ASTM D4395-17

Standard Test Method for Determining In Situ Modulus of Deformation of Rock Mass Using Flexible Plate Loading Method

SIGNIFICANCE AND USE
5.1 Results of this type of test method are used to predict displacements in rock mass caused by loads from a structure or from underground construction. It is one of several tests that should be performed. The resulting in situ elastic modulus is commonly less than the elastic modulus determined in the laboratory.  
5.2 The modulus is determined using an elastic solution for a uniformly distributed load (uniform stress) over a circular area acting on a semi-infinite elastic medium.  
5.3 This test method is normally performed at ambient temperature, but equipment can be modified or substituted for operations at other temperatures.
Note 1: 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.
SCOPE
1.1 This test method covers the preparation, equipment, test procedure, and data reduction for determining in situ modulus of deformation of a rock mass using the flexible plate loading method.  
1.2 This test method is designed to be conducted in an adit or small underground chamber; however, with suitable modifications it could be conducted at the surface.  
1.3 This test method is usually conducted parallel or perpendicular to the anticipated axis of thrust, as dictated by the design load and to diametrically opposite surfaces.  
1.4 Both instantaneous deformation and primary creep can be obtained from this test method.  
1.5 Time-dependent tests not covered by this standard can be performed but are to be reported in another standard.  
1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.  
1.6.1 The method used to specify how data are collected, calculated, or recorded in this standard is not directly related to the accuracy to which the data can be applied in design or other uses, or both. How one applies the results obtained using this standard is beyond its scope.  
1.7 The values stated in inch-pound units are to be regarded as standard, except as noted below. The values given in parentheses are mathematical conversions to SI units that 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 test method.  
1.8 The references appended to this standard contain further information on this test method.  
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precaution statements, see Section 8.  
1.10 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.

General Information

• Status: Published
• Publication Date: 30-Jun-2017
• ICS: 93.020 - Earthworks. Excavations. Foundation construction. Underground works
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.12 - Rock Mechanics

Relations

• Replaces: ASTM D4395-08 - Standard Test Method for Determining In Situ Modulus of Deformation of Rock Mass Using Flexible Plate Loading Method
• Effective Date: 01-Jul-2017
• 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 D4403-20 - Standard Practice for Extensometers Used in Rock
• 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 D4394-17 - Standard Test Method for Determining In Situ Modulus of Deformation of Rock Mass Using Rigid Plate Loading Method
• Effective Date: 01-Jul-2017
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D4403-12 - Standard Practice for Extensometers Used in Rock
• Effective Date: 15-Aug-2012
• 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 D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• 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 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 D5434-09 - Standard Guide for Field Logging of Subsurface Explorations of Soil and Rock
• Effective Date: 01-May-2009
• 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

Overview

ASTM D4395-17, titled Standard Test Method for Determining In Situ Modulus of Deformation of Rock Mass Using Flexible Plate Loading Method, is a critical standard developed by ASTM for geotechnical and civil engineering projects. This test method establishes the procedure for measuring the in situ modulus of deformation of a rock mass using a flexible plate loading approach. The information derived from this test is essential for predicting displacements within rock masses subjected to loads from structures and underground construction projects.

The test is predominantly carried out in adits or small underground chambers but can also be adapted for surface applications. It provides valuable data on both instantaneous deformation and primary creep of rock masses, with results often serving as a supplement to laboratory-derived moduli. Compliance with this standard ensures more realistic assessments of structural behavior by capturing field-specific factors that cannot be duplicated in laboratory settings.

Key Topics

• In situ modulus of deformation: Measures the actual deformation properties of the rock mass under field conditions, which are commonly lower than laboratory values due to inhomogeneities and discontinuities in the rock.
• Flexible plate loading method: A test methodology that utilizes hydraulic flat jacks and load measuring devices to apply, maintain, and release test loads over defined rock surfaces.
• Test setup and procedure: Involves precise preparation of rock surfaces, installation of deformation measuring instruments, incremental loading cycles, and data collection for modulus calculations.
• Surface and sub-surface measurement: Captures deformations both at the rock surface and within the rock mass to evaluate average properties and identify localized variations.
• Data reporting and quality assurance: Emphasizes thorough documentation, adherence to practices for significant digits and rounding, and rigorous quality checks according to ASTM guidelines.

Applications

The flexible plate loading method described in ASTM D4395-17 is widely used for:

• Civil infrastructure: Assessing rock mass responses beneath dams, tunnels, underground chambers, and foundations to ensure safe and reliable design.
• Mining and underground construction: Predicting roof or wall displacement in mines and excavations, assisting with support system design.
• Rock engineering investigations: Supplementing laboratory testing data with field-derived properties for a holistic understanding of site-specific rock behavior.
• Design of load-bearing structures: Providing data for accurate analysis of settlements and stress-strain relationships, especially where large or complex loads are anticipated.
• Quality control and verification: Serving as a benchmark for the performance of engineered structures by validating whether excavation or construction methods impact rock mass behavior.

