible plate tests that require underground excavation and access too.  
5.7 Dilatometer modulus can be correlated with the moduli obtained by other methods (for example, the plate loading or radial jacking methods). The correlated dilatometer modulus can then be used instead of other more expensive in situ modulus tests.  
5.8 Dilatometer tests ca...
SCOPE
1.1 This test method establishes the guidelines, requirements, procedure, and analyses for determining the in situ deformation modulus of a rock mass and other ancillary data using a flexible volumetric dilatometer in an N-size, 75.7 mm (2.98 in.) drill hole (Fig. 1 and Fig. 2). Cyclic, creep, and unloading cycles are not covered in detail in this standard but may be added in the future or with a separate test standard, practice, or guide.
FIG. 1 General Depiction of a Flexible Dilatometer, Deflated (a) and Inflated (b) in a Borehole  
FIG. 2 Cross-Sections of the Borehole and Dilatable Membrane Portion of the Dilatometer in the Uninflated, r = 0, Starting Position  
Note 1: Other rock mass deformability tests are radial jack tests, flat jack tests, flexible plate tests, and borehole jack tests.  
1.2 This test method applies mainly to a commercially available flexible, volumetric dilatometer for an N-size, (75.7-mm (2.98-in.) I.D.) borehole that is inflated and deflated hydraulically in the borehole. However, the test method could apply to other dilatometers, including pneumatically inflated, or for different borehole sizes as well as covered under the British Standards Institute EN ISO 22476-5 (https://geotechnicaldesign.info). Use of a different diameter or type of volumetric dilatometer is up to the owner or project manager and shall not be regarded as nonconformance with this standard.  
1.3 Purpose, Application, Range of Uses, and Limitations:  
1.3.1 This designation is described in the context of obtaining data for the design, construction, or maintenance of structures on or in rock. This method can be conducted in any orientation but is usually conducted in a vertical or horizontal borehole as dictated by the design consideration.  
1.3.2 The test has no depth limits other than those imposed by the limitations of the test equipment, drill hole quality, testing personnel, and equipment to drill the holes...

General Information

• Status: Published
• Publication Date: 14-Aug-2021
• ICS: 93.020 - Earthworks. Excavations. Foundation construction. Underground works
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.12 - Rock Mechanics

Relations

• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D4719-20 - Standard Test Methods for Prebored Pressuremeter Testing in Soils
• Effective Date: 01-Jan-2020
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D6032/D6032M-17 - Standard Test Method for Determining Rock Quality Designation (RQD) of Rock Core
• Effective Date: 01-Mar-2017
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D3740-12a - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-May-2012
• Refers: ASTM D3740-12 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2012
• Refers: ASTM D3740-11 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Sep-2011
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM D3740-10 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2010
• Refers: ASTM D653-09 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Jan-2009
• Refers: ASTM D653-08a - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Dec-2008
• Refers: ASTM D653-08 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Nov-2008
• Refers: ASTM D2113-08 - Standard Practice for Rock Core Drilling and Sampling of Rock for Site Investigation
• Effective Date: 01-Oct-2008
• Refers: ASTM D4645-08 - Standard Test Method for Determination of In-Situ Stress in Rock Using Hydraulic Fracturing Method (Withdrawn 2017)
• Effective Date: 01-Jul-2008

Overview

ASTM D8359-21, "Standard Test Method for Determining the In Situ Rock Deformation Modulus and Other Associated Rock Properties Using a Flexible Volumetric Dilatometer," provides a comprehensive framework for field assessment of rock mass properties using in situ testing. This standard is maintained by ASTM International and is widely referenced in geotechnical and rock engineering, especially for infrastructure projects where understanding rock deformability is critical.

The test is typically conducted in vertical boreholes using a flexible volumetric dilatometer-an instrument that hydraulically inflates within the borehole to measure the deformation response of the surrounding rock. This method is essential for evaluating the in situ deformation modulus, creep behavior, rebound, and permanent set of rock masses, which are parameters not always accurately captured by laboratory core tests. ASTM D8359-21 outlines the equipment, procedures, calibration, and interpretation necessary to ensure reliable and meaningful results in geotechnical site investigations.

Key Topics

• In Situ Deformation Modulus Determination: Measures the rock mass modulus directly in the field, capturing the true mechanical response of the undisturbed rock mass, including the influence of discontinuities, in situ stress, and anisotropy.
• Flexible Volumetric Dilatometer Usage: Provides details on borehole preparation, probe inflation, data recording, and apparatus calibration. The preferred borehole size is N-size (75.7 mm), but the standard allows for flexibility with other diameters.
• Rock Mass Behavior: The method supports the assessment of deformation properties in all orientations of boreholes, making it versatile for varying site and design requirements.
• Economic and Practical Considerations: Compared to other in situ tests such as radial jack or flexible plate tests, dilatometer testing is generally more cost-effective and requires less extensive site preparation, particularly as it avoids underground excavations.
• Limitations and Data Interpretation: The test yields average (not anisotropic) properties around the borehole but remains a practical indicator for many engineering uses.

Applications

The use of ASTM D8359-21 is vital in the design, construction, and maintenance of structures that interact with rock, where knowledge of deformation characteristics can directly affect safety and performance. Typical applications include:

• Foundation Design for Dams and Piers: Accurate deformability assessment is critical for ensuring safe and efficient support of large civil structures.
• Underground Excavation Support: Predicting rock mass response to excavation helps in designing effective supports for tunnels, shafts, and caverns.
• Slope Stability Assessment: Understanding rock modulus and deformation contributes to reliable analysis of slope stability in mining, infrastructure, and natural hazard mitigation.
• Correlation with Other Methods: Dilatometer results can be correlated with plate load and radial jack tests, providing alternative or supplementary data for comprehensive geotechnical profiling.
• Index Logging and Quality Evaluation: Especially valuable for rapid logging in poor core recovery or highly jointed rock masses where lab testing is impractical.

Related Standards

ASTM D8359-21 is best utilized in conjunction with several related ASTM and international standards that ensure complete geotechnical site evaluation:

• ASTM D2113 - Practice for Rock Core Drilling and Sampling of Rock for Site Exploration
• ASTM D653 - Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D6032/D6032M - Test Method for Determining Rock Quality Designation (RQD) of Rock Core
• ASTM D3740 - Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• EN ISO 22476-5 - European standard for mechanically and pneumatically operated dilatometer tests

