ASTM D4971-89(1998)
(Test Method)Standard Test Method for Determining the In Situ Modulus of Deformation of Rock Using the Diametrically Loaded 76-mm (3-in.) Borehole Jack
Standard Test Method for Determining the In Situ Modulus of Deformation of Rock Using the Diametrically Loaded 76-mm (3-in.) Borehole Jack
SCOPE
1.1 This test method covers the estimation of in situ modulus of a rock mass at various depths and orientations. Information on time-dependent deformation may also be obtained.
1.2 The values stated in SI units are regarded as standard. The inch-pound units in parentheses are for information only.
1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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.
General Information
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Standards Content (Sample)
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Designation: D 4971 – 89 (Reapproved 1998)
Standard Test Method for
Determining the In Situ Modulus of Deformation of Rock
Using the Diametrically Loaded 76-mm (3-in.) Borehole
Jack
This standard is issued under the fixed designation D 4971; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the estimation of in situ
modulus of a rock mass at various depths and orientations.
Information on time-dependent deformation may also be ob-
tained.
1.2 The values stated in SI units are regarded as standard.
The inch-pound units in parentheses are for information only.
1.3 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 appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D 653 Terminology Relating to Soil, Rock and Contained
Fluids
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 deformation—change in shape or size, (see Terminol-
ogy D 653). In this test method deformation is the change in
the diameter of the borehole.
3.1.2 modulus of deformation—ratio of stress to strain for a
material under given loading conditions; numerically equal to
the slope of the tangent or the secant of the stress-strain curve.
The use of the term modulus of elasticity is recommended for
materials that deform in accordance with Hooke’s law, and the
term modulus of deformation is recommended for materials
that deform otherwise, (see Terms D 653). In this test method,
the modulus of deformation is calculated from the applied fluid
pressure, the relative change in hole diameter, a function of
Poisson’s ratio, and a constant.
4. Summary of Test Method
4.1 The 76 mm (3.0 in.) jacks, (see Fig. 1 and Fig. 2), induce
undirectional pressure to the walls of a borehole by means of
FIG. 1 The 76-mm (3-in.) Borehole Jack
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
and Rock and is the direct responsibility of Subcommittee D18.12 on Rock
two opposed curved steel platens each covering a 90° sector,
Mechanics.
over a length of 20.3 cm (8 in.).
Current edition approved July 28, 1989. Published October 1989.
Annual Book of ASTM Standards, Vol 04.08. 4.2 Raw data from a test consist of hydraulic-line pressure,
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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D 4971
that the calculated modulus values can decrease by up to 29 %.
Therefore, tensile cracking would result in a decrease in the
slope of the loading curve and test data in the region of
decreased slope should not be used.
6.2 The volume of rock mass involved in the 76 mm (3.0
in.) diameter jack test has been estimated (2) to be about 0.15
3 3
m (5 ft ). This volume may not include enough discontinuities
to be representative of the rock mass on a larger scale.
6.3 Two aspects of jack behavior, discussed in 6.3.1 and
6.3.2, require careful consideration in the analysis of test data
and can be compensated for by the procedure outlined in this
test method and detailed by Heuze and Amadei (3).
6.3.1 The platen/rock contact may not cover 90° of the
borehole circumference, as assumed, because of radius mis-
FIG. 2 Schematic of Loading of the Borehole Jack
match between the jack and the hole (4, 5).
6.3.2 In rock with modulus of deformation greater than
Q , versus readout from linear variable differential transform-
h
about 7 GPa (10 psi), there is a longitudinal concave outward
ers (LVDT’s) measuring platen movement. Knowing the dis-
bending of the jack platens that requires correction. This
placement calibration of the LVDT’s, the raw data can be
correction is necessary because the bending gives higher
transformed to a test record of hydraulic pressure versus hole
displacements at the ends than at the center of the loading
diameter, D. For each increment of pressure, DQ , and hole
h
platens and LVDT displacement gages are located near the
deformation, DD, theoretical data analysis (1), assuming rigid
ends of the platens.
jack plates and full 90° contact, give the theoretical rock mass
modulus, E (E ) as a function E 5 f (D Q ·DD· T*),
theoretical h
7. Apparatus
where T* is a coefficient dependent upon Poisson’s ratio. If E
7.1 Borehole Jack—The borehole jack for which equations
is measured on a linear segment of the loading curve, common
and corrections are presented in Section 12 is the so-called
terminology is modulus of deformation. If E is measured on an
“hard rock” jack, that is currently manufactured under patent.
unloading linear segment, it is referred to as the recovery
The manufacturer’s specifications are: range of travel is 13 mm
modulus.
