ASTM D4554-02(2006)
(Test Method)Standard Test Method for In Situ Determination of Direct Shear Strength of Rock Discontinuities
Standard Test Method for In Situ Determination of Direct Shear Strength of Rock Discontinuities
SIGNIFICANCE AND USE
Because of scale effects, there is no simple method of predicting the in situ shear strength of a rock discontinuity from the results of laboratory tests on small specimens; in situ tests on large specimens are the most reliable means.
Results can be employed in stability analysis of rock engineering problems, for example, in studies of slopes, underground openings, and dam foundations. In applying the test results, the pore water pressure conditions and the possibility of progressive failure must be assessed for the design case, as they may differ from the test conditions.
Tests on intact rock (free from planes of weakness) are usually accomplished using laboratory triaxial testing. Intact rock can, however, be tested in situ in direct shear if the rock is weak and if the specimen block encapsulation is sufficiently strong.
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 D 3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D 3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D 3740 provides a means of evaluating some of those factors.
SCOPE
1.1 This test method covers the measurement of peak and residual direct shear strength of in situ rock discontinuities as a function of stress normal to the sheared plane. This sheared plane is usually a significant discontinuity which may or may not be filled with gouge or soil-like material.
1.2 The measured shear properties are affected by scale factors. The severity of the effect of these factors must be assessed and applied to the specific problems on an individual basis.
1.3 The values stated in SI units are to be regarded as the standard.
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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D4554 − 02(Reapproved 2006)
Standard Test Method for
In Situ Determination of Direct Shear Strength of Rock
Discontinuities
This standard is issued under the fixed designation D4554; 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* 3.2.2 peak shear strength—the maximum shear stress in the
complete curve of stress versus displacement obtained for a
1.1 This test method covers the measurement of peak and
specified constant normal stress.
residual direct shear strength of in situ rock discontinuities as
a function of stress normal to the sheared plane. This sheared 3.2.3 residual shear strength—the shear stress at which
nominally no further rise or fall in shear strength is observed
plane is usually a significant discontinuity which may or may
not be filled with gouge or soil-like material. with increasing shear displacement and constant normal stress
(Fig. 1). A true residual strength may only be reached after
1.2 The measured shear properties are affected by scale
considerably greater shear displacement than can be achieved
factors. The severity of the effect of these factors must be
in testing. The test value should be regarded as approximate
assessed and applied to the specific problems on an individual
and should be assessed in relation to the complete shear stress
basis.
- displacement curve.
1.3 The values stated in SI units are to be regarded as the
3.2.4 shear strength parameter, c (see Fig. 2) —the pro-
standard.
jected intercept on the shear stress axis of the plot of shear
1.4 This standard does not purport to address all of the
stress versus normal stress (see Note).
safety concerns, if any, associated with its use. It is the
3.2.5 shear strength parameter, φ (see Fig. 2) —the angle of
responsibility of the user of this standard to establish appro-
the tangent to the failure curve at a normal stress that is
priate safety and health practices and determine the applica-
relevant to design.
bility of regulatory limitations prior to use.
3.2.5.1 Discussion—Different values of c and φ relate to
2. Referenced Documents different stages of a test (for example, c`, c `, φ , and φ,of
r a b
Fig. 2).
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained
4. Summary of Test Method
Fluids
D3740 Practice for Minimum Requirements for Agencies
4.1 This test method is performed on rectangular-shaped
Engaged in Testing and/or Inspection of Soil and Rock as
blocks of rock that are isolated on all surfaces, except for the
Used in Engineering Design and Construction
shear plane surface.
4.2 The blocks are not to be disturbed during preparation
3. Terminology
operations.Thebaseoftheblockcoincideswiththeplanetobe
3.1 Definitions—See Terminology D653 for general defini-
sheared.
tions.
4.3 A normal load is applied perpendicular to the shear
3.2 Definitions of Terms Specific to This Standard:
plane and then a side load is applied to induce shear along the
3.2.1 discontinuities—thisincludesjoints,schistosity,faults,
plane and discontinuity (see Fig. 3).
bedding planes, cleavage, and zones of weakness, along with
any filling material.
5. Significance and Use
5.1 Because of scale effects, there is no simple method of
This test method is under the jurisdiction ofASTM Committee D18 on Soil and
Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.
predicting the in situ shear strength of a rock discontinuity
Current edition approved May 1, 2006. Published June 2006. Originally
from the results of laboratory tests on small specimens; in situ
approved in 1985. Last previous edition approved in 2002 as D4554 – 02. DOI:
tests on large specimens are the most reliable means.