For cost-effective, in situ determination of rock deformation modulus and related properties, ASTM D8359-21 is a leading reference for civil, geotechnical, and structural engineers involved in projects built on or within rock masses.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D8359 −21
Standard Test Method for
Determining the In Situ Rock Deformation Modulus and
Other Associated Rock Properties Using a Flexible
Volumetric Dilatometer
This standard is issued under the fixed designation D8359; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope* properties, for any reason, including the in situ stress field or
fracture density, are significantly anisotropic, then this device
1.1 This test method establishes the guidelines,
cannot detect that difference.
requirements, procedure, and analyses for determining the in
1.3.4 Alargeexpansionoftheprobeinatestzonecanoccur
situ deformation modulus of a rock mass and other ancillary
due to either an oversized drill hole, weathering, lithology, or
data using a flexible volumetric dilatometer in an N-size, 75.7
discontinuities.As a result, the maximum pressure and expan-
mm (2.98 in.) drill hole (Fig. 1 and Fig. 2). Cyclic, creep, and
sion of the dilatometer would be limited. For example, for one
unloading cycles are not covered in detail in this standard but
particular dilatometer to avoid damaging the membrane in a
may be added in the future or with a separate test standard,
preferred N-size, 75.7 mm (2.98 in.) I.D., borehole, the
practice, or guide.
maximum working pressure of 30,000 kPa (4,350 lbf/in. )
NOTE 1—Other rock mass deformability tests are radial jack tests, flat
might be possible. In contrast, at 82.5 mm (3.25 in.), the
jack tests, flexible plate tests, and borehole jack tests.
maximum working pressure would drop to only 20,680 kPa
1.2 This test method applies mainly to a commercially
(3000 lbf/in. ). Furthermore, regardless of if it an oversized
available flexible, volumetric dilatometer for an N-size,
drill hole or a low modulus test interval, the maximum
(75.7-mm (2.98-in.) I.D.) borehole that is inflated and deflated
diameter (inflated) of only 85.5 mm (3.37 in.) is allowed.
hydraulically in the borehole. However, the test method could
1.3.5 The radial displacements of the borehole walls during
apply to other dilatometers, including pneumatically inflated,
pressurization are calculated from the total volume change of
or for different borehole sizes as well as covered under the
the dilatometer. As such, the test results from a volumetric
British Standards Institute EN ISO 22476-5 (https:⁄⁄geotech-
dilatometerindicatesonlytheaveragedvalueofthemodulusof
nicaldesign.info). Use of a different diameter or type of
deformation.
volumetric dilatometer is up to the owner or project manager
1.3.6 The volumetric dilatometer test does not provide the
and shall not be regarded as nonconformance with this stan-
anisotropic properties of the rock mass because it measures the
dard.
average deformation and not the deformation in specific
directions. However, by conducting dilatometer tests in bore-
1.3 Purpose, Application, Range of Uses, and Limitations:
holes oriented in different directions or taking impression
1.3.1 This designation is described in the context of obtain-
packer data in any test intervals that had developed a hydraulic
ing data for the design, construction, or maintenance of
type fracture, some aspects of the in situ anisotropic conditions
structures on or in rock. This method can be conducted in any
could be obtained.
orientation but is usually conducted in a vertical or horizontal
borehole as dictated by the design consideration. 1.4 Units—The values stated in SI units are to be regarded
1.3.2 The test has no depth limits other than those imposed
as standard. The values given in parentheses are provided for
by the limitations of the test equipment, drill hole quality, information only and are not considered standard. Reporting of
testing personnel, and equipment to drill the holes and position
test results in units other than SI shall not be regarded as
the testing assembly. nonconformance with this standard.
1.3.3 Since this is a volumetric test, only the average
1.4.1 The gravitational system of inch-pound units is used
deformation is obtained around the borehole. If the rock when dealing with inch-pound units. In the system, the pound
(lbf) represents a unit of force (weight), while the units for
mass is slugs. The slug unit is not given, unless dynamic (F =
These test methods are under the jurisdiction ofASTM Committee D18 on Soil
ma) calculations are involved.
and Rock and are the direct responsibility of Subcommittee D18.12 on Rock
Mechanics.
1.5 All observed and calculated values shall conform to the
Current edition approved Aug. 15, 2021. Published August 2021. Originally
guidelines for significant digits and rounding established in
approved in 2020. Last previous edition approved in 2020 as D8359 - 20. DOI:
10.1520/D8359-21. Practice D6026.
*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
D8359−21
FIG. 1General Depiction of a Flexible Dilatometer, Deflated (a) and Inflated (b) in a Borehole
D8359−21
FIG. 2Cross-Sections of the Borehole and Dilatable Membrane Portion of the Dilatometer in the Uninflated,r=0,Starting Position
1.5.1 Theproceduresusedtospecifyhowdataarecollected/ D6026 Practice for Using Significant Digits and Data Re-
recorded or calculated in the standard are regarded as the cords in Geotechnical Data
industry standard. In addition, they are representative of the D6032/D6032M Test Method for Determining Rock Quality
significant digits that generally should be retained. The proce- Designation (RQD) of Rock Core
dures used do not consider material variation, a purpose for
obtaining the data, special purpose studies, or any consider-
3. Terminology
ations for the user’s objectives; and it is common practice to
3.1 Definitions:
increase or reduce significant digits of reported data to be
3.1.1 Fordefinitionsofcommontechnicaltermsusedinthis
commensuratewiththeseconsiderations.Itisbeyondthescope
standard, refer to Terminology D653.
of this standard to consider significant digits used in analysis
3.1.2 material certifications, n—certifiesamaterial’schemi-
methods for engineering design.
cal and, in some cases, physical properties and states a product
1.6 This standard does not purport to address all of the
made of metal is in compliance with specific standards of
safety concerns, if any, associated with its use. It is the
international standards organizations such as ANSI, ASME,
responsibility of the user of this standard to establish appro-
and alike, and bears the heat number from the cast from which
priate safety, health, and environmental practices and deter-
the material was created.
mine the applicability of regulatory limitations prior to use.
3.1.2.1 Discussion—Also, known as a Material Test Report
1.7 This international standard was developed in accor-
(MTR).
dance with internationally recognized principles on standard-
3.2 Definitions of Terms Specific to This Standard:
ization established in the Decision on Principles for the
3.2.1 borehole wall contact, n—during the expansion of the
Development of International Standards, Guides and Recom-
dilatometer the pressure and volume at which the dilatable
mendations issued by the World Trade Organization Technical
membrane contacts the borehole wall.
Barriers to Trade (TBT) Committee.
3.2.2 correction factor “a”, n—sum of the intrinsic volu-
2. Referenced Documents
metric expansion of the dilatometer system and expansion of
2.1 ASTM Standards: the thick-walled metallic calibration tube during pressuriza-
tion.
D653 Terminology Relating to Soil, Rock, and Contained
Fluids
3.2.3 dilatometric modulus (E ), n—a average modulus of
d
D2113 Practice for Rock Core Drilling and Sampling of
deformation based on the application of a uniform radial
Rock for Site Exploration
pressure on a cylindrical cavity in a medium assumed elastic,
D3740 Practice for Minimum Requirements for Agencies
isotropic and homogeneous.
Engaged in Testing and/or Inspection of Soil and Rock as
3.2.3.1 Discussion—The dilatometric modulus is a Young’s
Used in Engineering Design and Construction
modulus to the extent that the test would yield a Young’s