(0.5 in.) from closed at 70 mm (2.75 in.) to fully open at 83 mm
(3.25 in.), maximum pressure on borehole wall is 64 MPa
5. Significance and Use
(9300 psi), and deformation resolution is 0.025 mm (0.001 in.).
5.1 Results of this test method are used to predict displace-
The maximum jack pressure is achieved with a hydraulic
ments in rock mass caused by loads from a structure or from
system pressure of 69 MPa (10 000 psi). Deformation is
underground construction. It is one of several tests that should
measured by an LVDT at each end of the loading platens.
be performed.
These are referred to as the near and far LVDT respectively.
5.2 Because the jack can apply directed loads, this test
7.2 Pressure Gage—A hydraulic gage or electronic trans-
method can be performed to provide an estimate of anisotropy.
ducer may be used to measure the hydraulic system pressure.
5.3 In theory, the analysis of test data is straight forward; the
The gage shall have an accuracy of at least 280 kPa (40 psi),
modulus estimate requires a record of applied hydraulic
including errors introduced by the readout equipment, and a
pressure versus borehole diameter change, and a knowledge of
resolution of at least 140 kPa (20 psi).
the rock’s Poisson’s ratio. In practice, the above procedure,
7.3 Casing Alignment System—The borehole jack is at-
using the original theoretical formula, frequently has resulted
tached to 73 mm (2.875 in.) BX drill casing and placed into
in computing a material modulus that was demonstrably too
position in the borehole. To determine the orientation of the
low.
jack, an orientation mark is transferred to successive sections
5.4 For analyzing the test data it is assumed that the rock
of casing as they are added. To avoid introducing a systematic
mass is linearly elastic, isotropic, and homogeneous. Within
and progressive error into orientation, an alignment device
these assumptions, this test method can provide useful data for
shall be used to transfer the mark from one casing section to
rock masses for which equivalent continuous properties can not
another. In vertical boreholes, a plumb line may be sufficient.
be found or estimated.
In inclined or horizontal boreholes, a marking guide such as the
one shown on Fig. 3 has been found satisfactory (6).
6. Interferences
6.1 It is assumed that the tensile and compressive moduli of
8. Sampling, Test Specimens, and Test Units
the rock are equal and there is not tensile cracking induced in
8.1 Number and Orientation of Boreholes—The number,
the rock mass because of jack loading. If tensile cracks are
spacing, and orientation of boreholes depend on the geometry
created at 90° to the loading direction, it has been shown (1)
of the project and the geology of the site.
8.2 Rock Sampling:
8.2.1 Each type of rock should be tested. In addition, areas
The boldface numbers in parentheses refer to a list of references at the end of
the standard. of low modulus of deformation, such as fracture or alteration
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4971
equivalent directions (7). In addition, the jack shall be cali-
brated during the test program if the program consists of many
tests or if the deformation readings become suspect. This is
particularly likely if the difference in the readings of near and
far LVDT’s exceeds the manufacturer’s recommendation of 0.5
mm (0.02 in.), indicating excessive misalignment of the
platens.
10.2 Calibration of the boreholes jack must be documented.
Personnel using the equipment must be qualified in advance.
11. Procedure
11.1 Test each distinctive rock material in a borehole.
11.2 Testing Discontinuities—Locate tests in both intact
FIG. 3 Marking Guide on Section of Casing
zones and fractured zones to evaluate the effects of disconti-
nuities. If the two LVDT’s give significantly different displace-
zones within a rock mass, are of particular interest and should
ment ($0.5 mm or 0.02 in.), discard the data and relocate the
be tested.
jack.
8.2.2 Tests should be conducted at different orientations to
11.3 Boreholes—Boreholes shall be free from dirt and drill
sample the anistropy of the rock mass, for example, parallel
cuttings. Wash the borehole with clean water if necessary.
and perpendicular to the long axes of the columns in a basalt
11.4 Initial Seating Pressure—When the jack is at the test
flow. Boreholes should generally be orthogonal to each other
location and in the desired orientation, raise the hydraulic
and either parallel or perpendicular to the structure of the rock
pressure to 350 kPa (50 psi) to seat the platens against the
formation. At least ten tests in each rock material are recom-
borehole wall. Use this pressure as the “zero” pressure
mended.
throughout the remainder of the test.