Reliable use of this test standard helps mitigate design risks and supports regulatory compliance in large-scale construction and infrastructure projects, particularly in variable geological settings.

Related Standards

ASTM D4395-17 is often used alongside or referenced by other key ASTM and international standards, including:

• 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
• ASTM D653 – Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D2113 – Practice for Rock Core Drilling and Sampling of Rock for Site Exploration
• ASTM D4403 – Practice for Extensometers Used in Rock
• ASTM D6026 – Practice for Using Significant Digits in Geotechnical Data
• ASTM D6032 – Test Method for Determining Rock Quality Designation (RQD) of Rock Core
• International Society for Rock Mechanics (ISRM) Suggested Methods

By integrating ASTM D4395-17 with these linked standards, professionals achieve comprehensive site characterization, ensuring the safe design and long-term performance of critical rock engineering projects.

Keywords: ASTM D4395-17, in situ modulus, flexible plate loading method, rock mass deformation, geotechnical field test, civil engineering, underground construction, rock mechanics, displacement measurement, in situ elastic modulus.

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: D4395 − 17
Standard Test Method for
Determining In Situ Modulus of Deformation of Rock Mass
Using Flexible Plate Loading Method
This standard is issued under the fixed designation D4395; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For specific
1.1 This test method covers the preparation, equipment, test
precaution statements, see Section 8.
procedure, and data reduction for determining in situ modulus
1.10 This international standard was developed in accor-
of deformation of a rock mass using the flexible plate loading
dance with internationally recognized principles on standard-
method.
ization established in the Decision on Principles for the
1.2 This test method is designed to be conducted in an adit
Development of International Standards, Guides and Recom-
or small underground chamber; however, with suitable modi-
mendations issued by the World Trade Organization Technical
fications it could be conducted at the surface.
Barriers to Trade (TBT) Committee.
1.3 This test method is usually conducted parallel or per-
2. Referenced Documents
pendicular to the anticipated axis of thrust, as dictated by the
design load and to diametrically opposite surfaces.
2.1 ASTM Standards:
D653Terminology Relating to Soil, Rock, and Contained
1.4 Both instantaneous deformation and primary creep can
Fluids
be obtained from this test method.
D2113Practice for Rock Core Drilling and Sampling of
1.5 Time-dependent tests not covered by this standard can
Rock for Site Exploration
be performed but are to be reported in another standard.
D3740Practice for Minimum Requirements for Agencies
1.6 All observed and calculated values shall conform to the
Engaged in Testing and/or Inspection of Soil and Rock as
guidelines for significant digits and rounding established in Used in Engineering Design and Construction
Practice D6026.
D4394Test Method for Determining In Situ Modulus of
1.6.1 The method used to specify how data are collected, Deformation of Rock Mass Using Rigid Plate Loading
calculated,orrecordedinthisstandardisnotdirectlyrelatedto
Method
theaccuracytowhichthedatacanbeappliedindesignorother
D4403Practice for Extensometers Used in Rock
uses, or both. How one applies the results obtained using this
D4879Guide for Geotechnical Mapping of Large Under-
standard is beyond its scope.
ground Openings in Rock (Withdrawn 2017)
D5079Practices for Preserving andTransporting Rock Core
1.7 Thevaluesstatedininch-poundunitsaretoberegarded
Samples (Withdrawn 2017)
as standard, except as noted below. The values given in
D5434Guide for Field Logging of Subsurface Explorations
parentheses are mathematical conversions to SI units that are
of Soil and Rock
providedforinformationonlyandarenotconsideredstandard.
D6026Practice for Using Significant Digits in Geotechnical
Reporting of test results in units other than SI shall not be
Data
regarded as nonconformance with this test method.
D6032Test Method for Determining Rock Quality Designa-
1.8 Thereferencesappendedtothisstandardcontainfurther
tion (RQD) of Rock Core
information on this test method.
3. Terminology
1.9 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.1 Definitions:
responsibility of the user of this standard to establish appro-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved July 1, 2017. Published August 2017. Originally the ASTM website.
approved in 1984. Last previous edition approved in 2008 as D4395–08. DOI: The last approved version of this historical standard is referenced on
10.1520/D4395-17. www.astm.org.