D4645 Test Method for Determination of In-Situ Stress in
modulus of the medium if it were elastic and uniform
Rock Using Hydraulic Fracturing Method (Withdrawn
(seamless, stress-free); since it provides a deformation modu-
2017)
lus of the rock mass including the effects of all its peculiarities
D4719 Test Methods for Prebored Pressuremeter Testing in
and defects adapted to the volumetric flexible dilatometer
Soils
(using a formula expressed in terms of volumetric deforma-
tions). It represents an average deformation modulus in a zone
of a rock mass directly affected by the loading pattern and
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
strain.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
3.2.4 pressure correction factor (P ), n—a correction for the
c
the ASTM website.
stiffness of the membrane at corresponding volume, deter-
The last approved version of this historical standard is referenced on
www.astm.org. mined from a pressure calibration at atmospheric pressure.
D8359−21
3.2.5 volume correction factor (V ), n—the intrinsic volu- 5.3 The rock mass discontinuities, in situ stresses, geologic
c
metric expansion of the probe, and the hydraulic module, history, crystallography, texture, fabric, and other factors will
which is the small difference between the injected volume and determine the rock mass properties that laboratory size tests
the actual volume increase caused by the deformation of the alone may not be able to measure and that the dilatometer test
rock tested. may be better able to measure.
5.4 Determination of rock mass deformability yields a
4. Summary of Test Method
criticalparameterinthedesignoffoundationsofdams,support
of underground excavations, piers, caissons, and stability of
4.1 Aborehole, specified by the engineer and that meets the
test equipment specification criteria, is drilled at one or more rock slopes.
locations and to the depths for which test data is needed and
NOTE 2—Although a rock mass behaves in an anisotropic and inhomo-
following Practice D2113, including the collection of any
geneousmanner,thecalculationsforarockmassdeformationmodulusare
ancillary data such as RQD (D6032/D6032M) or test samples.
based on assumptions of elasticity and homogeneity. However, they still
render results that are practical, simple, usable, and not significantly
If the borehole requires support, cementing, grouting, or
different from those obtained using inhomogeneity and inelasticity.
casing, proper methods are employed as needed; including the
NOTE 3—The existing in situ stresses can only be estimated by in situ
use of interval or staged drilling and testing, to obtain satis-
tests on the rock mass, such as this or other tests.
factory borehole intervals in the rock mass for testing and for
5.5 In situ tests such as this one provides general informa-
the type and diameter of the dilatometer available for testing.
tion regarding rock mass behavior. Dilatometer tests are
4.2 Caliperlogsoftheboreholediameterand,ifpracticable,
advised when designing and constructing specific structures.
a visual inspection using an optical or acoustic televiewer of
5.6 Dilatometer tests can be performed at a reasonable cost
the borehole are run to assure the selected test interval is
and effort. Dilatometer tests are also less expensive and
suitable for testing.
time-consuming compared to other deformability tests like
4.3 The rock cores and any other pertinent data are exam-
radial jack or flexible plate tests that require underground
ined to determine which intervals of the borehole to targeted
excavation and access too.
that are within the objectives of the testing program.
5.7 Dilatometer modulus can be correlated with the moduli
4.4 Acalibrated flexible dilatometer is connected to electri-
obtained by other methods (for example, the plate loading or
cal and hydraulic cables for the readout and hydraulic equip-
radial jacking methods). The correlated dilatometer modulus
mentatthesurfaceandinsertedintoaborehole.Themembrane
can then be used instead of other more expensive in situ
section of the dilatometer is placed at the targeted test interval
modulus tests.
in the borehole and secured from moving.Aseating pressure is
5.8 Dilatometer tests can provide a qualitative evaluation of
applied to the dilatometer and then allowed time to stabilize to
a rock mass deformability before performing a large scale
the temperature in the borehole.
deformability test such as a radial jack test.
4.5 The dilatometer is expanded, by increasing the hydrau-
5.9 Dilatometers are valuable for rapid index logging of
lic pressure in predetermined steps, and the applied pressures
boreholes in jointed rocks that yield poor core recovery and
and corresponding volume changes recorded to the nearest one
inadequate specimens for laboratory testing.
on the digital display. Depending on the geology in the test
interval, the application of the pressure may be modified or
5.10 Pressurization and depressurization of the dilatable
repeated to obtain data for unloading, creep as well as tensile
membrane in this standard are unique. This is done immedi-
strength, and in situ stress.
ately upstream of the dilatable membrane by a dual-action
piston actuated from a manual pump at the surface. This
4.6 From the recorded volume and pressure values, calcu-
configuration allows the use of the dilatometer at substantial
late the in situ modulus of deformation of the rock mass. Any
depths and eliminates the parasitic expansion of the tubing and
variations in the loading sequence or additional data collected
pumping system and forces the membrane to collapse com-
for a test interval for any other rock mechanics properties
pletely regardless of if the drill hole column has fluid or not.
would be recorded and calculated as well.
5.11 The results of dilatometer tests may be used to check
4.7 After testing a section of the borehole, the dilatometer is
against the serviceability limit state of spread foundations on
completely deflated and moved to the next test interval or
rocks through a deformation analysis.
removed from the borehole if all testing was completed or if
the borehole conditions require sequential drilling and testing.
5.12 When performing a deformation analysis the Young’s
modulus, E, may be taken equal to E on the assumption that
d
5. Significance and Use
the rock is linearly elastic and isotropic.
NOTE 4—The quality of the result produced by this standard is
5.1 The dilatometer test is usually performed in vertical
dependent on the competence of the personnel performing it and the
boreholes.Itcanbeusedininclinedorhorizontalholes,butthe
suitability of the equipment and facilities used. Agencies that meet the
probe would drag along the borehole wall.
criteria of Practice D3740 are generally considered capable of competent
and objective testing/sampling/inspection/etc. Users of this standard are
5.2 Deformation modulus of rock, creep characteristics,
cautioned that compliance with Practice D3740 does not in itself assure
rebound, and permanent set data is obtained and is useful for
reliable results. Reliable results depend on many factors; Practice D3740
engineering designs. provides a means of evaluating some of those factors.
D8359−21
6. Interferences supported, the necessary equipment needed so the boreholes
may be cemented or grouted and re-drilled or cased to prepare
6.1 The inside diameter of the borehole and rock properties
the test sections in the rock mass for dilatometer tests.
of the borehole controls both range and maximum pressure
applied to the borehole wall for a given dilatometer design. 7.2 Borehole Logging Equipment:
High-quality drilling and borehole caliper measurements are 7.2.1 Borehole Caliper—Borehole device lowered into a
advised to avoid damage to the membrane and permit the borehole with a hoist that continuously measures the borehole
highest practicable test pressures, especially in high strength, diameterasithoisteduptheborehole,andaccurateto0.25-mm
stiff materials. (0.01-in.). These devices come in single and multiple arm
configurations. A six-arm configuration device is preferred.
6.2 The in situ stress field around the borehole may need to
7.2.2 Borehole Imaging—Some type of borehole TV
beincludedinthereportandwhencollectingandanalyzingthe