8.3 Boreholes Reamed—It is recommended that a reaming
11.5 Pressure Level—Test the rock to a pressure in excess
shell with a nominal outside diameter of 76 mm (3 in.) be used.
of that required for full platen contact, but not exceeding the
It is further recommended that a bit fabricated to reaming shell
pressure or displacement capacity of the jack. Failure of the
gage 76 mm (3 in.) also be used. This will minimize the radius
rock may be recognized by an increase in the rate of deforma-
mismatch between the borehole and the jack. Accurate mea-
tion without corresponding increase in the rate of pressure.
surement of the diameter of the borehole is important.
11.6 Pressure Cycles—In at least 25 % of the tests in each
8.4 Boreholes Cored—The boreholes shall be drilled using
rock material, conduct multiple-pressure cycling to progres-
diamond core techniques; continuous core should be obtained.
sively higher loads to evaluate permanent deformation and the
Oriented cores are desirable but not mandatory.
effects of cycling on modulus. The peak pressure shall be
8.5 Core Logged—The recovered core should be com-
approximately 30, 60, and 100 % of the maximum. During
pletely logged, with emphasis on fractures and other mechani-
each cycle, vary the pressure in at least five equal increments
cal inhomogeneties and water pressure. Rock quality designa-
and five decrements. At the end of each cycle, return the
tion (RQD) should be calculated for each 1.5 m (5 ft) of hole
pressure to the initial seating pressure.
cored or core run.
11.7 Test at Various Orientations—If tests are desired in
8.6 Test Location—Within each borehole, locations for each
different orientations, it is preferable to move the jack at least
test should be selected based on the core logs. In some cases
30.5 cm (12 in.) below or above the previous test location so as
observation of the borehole with a borescope or borehole
to provide an undisturbed site for testing. It is suggested that
camera (film or television) may be useful.
successive orientations be perpendicular to each other. It is
recommended that the first test be conducted at the deepest
9. Personnel and Equipment Requirements
location, and the following tests be at successively shallower
9.1 Personnel—All personnel involved in performing the
depths to prevent possible borehole damage in a given test
test, including technicians and test supervisors, should be under
from interfering with subsequent testing.
the guidance of someone thoroughly familiar with the use of
11.8 Indications of Time-Dependent Effects—Determine
the jack. Sometimes the personnel may be required to be
time dependent deformation characteristics during the test by
formally pre-qualified under a quality assurance (QA) proce-
maintaining the maximum test pressure for 15 min and
dures established as part of the overall testing program.
recording deformation at 5 min intervals. When the pressure is
9.2 Equipment Performance Verification— The compliance
reduced to the initial seating pressure, take deformation read-
of all equipment and apparatus with performance specifications
ings again at 5 min intervals for 15 min. If at least three such
of this procedure shall be verified. Performance verification is
determinations are made in a given rock material, and the
generally done by calibrating the equipment and measurement
deformation indicated by either LVDT changing by more than
systems according to established procedures.
5 % of the total accumulated deformation up to that stress level
over the 15 min intervals in any of the tests, assume that the
10. Calibration
material exhibits time-dependent behavior at that stress level,
10.1 The borehole jack shall be calibrated before and at the and, follow by further investigation.
completion of the program according to manufacturer’s or 11.9 Data Recording Requirements—Record the data
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4971
TABLE 1 Minimum Hydraulic Pressure to Ensure Full Contact as
A
a Function of Hole Radius Mismatch a with n 5 0.25
E Q min/a
theoretical h
6 −3
10 psi GPa psi/10 in. MPa/mm
Oversize Holes (inch-pound units):
0.20 a30 3 10 E
theoretical
B
Q min 5
h 6 2
30 3 10 12n 1 0.91 E
~ !
theoretical
1 6.9 200 55
2 13.8 400 110
3 20.7 580 160
4 27.6 750 205
5 34.5 920 250
6 41.4 1070 290
7 48.3 1210 330
8 55.2 1350 370
9 62.1 1480 400
10 69.0 1600 440
aE
theoretical
C
Undersized Holes (inch/pound units): Q min 5
h
...
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