*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
D4395 − 17
3.1.1 For terminology used in this test method, refer to
Terminology D653.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 deflection, n—movement of the plate, mortar pad, or
rock in response to and in the same direction as the applied
load.
3.2.2 flexible plate, n—theoretically, a plate having no
stiffness.
3.2.3 peak-to-peak modulus of deformation, n—the slope of
FIG. 2 Relationship Between Tangent, Secant, and Recovery
stress-strain curve line connecting the peaks of the curves
Moduli for a Single Loading and Unloading Cycle
obtained from successive pressure cycles (see Fig. 1).
3.2.4 recovery modulus of deformation, n—the tangent
curve judged as the most representative of elastic response by
modulusoftheunloading stress-strain curve.This modulusis
usuallyhigherthantheothermoduliandisusedincalculations the investigator. It neglects the end effects of the curve and is
better suited to small stress changes. The ratio between the
where unloading conditions exist. The difference between the
tangent and recovery moduli indicates the material’s capacity secant modulus and the tangent modulus can be used as a
meansofmeasuringthestressdamageofthematerial(seeFig.
of hysteresis or energy dissipation capabilities (see Fig. 2).
2).
3.2.5 secant modulus of deformation, n—the slope of the
stress-strain curve between zero stress and any specified
4. Summary of Test Method
stress. This modulus should be used for complete load steps
4.1 Areas on two opposing sides of a test adit or under-
from zero to the desired load (see Fig. 2).
ground chamber are made parallel and then flattened and
3.2.6 tangent modulus of deformation, n—the slope of the
smoothed.
stress-strain curve obtained over the segment of the loading
4.2 A hydraulic loading system consisting of flat jacks,
reaction members, and associated hardware is constructed
betweenthetwofacesandamortarpadisplacedoneachface.
4.3 If deflection is to be measured within the rock mass,
installextensometerinstrumentsintherockinaccordancewith
Practice D4403.
4.4 The two faces are loaded and unloaded incrementally
and the deformations of the rock mass at the surfaces and, if
desired, within the rock, are measured after each load and
unload increment. The modulus of deformation (Secant, Tan-
gent and/or Recovery) is then calculated on those segments of
the data plot pertinent to the data acquisition program.
5. Significance and Use
5.1 Results of this type of test method are used to predict
displacementsinrockmasscausedbyloadsfromastructureor
from underground construction. It is one of several tests that
should be performed. The resulting in situ elastic modulus is
commonly less than the elastic modulus determined in the
laboratory.
5.2 The modulus is determined using an elastic solution for
a uniformly distributed load (uniform stress) over a circular
area acting on a semi-infinite elastic medium.
5.3 This test method is normally performed at ambient
temperature, but equipment can be modified or substituted for
operations at other temperatures.
NOTE 1—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
FIG. 1 Rock Surface Deformation as a Function of Bearing Pres- and objective testing/sampling/inspection, etc. Users of this standard are
sure and Increasing Loading Cycles Plot—Arrows show up and cautioned that compliance with Practice D3740 does not in itself assure
down direction of loading cycles line shows Peak to Peak Modu- reliable results. Reliable results depend on many factors; Practice D3740
lus. provides a means of evaluating some of those factors.
D4395 − 17
6. Interferences can invalidate test results when the modulus of rock mass
6 4
exceeds 5×10 psi (3.5×10 MPa).
6.1 The rock under the loaded area is generally not
homogeneous, as assumed in theory. Rock will respond to the
7.5 Loading Equipment—The loading equipment includes
load according to its local deformational characteristics.
the device for applying the load and the reaction members
Therefore, deflection measurements at discrete points on the
(usually thick-walled aluminum or steel pipes) which transmit
rocksurfacetendtobeheavilyinfluencedbythedeformational
the load of sufficient capacity for the intended test program.
characteristics of the rock mass at that location and may give
Flat jacks at each rock face should be used to apply the load
results that are unrepresentative of the rock mass. The use of
and should have sufficient range to allow for deflection of the
the average plate deflection will mitigate this problem.
rock and maintain pressure to within 3%. They should be
constructedsothatthetwomainplatesmoveapartinaparallel
6.2 Measurement of the deflection within the rock mass can
manner over the usable portion of the range. A spherical