camera, optical or acoustic televiewer for the observation of
data. As the dilatometer membrane expands against the bore-
the borehole wall and to compare and verify geologic features
hole wall, it will simulate in some ways a hydraulic fracturing
observed in the core when the core recovery is poor or when
test. The expansion of the membrane in the borehole will be
retrieving oriented cores is advised but is not feasible.
resisted by the water head in the borehole, in situ stresses
around the borehole wall, rock mechanic properties, which 7.3 Dilatometer System—The dilatometer is a cylindrical
include the tensile strength and discontinuities.
probe basically composed of an expandable dilatometer probe,
a dual-action hydraulic module operated with a hydraulic
6.3 Calibrations of the dilatometer in one material type or
pump, and a measuring module (see Fig. 3 and Fig. 4).
diameter of a calibration tube are not sufficient for stiffer rock
types and can result in significantly lower deformation values.
NOTE 5—The following explains one type of dilatometer system but, in
If a more accurate calibration is advised, then a borehole in a general, pertains to most other systems currently being used. Therefore,
the following component specifications are not absolute and may vary
quarry site with known rock parameters may need to be
from dilatometer to dilatometer.
utilized.
7.3.1 Expandable Dilatometer Probe—The dilatometer
6.4 The dilatometer can be used in hard rock, but special
probe shown in Fig. 3 is mounted on a steel core (C) and
precautions are necessary. First, the standard loading sequence
saturated via a plugged port at its downstream extremity.
provided by the supplier is recommended. The test interval in
Saturation of the system fills the annular space between the
the borehole needs to be very tight. De-aired water should be
dilatable membrane and the steel core as well as cylinder (E)
used for reducing the deformation of the probe. Additional
with fluid. The manual hydraulic pump (see 7.5) operates the
information can be found in references (1, 2) .
dual-action hydraulic module (7.3.2) to inflate or deflate the
6.5 Themodulusofdeformationdeterminedbythedilatom-
dilatometer probe.
eter is perpendicular to the borehole axis. Whereas, most
NOTE 6—In order to use or temporarily store the dilatometer at
typical mechanical properties tests on any drill cores will be
temperatures below 0°C, water in the probe should be replaced by an
parallel to the core axis or 90 degrees from the direction of the
antifreeze solution.An ethylene-glycol-based antifreeze (regularly used in
dilatometer tests. Only the indirect tensile strength test results
engine antifreeze liquid) is recommended as it is less corrosive for the
equipment. A 50-50 solution of water-ethylene glycol by volume will
on any drill cores would be in the same direction, provided the
allow using the equipment down to –25°C.
dilatometer creates a borehole wall fracture similar to a
hydraulic fracture. 7.3.2 Dual Action Hydraulic Module—Themodule(seeFig.
3)containstwocylindersinwhichtheendsofthepistontravel.
6.6 Time for Setting the Probe in Place—Onepurposeofthe
The dual piston identified by letters (F), (G), and (H) is the
volume calibration is to knead the flexible membrane to ensure
moving part responsible for inflation or deflation of the probe.
its repeatable behavior. The effect of this kneading starts to
When the piston is fully, retracted, as shown in Fig. 3, cylinder
decay after about two hours. After this delay, this kneading
(E), is filled with fluid. When the oil is pumped immediately
should be repeated, or air will start to get into the rubber
behind the inflation piston (F), the whole piston moves
cavities, and the probe performance will be affected.
downstream, pushing water into the dilatable membrane (C).
Consequently, if it takes more than two hours to put the probe
When the manual pump is in the deflation mode, oil is pumped
at testing elevation, it is suggested to knead the membrane by
onthedownholesideofdeflationpiston(H),waterissuctioned
pressurizing it a couple of times against a casing or borehole
from the dilatable membrane (C) back into cylinder (E).
walls.
Cylinder (E) has precise dimensions so that the known volume
of fluid injected or returned from the dilatable member relative
7. Apparatus
to the position of inflation piston (F) can be determined.
7.1 Borehole Drilling Apparatus—This equipment includes
NOTE 7—This dual-action and that the expandable membrane pressur-
an assortment of excavation tools, such as drills, drilling rods,
ization is immediately upstream from the membrane by the movement of
drill casings, hoists, pumps, and auxiliary tools for drilling and
a piston actuated from a manual pump at the surface is an important
sampling N-sized, 75.7-mm (2.98-in.), I.D. test boreholes at
attribute of this module design. The fluid in the dilatable membrane (C) is
designated locations and depths. If the boreholes need to be
removed by negative pressure and just upstream of the membrane. As a
result, this assures the collapse of the membrane back to the original
diameter without any reliance on external water pressure in the borehole
The boldface numbers in parentheses refer to a list of references at the end of column, and any pressure in the hydraulic lines from the probe to the
this standard. borehole collar is a non-issue. As a result, this allows the use of the
D8359−21
FIG. 3Schematic Representation of One Variation of a Flexible Volumetric Hydraulically Inflatable Dilatometer—See text for description.
(Courtesy of Roctest)
dilatometer at great depths and eliminates the parasitic expansion of the
interface can run on a line voltage or rechargeable batteries
tubing and pumping system.
with a low battery indicator.
7.3.3 Measuring Module—The measuring module of the
7.3.5 Hydraulic Pump—A manually operated hydraulic
dilatometer (see Fig. 3) consists of an LVDT (linear variable
pump with a reservoir capacity of 2.294 L (140 in. ), and a
differential transformer). It is fixed to the upstream end of the 2
pressure rating of 0 to 70 MPa (0 to 10,000 lbf/in. ) with a
dual piston and follows piston displacement throughout the
two-way control valve to inflate or deflate the dilatometer
inflation and deflation of the membrane process. The LVDT
flexible membrane.
output is read by the readout unit or other data acquisition
7.3.6 Dial Pressure Gages—Two pressure gages are
system, which displays a reading corresponding to the axial
mounted on the hydraulic pump. The gage controlling the test
position of the piston inside the cylinder.
pressure is fixed on a metal block mounted on the inflation
7.3.4 Readout Unit or Data Acquisition Interface—A two-
circuit and has a pressure range of 0 to 35 MPa (0 to 5,000
channelportablereadoutunitorotherdataacquisitioninterface
2 2
lbf/in. ), readable to a minimum of 50 kPa (10 lbf/in. ) and an
thatcanindicatethevolumechangeoftheprobebyreadingthe
accuracy of 0.25 percent at full scale. A second gage is also
measuring module as well as the oil pressure delivered by the
fixed to a metal block mounted on the deflation circuit and has
pump. Readings are recorded manually or electronically by the
a pressure range of 0 to 14 MPa (0 to 2,000 lbf/in. ) and
data acquisition system. The unit should have an accuracy of
no less than 0.015 percent.The readout unit or data acquisition readable to a minimum of 200 kPa (25 lbf/in. ).
D8359−21
FIG. 4Example of One Type of Volumetric Dilatometer Shown in Fig. 3.
NOTE 8—The second gage on the deflation side of the pump is a safety
moduli (that is, steel and aluminum) and different wall thick-
feature to monitor the pressure and prevent over pressurization and
nesses are recommended. Material certificates (MC) for each
damage to the deflation piston.
calibration tube shall be obtained and retained for each
7.3.7 Pressure Transducer—An electronic pressure trans-
calibrationtube.Materialcertificatevaluesshallbeusedinany
ducer fixed on a metal block mounted on the inflation circuit
calculations.
and has a pressure range of 0 to 35 MPa (0 to 5,000 lbf/in. ),
NOTE 10—Thick-walled pipe for calibration tubes, cold-rolled steel
readable to 5 kPa (1 lbf/in. ) and an accuracy of 0.25 percent
tubes have dimensions and tolerances that are more accurate than