utilize a finite gauge length to reflect the average rock mass
bearing of suitable capacity should be incorporated in the
deformation properties between the measuring points. This
reaction members.
approach entails three drawbacks, however. First, the rock
massistestedatverylowstresslevelsunlessthemeasurement
7.6 Load Measuring Instruments—A pressure gauge/
pointsareveryclosetotherocksurfaceandbecauseofthis,the
transducer or load cell should be used to measure the pressure
same problems as with surface measurements occur. Tests at
in the flat jacks. The pressure gauge or transducer should have
low stress levels may give unrealistic modulus values because
an accuracy of at least 620 psi (0.14 MPa), including error
microfractures, joints, and other discontinuities in the rock are
introduced by readout equipment, and a sensitivity of at least
open. Secondly, the disturbance caused by implanting the
10 psi (0.069 MPa). The load cell should have an accuracy of
deflection transducer in the rock mass is difficult to evaluate.
at least 61000 lbf (4.4 kN) including errors introduced by the
The techniques in this test method are designed to produce
readout system, and a sensitivity of at least 500 lbf (2.22 kN)
minimaldisturbance.Thirdly,inrockswithveryhighmodulus,
is recommended.
the accuracy of the instruments may be insufficient to provide
reliable results. 7.7 Bearing Pads—The bearing pad material shall have a
modulus no greater than the modulus of the rock being tested,
6.3 Time-rate of loading has negligible influence on the
as determined from an intact test sample. Generally, a neat
modulus.
cement grout is satisfactory if the curing time does not exceed
6.4 Calculations neglect the stress history of the rock.
several days. Fly ash or other suitable materials may be added
to reduce the stiffness, if necessary.
6.5 This test method is insensitive to Poisson’s ratio, which
must be assumed or obtained from laboratory testing.
8. Safety Precautions
7. Apparatus
8.1 Enforce safety by applicable safety standards.
7.1 Equipmentnecessaryforaccomplishingthistestmethod
includes items for: preparing the test site, drilling and logging 8.2 Pressure lines must be bled of air to preclude violent
failure of the pressure system.
the instrumentation holes, measuring the rock deformation,
applying and restraining test loads, recording test data, and
8.3 Total deformation should not exceed the expansion
transporting various components to the test site.
capabilities of the flat jacks; normally this is approximately
7.2 Test Site Preparation Equipment—This should include
3% of the diameter of a metal flat jack.
an assortment of excavation tools, such as drills, drill bits and
chippinghammers.Blastingshouldnotbeallowedduringfinal
9. In Situ Conditions
preparation of the test site. The drill for the instrumentation
NOTE 2—The guidelines presented in this section are the domain of the
holesshould,ifpossible,havethecapabilityofretrievingcores
agencyororganizationrequestingthetestingandareintendedtofacilitate
from depths of at least 30 ft (10 m). definition of the scope and development of site-specific requirements for
the testing program as a whole.
7.3 Borehole Viewing Device—Some type of device is
9.1 Test each structurally distinctive zone of rock mass
desirable for examination of the instrumentation holes to
selectingareasthataregeologicallyrepresentativeofthemass.
compare and verify geologic features observed in the core if
Test those portions of the rock mass with features such as
core recovery is poor or if it is not feasible to retrieve oriented
faults, fracture zones, cavities, inclusions, and the like to
cores.
evaluatetheireffects.Designthetestingprogramsothateffects
7.4 Deformation Measuring Instruments—Instruments for
of local geology can be clearly distinguished.
measuring deformations should include a reliable multiple
position borehole extensometer (MPBX) for each instrumen- 9.2 The size of the plate will be determined by local
tation hole and a tunnel diameter gauge. For surface geology, pressures to be applied, and the size of the adit to be
measurements, dial gages, or linear variable differential trans- tested. These parameters should be considered prior to exca-
formers (LVDTs) are generally used.An accuracy of at least6 vationoftheadit.Optimumaditdimensionsareapproximately
0.0001 in. (0.0025 mm), including the error of the readout six times the plate diameter; recommended plate diameter is
1 1
equipment, and a sensitivity of at least 0.00005 in. (0.0013 commonly 1 ⁄2 to 3 ⁄4 ft (0.5 to 1 m). Other sizes are used
mm)isrecommended.Errorsinexcessof0.0004in.(0.01mm) depending upon site specifics.
D4395 − 17
9.3 The effects of anisotropy should be investigated by 9.7 Siteconditionsmaydictatethatsitepreparationandpad
appropriately oriented tests: for example, parallel and perpen- construction be performed immediately after excavation.
dicular to the bedding of a sedimentary sequence, or parallel
perpendicular to the long axes of columns in a basalt flow. 10. Procedure
9.4 Tests should be performed at a site not affected by
10.1 Verifythecomplianceofequipmentandapparatuswith
structural changes resulting from excavations of the adit. The
theperformancespecificationsinSection7.Ifrequirementsare
zone of rock that contributes to the measured deflection during
not stated, the manufacturer’s specifications for the equipment
the plate loading test depends on the diameter of the plate and
may be appropriate as a guide, however, care should be taken
the applied load. Larger plates and higher loads measure the
for sufficient performance. Performance verification is gener-
response of rock further away from the test adit. Thus, if the
ally done by calibrating the equipment and measurement
rockaroundtheaditisdamagedbytheexcavationprocess,and
system. Accomplish calibration and documentation in accor-
the deformational properties of the damaged zone are the
dance with the quality assurance procedures in Annex A1.
primary objective of the test program, small-diameter plate
10.2 Ensure that the test results are defensible and traceable
tests on typically excavated surfaces are adequate.
by following at least the minimum guidelines for personnel
9.5 If the rock mass or in situ elastic modulus is desired,
qualifications, calibrations, test setup, test procedure, equip-
larger diameter plates and higher loads may be used, although
ment performance and verification, and vetting of test data are
practical considerations often limit the size of the equipment.
followed in Annex A1.
Alternatively, careful excavation procedures, such as presplit-
10.3 AschematicofanoptimumtestsetupisshownonFig.
ting or other types of smooth-wall blasting, may be employed
3.Aproperly located wooden platform (not shown) allows for
in the test area to limit damage to the rock and the resulting
ease of construction and alignment of all test components.
need for larger plates and loads.
NOTE3—Theprocedureshownisgeneralizedbuttheusershouldnotbe
9.6 Cores, if any, should be logged and tested for rock
confined by this procedure with regards to the actual testing portion. The
quality designation (RQD), fracture spacing, strength, and
user of this standard needs to realize that this is an expensive time
deformationinaccordancewithGuideD5434andTestMethod
consuming test and that running the test is a small part comparted to the
D6032. setup of the test. Therefore, if possible it may be prudent to collect as
FIG. 3 Typical Flexible Plate Bearing Test Setup Schematic in Underground Adit or Tunnel for Testing Horizontally
D4395 − 17
much data as possible before removing the equipment because in most
instances you will not get a second chance to do this test. It is easier to do
this if you have multiple tests and more than one apparatus. For example,
data can be collected at one test site while the next site is being set up.
10.4 Conduct the test across a “diameter” or chord of the
adit with the two test bearing surfaces mutually parallel and in
planes oriented perpendicular to the thrust of the loading
assembly.
10.5 Bearing Surface Preparation:
10.5.1 Method—Prepare the surface by a method that will
cause minimal damage to the finished rock face. Drilling may
be required to reach uniform depth. Residual rock between the
drill holes may be removed by burnishing or moving the bit
backandforthuntilasmoothfaceisachieved.Alternatively,in
hard, competent rock, controlled blasting with very small
FIG. 4 Allowable Dimensions for Rock Surface and Bearing Pad,
charges may be required to remove the residual materials. In
Flexible Plate Loading Test
softer materials, coarse grinding or cutting devices may be
used.
minimum of three equally spaced positions around the edge of
10.5.2 Size—The prepared rock surface should extend at
the opening of the annulus. Secure reference pads to the rock
least one-half the diameter of the flat jack beyond the edge of
surface at surface measurement points. Support the displace-
the jack during the test.
menttransducerssothatonlythedeflectionoftherockitselfis
10.5.3 Rock Quality—Prepare the bearing surface in sound
measured. Generally, this means mounting the transducers
rock. Remove loose and broken rock from the excavation.
from supports located outside the zone of influence of the test.
Deeper breaks may be detected by a dull hollow sound when
In no case should the transducers be mounted on the loading
the rock surface is struck with a hammer; remove such
apparatus. Install cross tunnel measurement points and equip-
material.
ment such as described in Practice D4403.
10.5.4 Smoothness—The prepared rock face should be as
10.8.2 Measurements Within the Rock
...