full scale.
hot-rolled steel tubes.
7.3.8 Hydraulic Hoses—High-pressure hydraulic lines con-
7.9 Recommended Ancillary Apparatus—Borehole caliper
nectthehydraulicpumptothedilatometerandthereadoutunit.
and some type of borehole TV camera, optical or acoustic
The inflation line has a working pressure of 70 MPa (10,000
televiewer is recommended to determine the internal diameter
lbf/in. ), and the deflation line has a maximum working
and condition of borehole. See 9.3.3.3.
pressure of 32 MPa (4,700 lbf/in. ). The outside diameters of
7.10 Miscellaneous Items—Measuring tape for determining
the hoses are 8 mm ( ⁄16 in.).
length of dilatometer components, funnel for filling the
NOTE 9—Two optional short hydraulic lines can be used for speeding
membrane, clipboard for manually recording data, bucket,
up the preparation and calibration process.
hydraulic oil for the pump, wrenches, screwdrivers, and
7.3.9 Electrical Cables—Standard electrical cables capable
hammer.
of sustaining 220-volt, 50-hertz operations are used for the
dilatometer test. 8. Reagents and Materials
7.4 Cable Reel, (optional)—Any reel with ample capacity 8.1 Inflation Fluid for Membrane—Distilled,demineralized,
that can handle the hydraulic hose and electrical cable while and de-aired water is the only permissible fluid for the
entering or exiting the dilatometer from the drill hole. The membrane except as noted in 8.2. The use of tap water is not
deeper the hole, the more likely a cable reel would be needed.
permitted.
7.5 Timing Device—An analog, or digital clock, stopwatch, 8.2 Ethylene-Glycol-Based Antifreeze—A 50-50 solution of
timer, or comparable device-readable to 1 second or better.
water - ethylene glycol by volume would allow using the
equipment down to –25°C, a 70-30 solution can be used down
7.6 Thermometric Device—Digital or manually readable to
to –10°C.
0.5°C or better and having an accuracy of at least 60.5°C and
capable of measuring the temperature range within which the
NOTE 11—Ethylene glycol is not environment-friendly and should be
test will be performed or the device calibrations. used and disposed of accordingly and is less corrosive for the equipment
than other antifreeze reagents.
7.7 Digital or Mechanical Caliper Gage or Pi Tape, to
measure the diameter of the dilatometer membrane readable to 9. Sampling and Test Specimens
0.25-mm (0.01-in.).
9.1 While this test method involves samples and tests
7.8 Calibration Tubes—Thick-walled pipes, with a length specimens that are in situ, it does not collect an actual sample
appropriately greater than the expanding length of the or specimen, it still requires the use of drill core samples for
instrument, with a 76.2-mm (3-in.) ID and wall thickness and planning tests or creates a drill hole that reaches the sample or
alloyofanytypeadequatetowithstandthecalibrationpressure test specimen interval. Therefore, any requirements for
range.Severalcalibrationtubesofsignificantlydifferentelastic samplesorspecimensforthedilatometertestingmayalsohave
D8359−21
toconsidertherequirementsforthecollectionandpreservation televiewer is recommended to avoid damage to the flexible
ofsamplesorspecimensforlaboratorytestingforotherreasons membrane that might be caused by open fissures or voids.
aswell,suchasfortestdataforcollaborationofthedilatometer 9.3.3.4 If a drill hole requires support, casing and/or ce-
testing. menting or sequential drilling and testing, like mismatched
drill hole and dilatometer diameters, different borehole
9.2 The dilatometer testing should be conducted or coordi-
scenarios, may be necessary. See Fig. 5.
nated with other team members so that any sampling or test
9.3.3.5 Rock cores are to be available on-site for review by
specimens are collected and handled according to any project
the dilatometer testing staff if they were not present during
requirements and standards.
drilling.
9.3 Test Site:
9.3.4 Core Logging—Drill cores are to be fully logged to
9.3.1 Test Site Selection—Prior to selecting a test site
determine the core recovery and the characteristics of the rock
location, all available surface and subsurface geological data
and jointing. Cores should be logged with special emphasis
are compiled and analyzed. A three-d
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D8359 − 20 D8359 − 21
Standard Test Method for
Determining the In Situ Rock Deformation Modulus and
Other Associated Rock Properties Using a Flexible
Volumetric Dilatometer
This standard is issued under the fixed designation D8359; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This test method establishes the guidelines, requirements, procedure, and analyses for determining the in situ deformation
modulus of a rock mass and other ancillary data using a flexible volumetric dilatometer in an NX N-size, 75.7 mm (2.98 in.) drill
hole (Fig. 1 and Fig. 2). Cyclic, creep, and unloading cycles are not covered in detail in this standard but may be added in the future
or with a separate test standard, practice, or guide.
NOTE 1—Other rock mass deformability tests are radial jack tests, flat jack tests, flexible plate tests, and borehole jack tests.
1.2 This test method applies mainly to a commercially available flexible, volumetric dilatometer for an NX-sizedN-size, (75.7-mm
(2.98-in.)) (2.98-in.) I.D.) borehole that is inflated and deflated hydraulically in the borehole. However, the test method could apply
to other dilatometers, including pneumatically inflated, or for different borehole sizes as well as covered under the British
Standards Institute EN ISO 22476-5.ISO 22476-5 (https: ⁄ ⁄geotechnicaldesign.info). Use of a different diameter or type of
volumetric dilatometer is up to the owner or project manager and shall not be regarded as nonconformance with this standard.
1.3 Purpose, Application, Range of Uses, and Limitations:
1.3.1 This designation is described in the context of obtaining data for the design, construction, or maintenance of structures on
or in rock. This method can be conducted in any orientation but is usually conducted in a vertical or horizontal borehole as dictated
by the design consideration.
1.3.2 The test has no depth limits other than those imposed by the limitations of the test equipment, drill hole quality, testing
personnel, and equipment to drill the holes and position the testing assembly.
1.3.3 Since this is a volumetric test, only the average deformation is obtained around the borehole. If the rock properties, for any
reason, including the in situ stress field or fracture density, are significantly anisotropic, then this device cannot detect that
difference.
1.3.4 A large expansion of the probe in a test zone can occur due to either an oversized drill hole, weathering, lithology, or
discontinuities. As a result, the maximum pressure and expansion of the dilatometer would be limited. For example, for one
particular dilatometer to avoid damaging the membrane in a preferred N size, N-size, 75.7 mm (2.98 in.) boreholes, I.D., borehole,
the maximum working pressure of 30,000 kPa (4,350 lbf/in. ) might be possible. In contrast, at 82.5 mm, mm (3.25 in.), the
These test methods are under the jurisdiction of ASTM Committee D18 on Soil and Rock and are the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
Current edition approved Nov. 1, 2020Aug. 15, 2021. Published December 2020August 2021. Originally approved in 2020. Last previous edition approved in 2020 as
D8359 - 20. DOI: 10.1520/D8359-20.10.1520/D8359-21.
*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
D8359 − 21
FIG. 1 General Depiction of a Flexible Dilatometer Dilatometer, Deflated (a) and Inflated (b) in a Borehole
D8359 − 21
FIG. 52 Cross-Sections B-B’ of the Borehole and Dilatable Membrane Portion of the Dilatometer in the Uninflated, r = 0, Starting Posi-
tion
maximum working pressure would drop to only 20,680 kPa. kPa (3000 lbf/in. ). Furthermore, regardless of if it an oversized drill
hole or a low modulus test interval, the maximum diameter (inflated) of only 85.5 mm (3.37 in.) is allowed.
1.3.5 The radial displacements of the borehole walls during pressurization are calculated from the total volume change of the
dilatometer. As such, the test results from a volumetric dilatometer indicates only the averaged value of the modulus of
deformation.