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: D4395 − 08 D4395 − 17
Standard Test Method for
Determining In Situ Modulus of Deformation of Rock Mass
Using Flexible Plate Loading Method
This standard is issued under the fixed designation D4395; 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*
1.1 This test method covers the preparation, equipment, test procedure, and data reduction for determining in situ modulus of
deformation of a rock mass using the flexible plate loading method.
1.2 This test method is designed to be conducted in an adit or small underground chamber; however, with suitable modifications
it could be conducted at the surface.
1.3 This test method is usually conducted parallel or perpendicular to the anticipated axis of thrust, as dictated by the design
load.load and to diametrically opposite surfaces.
1.4 Both instantaneous deformation and primary creep can be obtained from this test method.
1.5 Time-dependent tests not covered by this standard can be performed but are to be reported in another standard.
1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice
D6026.
1.6.1 The method used to specifiyspecify how data are collected, calculated, or recorded in this standard is not directly related
to the accuracy to which the data can be applied in design or other uses, or both. How one applies the results obtained using this
standard is beyond its scope.
1.7 The values stated in inch-pound units are to be regarded as standard. standard, except as noted below. The values given in
parentheses are mathematical conversions to SI units that 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 test method.
1.8 The references appended to this standard contain further information on this test method.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. For specific precaution statements, see Section 8.
1.10 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
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4394 Test Method for Determining In Situ Modulus of Deformation of Rock Mass Using Rigid Plate Loading Method
D4403 Practice for Extensometers Used in Rock
D4879 Guide for Geotechnical Mapping of Large Underground Openings in Rock (Withdrawn 2017)
This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
Current edition approved July 1, 2008July 1, 2017. Published July 2008August 2017. Originally approved in 1984. Last previous edition approved in 20042008 as
D4395 – 04.D4395 – 08. DOI: 10.1520/D4395-08.10.1520/D4395-17.
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.
The last approved version of this historical standard is referenced on www.astm.org.
*A Summary of Changes section appears at the end of this standard
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D5079 Practices for Preserving and Transporting Rock Core Samples (Withdrawn 2017)
D5434 Guide for Field Logging of Subsurface Explorations of Soil and Rock
D6026 Practice for Using Significant Digits in Geotechnical Data
D6032 Test Method for Determining Rock Quality Designation (RQD) of Rock Core
3. Terminology
3.1 For terminology used in this test method, refer to Terminology D653.Definitions:
3.1.1 For terminology used in this test method, refer to Terminology D653.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 deflection—deflection, n—movement of the plate, mortar pad, or rock in response to and in the same direction as the
applied load.
3.2.2 flexible plate—plate, n—theoretically, a plate having no stiffness.
3.2.3 load—total force acting on the rock face.
3.2.3 peak-to-peak modulus of deformation—deformation, n—the slope of stress - strain curve line connecting the peaks of the
curves obtained from successive pressure cycles (see Fig. 1).
3.2.4 recovery modulus of deformation—deformation, n—the tangent modulus of the unloading stress - strain curve. This
modulus is usually higher than the other moduli and is used in calculations where unloading conditions exist. The difference
between the tangent and recovery moduli indicates the material’s capacity of hysteresis or energy dissipation capabilities (see Fig.
2).
3.2.5 secant modulus of deformation—deformation, n—the slope of the stress - strain curve between zero stress and any
specified stress. This modulus should be used for complete load steps from zero to the desired load (see Fig. 2).
3.2.6 tangent modulus of deformation—deformation, n—the slope of the stress - strain curve obtained over the segment of the
loading curve judged as the most representative of elastic response by the investigator. It neglects the end effects of the curve and
FIG. 1 Rock Surface Deformation as a Function of Bearing Pressure and Increasing Loading Cycles Plot—Arrows show up and down
direction of loading cycles line shows Peak to Peak Modulus.
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FIG. 2 Relationship Between Tangent, Secant, and Recovery Moduli for a Single Loading and Unloading Cycle
is better suited to small stress changes. The ratio between the secant modulus and the tangent modulus can be used as a means
of measuring the stress damage of the material (see Fig. 2).
4. Summary of Test Method
4.1 Areas on two opposing parallel faces sides of a test adit are or underground chamber are made parallel and then flattened
and smoothed.
4.2 A hydraulic loading system consisting of flatjacks, flat jacks, reaction members, and associated hardware is constructed
between the two faces and a mortar pad is placed on each face.
4.3 If deflection is to be measured within the rock mass, install extensometer instruments in the rock in accordance with Practice
D4403.
4.4 The two faces are loaded and unloaded incrementally and the deformations of the rock mass at the surfaces and, if desired,
within the rock, are measured after each load and unload increment. The modulus of deformation is then calculated.(Secant,
Tangent and/or Recovery) is then calculated on those segments of the data plot pertinent to the data acquisition program.
5. Significance and Use
5.1 Results of this type of test method are used to predict displacements in rock mass caused by loads from a structure or from
underground construction. It is one of several tests that should be performed. The resulting in situ elastic modulus is commonly