1.3.6 The volumetric dilatometer test does not provide the anisotropic properties of the rock mass because it measures the average
deformation and not the deformation in specific directions. However, by conducting dilatometer tests in boreholes oriented in
different directions or taking impression packer data in any test intervals that had developed a hydraulic type fracture, some aspects
of the in situ anisotropic conditions could be obtained.
1.4 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for
information only and are not considered standard. Reporting of test results in units other than SI shall not be regarded as
nonconformance with this standard.
1.4.1 The gravitational system of inch-pound units is used when dealing with inch-pound units. In the system, the pound (lbf)
represents a unit of force (weight), while the units for mass is slugs. The slug unit is not given, unless dynamic (F = ma)
calculations are involved.
1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.5.1 The procedures used to specify how data are collected/recorded or calculated in the standard are regarded as the industry
standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not
consider material variation, a purpose for obtaining the data, special purpose studies, or any considerations for the user’s
objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these
considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.
1.6 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D2113 Practice for Rock Core Drilling and Sampling of Rock for Site Exploration
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
D8359 − 21
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4645 Test Method for Determination of In-Situ Stress in Rock Using Hydraulic Fracturing Method (Withdrawn 2017)
D4719 Test Methods for Prebored Pressuremeter Testing in Soils
D6026 Practice for Using Significant Digits and Data Records in Geotechnical Data
D6032/D6032M Test Method for Determining Rock Quality Designation (RQD) of Rock Core
3. Terminology
3.1 Definitions:
3.1.1 For definitions of common technical terms used in this standard, refer to Terminology D653.
3.1.2 material certifications, n—certifies a material’s chemical and, in some cases, physical properties and states a product made
of metal is in compliance with specific standards of international standards organizations such as ANSI, ASME, and alike, and
bears the heat number from the cast from which the material was created.
3.1.2.1 Discussion—
Also, known as a Material Test Report (MTR).
3.2 Definitions of Terms Specific to This Standard:
3.2.1 borehole wall contact, n—during the expansion of the dilatometer the pressure and volume at which the dilatable membrane
contacts the borehole wall.
3.2.2 correction factor “a”, n—sum of the intrinsic volumetric expansion of the dilatometer system and expansion of the
thick-walled metallic calibration tube during pressurization.
3.2.3 dilatometric modulus (E ), n—a average modulus of deformation based on the application of a uniform radial pressure on
d
a cylindrical cavity in a medium assumed elastic, isotropic and homogeneous.
3.2.3.1 Discussion—
The dilatometric modulus is a Young’s modulus to the extent that the test would yield a Young’s modulus of the medium if it were
elastic and uniform (seamless, stress-free); since it provides a deformation modulus of the rock mass including the effects of all
its peculiarities and defects adapted to the volumetric flexible dilatometer (using a formula expressed in terms of volumetric
deformations). It represents an average deformation modulus in a zone of a rock mass directly affected by the loading pattern and
strain.
3.2.4 pressure correction factor (P ), n—a correction for the stiffness of the membrane at corresponding volume, determined from
c
a pressure calibration at atmospheric pressure.
3.2.5 volume correction factor (V ), n—the intrinsic volumetric expansion of the probe, and the hydraulic module, which is the
c
small difference between the injected volume and the actual volume increase caused by the deformation of the rock tested.
4. Summary of Test Method
4.1 A borehole, specified by the engineer and that meets the test equipment specification criteria, is drilled at one or more locations
and to the depths for which test data is needed and following Practice D2113, including the collection of any ancillary data such
as RQD (D6032/D6032M) or test samples. If the borehole requires support, cementing, grouting, or casing, proper methods are
employed as needed,needed; including the use of interval or staged drilling and testing, to obtain satisfactory borehole intervals
in the rock mass for testing and for the type and diameter of the dilatometer available for testing.
4.2 Caliper logs of the borehole diameter and, if possible,practicable, a visual inspection using an optical or acoustic televiewer
of the borehole are run to assure the selected test interval is suitable for testing.
4.3 The rock cores and any other pertinent data are examined to determine which intervals of the borehole to targeted that are
within the objectives of the testing program.
The last approved version of this historical standard is referenced on www.astm.org.
D8359 − 21
4.4 A calibrated flexible dilatometer is connected to electrical and hydraulic cables for the readout and hydraulic equipment at the
surface and inserted into a borehole. The membrane section of the dilatometer is placed at the targeted test interval in the borehole
and secured from moving. A seating pressure is applied to the dilatometer and then allowed time to stabilize to the temperature
in the borehole.
4.5 The dilatometer is expanded, by increasing the hydraulic pressure in predetermined steps, and the applied pressures and
corresponding volume changes recorded. recorded to the nearest one on the digital display. Depending on the geology in the test
interval, the application of the pressure may be modified or repeated to obtain data for unloading, creep as well as tensile strength,
and in situ stress if possible.stress.
4.6 From the recorded volume and pressure values, calculate the in situ modulus of deformation of the rock mass. Any variations
in the loading sequence or additional data collected for a test interval for any other rock mechanics properties would be recorded
and calculated as well.
4.7 After testing a section of the borehole, the dilatometer is completely deflated and moved to the next test interval or removed
from the borehole if all testing was completed or if the borehole conditions require sequential drilling and testing.
5. Significance and Use
5.1 The dilatometer test is usually performed in vertical boreholes. It can be used in inclined or horizontal holes, but the probe
would drag along the borehole wall.
5.2 Deformation modulus of rock, creep characteristics, rebound, and permanent set data is obtained and is useful for engineering
designs.
5.3 The rock mass discontinuities, in situ stresses, and the genesis, geologic history, crystallography, texture, fabric, and other
factors may causewill determine the rock mass to behave as an anisotropic, inhomogeneous, discontinuous medium properties that
laboratory size tests alone may not be able to measure and that the dilatometer test may be better able to measure.
5.4 Determination of rock mass deformability yields a critical parameter in the design of foundations of dams, support of
underground excavations, piers, caissons, and stability of rock slopes.
NOTE 2—Although a rock mass behaves in an anisotropic and inhomogeneous manner, the calculations for a rock mass deformation modulus are based
on assumptions of elasticity and homogeneity. However, they still render results that are practical, simple, usable, and not significantly different from those
obtained using inhomogeneity and inelasticity.
NOTE 3—The existing in situ stresses can only be estimated by in situ tests on the rock mass, such as this or other tests.
5.5 In situ tests such as this one provides general information regarding rock mass behavior. Dilatometer tests are advised when
designing and constructing specific structures.
5.6 Dilatometer tests can be performed at a reasonable cost and effort. Dilatometer tests are also less expensive and