less than the elastic modulus determined in the laboratory.
5.2 The modulus is determined using an elastic solution for a uniformly distributed load (uniform stress) over a circular area
acting on a semi-infinite elastic medium.
5.3 This test method is normally performed at ambient temperature, but equipment can be modified or substituted for operations
at other temperatures.
NOTE 1—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 rock under the loaded area is generally not homogeneous, as assumed in theory. Rock will respond to the load according
to its local deformational characteristics. Therefore, deflection measurements at discrete points on the rock surface tend to be
heavily influenced by the deformational characteristics of the rock mass at that location and may give results that are
unrepresentative of the rock mass. The use of the average plate deflection will mitigate this problem.
6.2 Measurement of the deflection within the rock mass can utilize a finite gauge length to reflect the average rock mass
deformation properties between the measuring points. This approach entails three drawbacks, however. First, the rock mass is
tested at very low stress levels unless the measurement points are very close to the rock surface and because of this, the same
problems as with surface measurements occur. Tests at low stress levels may give unrealistic modulus values because
microfractures, joints, and other discontinuities in the rock are open. Secondly, the disturbance caused by implanting the deflection
transducer in the rock mass is difficult to evaluate. The techniques in this test method are designed to produce minimal disturbance.
Thirdly, in rocks with very high modulus, the accuracy of the instruments may be insufficient to provide reliable results.
6.3 Time-rate of loading has negligible influence on the modulus.
6.4 Calculations neglect the stress history of the rock.
6.5 This test method is insensitive to Poisson’s ratio, which must be assumed or obtained from laboratory testing.
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7. Apparatus
7.1 Equipment necessary for accomplishing this test method includes items for: preparing the test site, drilling and logging the
instrumentation holes, measuring the rock deformation, applying and restraining test loads, recording test data, and transporting
various components to the test site.
7.2 Test Site Preparation Equipment—This should include an assortment of excavation tools, such as drills drills, drill bits and
chipping hammers. Blasting should not be allowed during final preparation of the test site. The drill for the instrumentation holes
should, if possible, have the capability of retrieving cores from depths of at least 30 ft (10 m).
7.3 Borehole Viewing Device—Some type of device is desirable for examination of the instrumentation holes to compare and
verify geologic features observed in the core if core recovery is poor or if it is not feasible to retrieve oriented cores.
7.4 Deformation Measuring Instruments—Instruments for measuring deformations should include a reliable multiple position
borehole extensometer (MPBX) for each instrumentation hole and a tunnel diameter gauge. For surface measurements, dial gages,
or linear variable differential transformers (LVDTs) are generally used. An accuracy of at least6 0.0001 in. (0.0025 mm), including
the error of the readout equipment, and a sensitivity of at least 0.00005 in. (0.0013 mm) is recommended. Errors in excess of
6 4
0.0004 in. (0.01 mm) can invalidate test results when the modulus of rock mass exceeds 5 × 10 psi (3.5 × 10 MPa).
7.5 Loading Equipment—The loading equipment includes the device for applying the load and the reaction members (usually
thick-walled aluminum or steel pipes) which transmit the load. Flatjacks load of sufficient capacity for the intended test program.
Flat jacks at each rock face should be used to apply the load and should have sufficient range to allow for deflection of the rock
and maintain pressure to within 3 %. They should be constructed so that the two main plates move apart in a parallel manner over
the usable portion of the range. A spherical bearing of suitable capacity should be incorporated in the reaction members.
7.6 Load Measuring Instruments—A pressure gauge/transducer or load cell should be used to measure the pressure in the
flatjacks. flat jacks. The pressure gauge or transducer should have an accuracy of at least 620 psi (0.14 MPa), including error
introduced by readout equipment, and a sensitivity of at least 10 psi (0.069 MPa). The load cell should have an accuracy of at least
61000 lbf (4.4 kN) including errors introduced by the readout system, and a sensitivity of at least 500 lbf (2.22 kN) is
recommended.
7.7 Bearing Pads—The bearing pad material shall have a modulus no greater than the modulus of the rock being tested, as
determined from an intact test sample. Generally, a neat cement grout is satisfactory if the curing time does not exceed several days.
Fly ash or other suitable materials may be added to reduce the stiffness, if necessary.
8. Safety Precautions
8.1 All personnel involved in performing the test should be formally pre-qualified in accordance with the quality assurance
procedures of Enforce safety by applicable safety standards.Annex A1.
8.2 Verify the compliance of all equipment and apparatus with the performance specifications in Section Pressure lines 7. If no
requirements are stated, the manufacturer’s specifications for the equipment may be appropriate as a guide, but care must be taken
for sufficient performance. Performance verification is generally done by calibrating the equipment and measurement system.
Accomplish calibration and documentation in accordance with must be bled of air to preclude violent failure of the pressure
system.Annex A1.
8.3 Enforce safety by applicable safety standards. Pressure lines must be bled of air to preclude violent failure of the pressure
system. Total deformation should not exceed the expansion capabilities of the flatjacks; flat jacks; normally this is approximately
3 % of the diameter of a metal flatjack.flat jack.
9. In Situ Conditions
NOTE 2—The guidelines presented in this section are the domain of the agency or organization requesting the testing and are intended to facilitate
definition of the scope and development of site-specific requirements for the testing program as a whole.
9.1 Test each structurally distinctive zone of rock mass selecting areas that are geologically representative of the mass. Test
those portions of the rock mass with features such as faults, fracture zones, cavities, inclusions, and the like to evaluate their
affects.effects. Design the testing program so that affectseffects of local geology can be clearly distinguished.
9.2 The size of the plate will be determined by local geology, pressures to be applied, and the size of the adit to be tested. These
parameters should be considered prior to excavation of the adit. Optimum adit dimensions are approximately six times the plate
1 1
diameter; recommended plate diameter is commonly 1 ⁄2 to 3 ⁄4 ft (0.5 to 1 m). Other sizes are used depending upon site specifics.
9.3 The effects of anisotropy should be investigated by appropriately oriented tests: for example, parallel and perpendicular to
the bedding of a sedimentary sequence, or parallel perpendicular to the long axes of columns in a basalt flow.
9.4 Tests should be performed at a site not affected by structural changes resulting from excavations of the adit. The zone of
rock that contributes to the measured deflection during the plate loading test depends on the diameter of the plate and the applied
load. Larger plates and higher loads measure the response of rock further away from the test adit. Thus, if the rock around the adit
is damaged by the excavation process, and the deformational properties of the damaged zone are the primary objective of the test
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program, small-diameter plate tests on typically excavated surfaces are adequate. If the undisturbed in situ modulus is desired,
larger diameter plates and higher loads may be used, although practical considerations often limit the size of the equipment.
Alternatively, careful excavation procedures, such as presplitting or other types of smooth-wall blasting, may be employed in the
test area to limit damage to the rock and the resulting need for larger plates and loads.
9.5 If the rock mass or in situ elastic modulus is desired, larger diameter plates and higher loads may be used, although practical
considerations often limit the size of the equipment. Alternatively, careful excavation procedures, such as presplitting or other types
of smooth-wall blasting, may be employed in the test area to limit damage to the rock and the resulting need for larger plates and
loads.
9.6 Cores, if any, should be logged and tested for rock quality designation (RQD), fracture spacing, strength, and deformation
in accordance with Guide D5434 and Test Method D6032.
9.7 Site conditions may dictate that site preparation and pad construction be performed immediately after excavation.
10. Procedure
10.1 Verify the compliance of equipment and apparatus with the performance specifications in Section 7. If requirements are
not stated, the manufacturer’s specifications for the equipment may be appropriate as a guide, however, care should be taken for
sufficient performance. Performance verification is generally done by calibrating the equipment and measurement system.
Accomplish calibration and documentation in accordance with the quality assurance procedures in Annex A1.
10.2 Ensure that the test results are defensible and traceable by following at least the minimum guidelines for personnel
qualifications, calibrations, test setup, test procedure, equipment performance and verification, and vetting of test data are followed
in Annex A1.
10.3 A schematic of an optimum test setup is shown on Fig. 3. A properly located wooden platform (not shown) allows for ease
of construction and alignment of all test components.
NOTE 3—The procedure shown is generalized but the user should not be confined by this procedure with regards to the actual testing portion. The user
of this standard needs to realize that this is an expensive time consuming test and that running the test is a small part comparted to the setup of the test.
Therefore, if possible it may be prudent to collect as much data as possible before removing the equipment because in most instances you will not get
a second chance to do this test. It is easier to do this if you have multiple tests and more than one apparatus. For example, data can be collected at one
test site while the next site is being set up.
10.4 Conduct the test across a “diameter” or chord of the adit with the two test bearing surfaces mutually parallel and in planes
oriented perpendicular to the thrust of the loading assembly.
FIG. 3 Typical Flexible Plate Bearing Test Setup Schematic in Underground Adit or Tunnel for Testing Horizontally
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10.5 Bearing Surface Preparation : Preparation:
10.5.1 Method—Prepare the surface by a method that will cause minimal damage to the finished rock face. Drilling may be
required to reach uniform depth. Residual rock between the drill holes may be removed by burnishing or moving the bit back and
forth until a smooth face is achieved. Alternatively, in hard, competent rock, controlled blasting with very small charges may be
required to remove the residual materials. In softer materials, coarse grinding or cutting devices may be used.
10.5.2 Size—The prepared rock surface should extend at least one-half the diameter of the flatjack flat jack beyond the edge of
the jack during the test.
10.5.3 Rock Quality—Prepare the bearing surface in sound rock. Remove loose and broken rock from the excavation. Deeper
breaks may be detected by a dull hollow sound when the rock surface is struck with a hammer; remove such material.
10.5.4 Smoothness—The prepared rock face should be as smooth as practicable. In no case should the deviation from a plane
between the highest and lowest points exceed 1 in. (25 mm).
10.5.5 Cleaning—After the surface has been prepared, scrub and rinse it with clean water to remove any loose particles or dirt
caused by the smoothing operation.
10.6 Map the geology of the test bearing surfaces and test site, both in plan and cros
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