time-consuming compared to other deformability tests like radial jack or flexible plate tests that require underground excavation
and access too.
5.7 Dilatometer modulus can be correlated with the moduli obtained by other methods (for example, the plate loading or radial
jacking methods). The correlated dilatometer modulus can then be used instead of other more expensive in situ modulus tests.
5.8 Dilatometer tests can provide a qualitative evaluation of a rock mass deformability before performing a large scale
deformability test such as a radial jack test.
5.9 Dilatometers are valuable for rapid index logging of boreholes in jointed rocks that yield poor core recovery and inadequate
specimens for laboratory testing.
D8359 − 21
5.10 Pressurization and depressurization of the dilatable membrane in this standard are unique. This is done immediately upstream
of the dilatable membrane by a dual-action piston actuated from a manual pump at the surface. This configuration allows the use
of the dilatometer at substantial depths and eliminates the parasitic expansion of the tubing and pumping system and forces the
membrane to collapse completely regardless of if the drill hole column has fluid or not.
NOTE 4—The quality of the result produced by this standard is dependent on the competence of the personnel performing it and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective
testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable
results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
5.11 The results of dilatometer tests may be used to check against the serviceability limit state of spread foundations on rocks
through a deformation analysis.
5.12 When performing a deformation analysis the Young’s modulus, E, may be taken equal to E on the assumption that the rock
d
is linearly elastic and isotropic.
NOTE 4—The quality of the result produced by this standard is dependent on the competence of the personnel performing it and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective
testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable
results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
6. Interferences
6.1 The size inside diameter of the borehole and rock properties of the borehole controls both range and maximum pressure
applied to the borehole wall for a given dilatometer design. High-quality drilling and borehole caliper measurements are advised
to avoid damage to the membrane and permit the highest possiblepracticable test pressures, especially in high strength, stiff
materials.
6.2 The in situ stress field around the borehole may need to be included in the report and when collecting and analyzing the data.
As the dilatometer membrane expands against the borehole wall, it will simulate in some ways a hydraulic fracturing test. The
expansion of the membrane in the borehole will be resisted by the water head in the borehole, in situ stresses around the borehole
wall, rock mechanic properties, which include the tensile strength and discontinuities.
6.3 Calibrations of the dilatometer in one material type or diameter of a calibration tube are not sufficient for stiffer rock types
and can result in significantly lower deformation values. If a more accurate calibration is advised, then a borehole in a quarry site
with known rock parameters may need to be utilized.
6.4 The use of the dilatometer is possible dilatometer can be used in hard rock, but special precautions are necessary. First, the
standard loading sequence provided by the supplier is recommended. The test interval in the borehole needs to be very tight.
Finally, de-aired De-aired water should be used for reducing the deformation of the probe. Additional information can be found
in references (1, 2) .
6.5 The modulus of deformation determined by the dilatometer is perpendicular to the borehole axis. Whereas, most typical
mechanical properties tests on any drill cores will be parallel to the core axis or 90 degrees from the direction of the dilatometer
tests. Only the indirect tensile strength test results on any drill cores would be in the same direction, provided the dilatometer
creates a borehole wall fracture similar to a hydraulic fracture.
6.6 Time for Setting the Probe in Place—One purpose of the volume calibration is to knead the flexible membrane to ensure its
repeatable behavior. The effect of this kneading starts to decay after about two hours. After this delay, this kneading should be
repeated, or air will start to get into the rubber cavities, and the probe performance will be affected. Consequently, if it takes more
than two hours to put the probe at testing elevation, it is suggested to knead the membrane by pressurizing it a couple of times
against a casing or borehole walls.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
D8359 − 21
7. Apparatus
7.1 Borehole Drilling Apparatus—This equipment includes an assortment of excavation tools, such as drills, drilling rods, drill
casings, hoists, pumps, and auxiliary tools for drilling and sampling NX (75.7-mm (2.98-in.)) N-sized, 75.7-mm (2.98-in.), I.D.
test boreholes at designated locations and depths. If the boreholes need to be supported, the necessary equipment needed so the
boreholes may be cemented or grouted and re-drilled or cased to properly expose the in situ rock in the test sections prepare the
test sections in the rock mass for dilatometer tests.
7.2 Borehole Logging Equipment:
7.2.1 Borehole Caliper—Borehole device lowered into a borehole with a hoist that continuously measures the borehole diameter
as it hoisted up the borehole, and accurate to 0.25-mm (0.01-ft).(0.01-in.). These devices come in single and multiple arm
configurations. A six-arm configuration device is preferred.
7.2.2 Borehole Imaging—Some type of borehole TV camera, optical or acoustic televiewer for the observation of the borehole wall
and to compare and verify geologic features observed in the core when the core recovery is poor or when retrieving oriented cores
is advised but is not feasible.
7.3 Dilatometer System—The dilatometer is a cylindrical probe basically composed of an expandable dilatometer probe, a
dual-action hydraulic module operated with a hydraulic pump, and a measuring module (see Fig. 23 and Fig. 34).
NOTE 5—The following explains one type of dilatometer system but, in general, pertains to most other systems currently being used. Therefore, the
following component specifications are not absolute and may vary from dilatometer to dilatometer.
7.3.1 Expandable Dilatometer Probe—The dilatometer probe shown in Fig. 23 is mounted on a steel core (C) and saturated via
a plugged port at its downstream extremity. Saturation of the system fills the annular space between the dilatable membrane and
the steel core as well as cylinder (E) with fluid. The manual hydraulic pump (see 7.5) operates the dual-action hydraulic module
(7.3.2) to inflate or deflate the dilatometer probe.
NOTE 6—In order to use or temporarily store the dilatometer at temperatures below 0°C, water in the probe should be replaced by an antifreeze solution.
An ethylene-glycol-based antifreeze (regularly used in engine antifreeze liquid) is recommended as it is less corrosive for the equipment. A 50-50 solution
of water-ethylene glycol by volume will allow using the equipment down to –25°C.
7.3.2 Dual Action Hydraulic Module—The module (see Fig. 23) contains two cylinders in which the ends of the piston travel. The
dual piston identified by letters (F), (G), and (H) is the moving part responsible for inflation or deflation of the probe. When the
piston is fully, retracted, as shown in Fig. 23, cylinder (E), is filled with fluid. When the oil is pumped immediately behind the
inflation piston (F), the whole piston moves downstream, pushing water into the dilatable membrane (C). When the manual pump
is in the deflation mode, oil is pumped on the downhole side of deflation piston (H), water is suctioned from the dilatable membrane
(C) back into cylinder (E). Cylinder (E) has precise dimensions so that the known volume of fluid injected or returned from the
dilatable member relative to the position of inflation piston (F) can be determined.
NOTE 7—This dual-action and that the expandable membrane pressurization is immediately upstream from the membrane by the movement of a piston
actuated from a manual pump at the surface is an important attribute of this module design. The fluid in the dilatable membrane (C) is removed by negative
pressure and just upstream of the membrane. As a result, this assures the collapse of the membrane back to the original diameter without any reliance
on external water pressure in the borehole column, and any pressure in the hydraulic lines from the probe to the borehole collar is a non-issue. As a result,
this allows the use of the dilatometer at great depths and eliminates the parasitic expansion of the tubing and pumping system.
7.3.3 Measuring Module—The measuring module of the dilatometer (see Fig. 23) consists of an LVDT (linear variable differential
transformer). It is fixed to the upstream end of the dual piston and follows piston displacement throughout the inflation and
deflation of the membrane process. The LVDT output is read by the readout unit or other data acquisition system, which displays
a reading corresponding to the axial position of the piston inside the cylinder.
7.3.4 Readout Unit or Data Acquisition Interface—A two-channel portable readout unit or other data acquisition interface that can
indicate the volume change of the probe by reading the measuring module as well as the oil pressure delivered by the pump.
Readings are recorded manually or electronically by the data acquisition system. The unit should have an accuracy of no less than
0.015 percent. The readout unit or data acquisition interface can run on rechargeable batteries or a line voltage of 110 volts, 60
hertz, and has or rechargeable batteries with a low battery indicator. The unit should have an accuracy of no less than 0.015 percent.
D8359 − 21
FIG. 23 Schematic Representation of One Variation of a Flexible Volumetric Hydraulically Inflatable Dilatometer. Dilatometer—See text
for description. (Courtesy of Roctest)
7.3.5 Hydraulic Pump—A manually operated hydraulic pump with a reservoir capacity of 2.294 L (140 in. ), and a pressure rating
of 0 to 70 MPa (0 to 10,000 lbf/in. ) with a two-way control valve to inflate or deflate the dilatometer flexible membrane.
7.3.6 Dial Pressure Gages—Two pressure gages are mounted on the hydraulic pump. The gage controlling the test pressure is fixed
on a metal block mounted on the inflation circuit and has a pressure range of 0 to 35 MPa (0 to 5,000 lbf/in. ), readable to a
minimum of 50 kPa (10 lbf/in. ) and an accuracy of 0.25 percent at full scale. A second gage is also fixed to a metal block mounted
on the deflation circuit and has a pressure range of 0 to 14 MPa (0 to 2,000 lbf/in. ) and readable to a minimum of 200 kPa (25
lbf/in. ).
NOTE 8—The second gage on the deflation side of the pump is a safety feature to monitor the pressure and prevent over pressurization and damage to
the deflation piston.
7.3.7 Pressure Transducer—An electronic pressure transducer fixed on a metal block mounted on the inflation circuit and has a
2 2
pressure range of 0 to 35 MPa (0 to 5,000 lbf/in. ), readable to 5 kPa (1 lbf/in. ) and an accuracy of 0.25 percent full scale.
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FIG. 34 Example of One Type of Volumetric Dilatometer Shown in Fig. 23.
7.3.8 Hydraulic Hoses—High-pressure hydraulic lines connect the hydraulic pump to the dilatometer and the readout unit. The
inflation line has a working pressure of 70 MPa (10,000 lbf/in. ), and the deflation line has a maximum working pressure of 32
MPa (4,700 lbf/in. ). The outside diameters of the hoses are 8 mm ( ⁄16 in.).
NOTE 9—Two optional short hydraulic lines can be used for speeding up the preparation and calibration process.
7.3.9 Electrical Cables—Standard electrical cables capable of sustaining 220-volt, 50-hertz operations are used for the dilatometer
test.
7.4 Cable Reel, (optional)—Any reel with ample capacity that can handle the hydraulic hose and electrical cable while entering
or exiting the dilatometer from the drill hole. The deeper the hole, the more likely a cable reel would be needed.
7.5 Timing Device—An analog, or digital clock, stopwatch, timer, or comparable device-readable to 1 second or better.
7.6 Thermometric Device—Digital or manually readable to 0.5°C or better and having an accuracy of at least 60.5°C and capable
of measuring the temperature range within which the test will be performed or the device calibrations.
7.7 Digital or Mechanical Caliper Gage or Pi Tape, to measure the diameter of the dilatometer membrane readable to 0.25-mm
(0.01-in.).
7.8 Calibration Tubes—Thick-walled pipes, with a length appropriately greater than the expanding length of the instrument, with
a 76.2-mm (3-in.) ID and wall thickness and alloy of any type adequate to withstand the calibration pressure range. Several
calibration tubes of significantly different elastic moduli (that is, steel and aluminum) and different wall thicknesses are
recommended. Material certificates (MC) for each calibration tube shall be obtained if available and retained for each calibration
tube. Material certificate values shall be used in any calculations.
NOTE 10—Thick-walled pipe for calibration tubes, cold-rolled steel tubes have dimensions and tolerances that are more accurate than hot-rolled steel
tubes.
7.9 Recommended Ancillary Apparatus—Borehole caliper and some type of borehole TV camera, optical or acoustic televiewer
is recommended to determine the internal diameter and condition of borehole. See 9.3.3.3.
7.10 Miscellaneous Items—Tape measure for measurement of the dilatometer dimensions,Measuring tape for determining length
of dilatometer components, funnel for filling the membrane, clipboard for manually recording data, bucket, hydraulic oil for the
pump, wrenches, screwdrivers, and hammer.
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8. Reagents and Materials
8.1 Inflation Fluid for Membrane—Distilled, demineralized, and de-aired water is the only permissible fluid for the membrane
except as noted in 8.2. The use of tap water is not permitted.
8.2 Ethylene-Glycol-Based Antifreeze—A 50-50 solution of water - ethylene glycol by volume would allow using the equipment
down to –25°C, a 70-30 solution can be used down to –10°C.
NOTE 11—Ethylene glycol is not environment-friendly and should be used and disposed of accordingly and is less corrosive for the equipment than other
antifreeze reagents.
9. Sampling and Test SepcimensSpecimens
9.1 While this test method involves samples and tests specimens that are in situ, it does not collect an actual sample or specimen,
it still requires the use of drill core samples for planning tests or creates a drill hole that reaches the sample or test specimen
interval. Therefore, any requirements for samples or specimens for the dilatometer testing may also have to consider the
requirements for the collection and preservation of samples or specimens for laboratory testing for other reasons as well, such as
for test data for collaboration of the dilatometer testing.
9.2 The dilatometer testing should be conducted or coordinated with other team members so that any sampling or test specimens
are collected and handled according to any project requirements.requirements and standards.
9.3 Test Site:
9.3.1 Test Site Selection—Prior to selecting a test site location, all available surface and subsurface geological data are compiled
and analyzed. A three-dimensional portrayal of these data is prepared, either in plotted form or by the construction of a plastic
model. A number of factors must be considered when selecting the test site:
(a) the spatial orientation and stress intensity of the loads to be transmitted to the rock mass by the proposed structure,
(b) the various types of material found in the rock mass and the relative volume and location of each,
(c) the spatial orientation of rock discontinuities, such as bedding, foliation, jointing, and alike, and their relationship to the
applied loads from the structure, and
(d) the fracture density of the rock mass.
9.3.2 Selection of Test Locations:
9.3.2.1 Drill hole locations and depths are to be selected by taking into account the anticipated rock quality variations and depths
of weathering, and the requirements of the designs or structures for which the test data are to be used.
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