10.1520/D4554-02R06.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2 Results can be employed in stability analysis of rock
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
engineering problems, for example, in studies of slopes,
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. underground openings, and dam foundations. In applying the
*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
D4554 − 02 (2006)
FIG. 1 Shear Stress – Displacement Graphs
hydraulic rams are used for loading, care is needed to ensure that their
test results, the pore water pressure conditions and the possi-
operating characteristics are identically matched and they are in exact
bility of progressive failure must be assessed for the design
parallel alignment.
case, as they may differ from the test conditions.
6.2.1 Each ram should be provided with a spherical seat.
5.3 Tests on intact rock (free from planes of weakness) are
The travel of rams, and particularly of flat jacks, should be
usually accomplished using laboratory triaxial testing. Intact
sufficient to accommodate the full anticipated specimen dis-
rock can, however, be tested in situ in direct shear if the rock
placement. The normal displacement may be estimated from
is weak and if the specimen block encapsulation is sufficiently
the content and thickness of the filling and roughness of the
strong.
shear surfaces. The upper limits would be the filling thickness.
NOTE 1—The quality of the result produced by this standard is
6.2.2 Hydraulic System—A hydraulic system, if used,
dependent on the competence of the personnel performing it, and the
suitability of the equipment and facilities used. Agencies that meet the
should be capable of maintaining a normal load to within 2 %
criteria of Practice D3740 are generally considered capable of competent
of a selected value throughout the test.
and objective testing/sampling/inspection/etc. Users of this standard are
6.2.3 Reaction System—A reaction system to transfer nor-
cautioned that compliance with Practice D3740 does not in itself assure
mal loads uniformly to the test block includes rollers or a
reliable results. Reliable results depend on many factors; Practice D3740
provides a means of evaluating some of those factors. similar low friction device to ensure that at any given normal
load, the resistance to shear displacement is less than 1 % of
6. Apparatus
the maximum shear force applied in the test. Rock anchors,
wire ties, and turnbuckles are usually required to install and
6.1 Equipment for Cutting and Encapsulating the Test
secure the equipment.
Block—This includes rock saws, drills, hammer and chisels,
formwork of appropriate dimensions and rigidity, expanded
6.3 Equipment for Applying the Shear Force (see Fig. 3):
polystyrenesheetingorweakfiller,andmaterialsforreinforced
6.3.1 One or More Hydraulic Rams , of adequate total
concrete encapsulation.
capacity with at least 150-mm travel.
6.2 Equipment for Applying the Normal Load (see Fig.
6.3.2 Hydraulic Pump, to pressurize the shear force system.
3)—This includes flat jacks, hydraulic rams, or dead load of
6.3.3 Reaction System—A reaction system to transmit the
sufficient capacity to apply the required normal loads.
shear force to the test block. The shear force should be
distributed uniformly along one face of the specimen. The
NOTE 2—If a dead load is used for normal loading, precautions are
required to ensure accurate centering and stability. If two or more resultant line of applied shear forces should pass through the
D4554 − 02 (2006)
NOTE 1—In this case, intercept c on shear axis is zero.
r
f = residual friction angle,
r
f = apparent friction angle below stress s ; point A is a break in the peak shear strength curve resulting from the shearing off of major irregularities on the
a a
shear surface. Between points O and A, f will vary somewhat; measure at stress level of interest. Note also that f = f + i where:
a a u
f = friction angle obtained for smooth surfaces of rock on rock, and
u
i = inclination angle of surface asperities.
f = apparent friction angle above stress level s (Point A); note that f will usually be equal to or slightly greater than f and will vary somewhat with
b a a r
stress level; measure at the stress level of interest, r.
c8 = cohesion intercept of peak shear strength curve; it may be zero.
c = apparent cohesion at a stress level corresponding to f , and
b
c = cohesion intercept of residual shear strength which is usually negligible.
r
FIG. 2 Shear Strength – Effective Normal Stress Graph
FIG. 3 Typical Arrangement of Equipment for In Situ Direct Shear Test
D4554 − 02 (2006)
center of the base of the shear plane at an angle approximately load to the upper face of the test specimen as soon as possible
15° to the shear plane with an angular tolerance of6 5°. The after excavation of the opening and prior to sawing the sides.
exact angle should be measured to 61°. The load, approximately equal to the overburden pressure,
may, for example, be provided by screw props or a system of
NOTE 3—Tests where both shear and normal forces are provided by a
rock bolts and crossbeams. Maintain the load until the test
single set of jacks inclined at greater angles to the shear plane are not
equipment is in position. Saw the test block to the required
recommended, as it is then impractical to control shear and normal
stresses independently.
dimensions (usually 700 by 700 by 350 mm) using methods
that avoid disturbance or loosening of the block. Saw a channel
6.4 Equipment for Measuring the Applied Force—This in-
approximately 200 mm deep by 80 mm wide around the base
cludes one system for measuring normal force and another for
of the block to allow freedom of displacements during testing.
measuring applied shearing force with an accuracy better than
The block and particularly the shear plane should, unless
62 % of the maximum forces reached in the test. Load cells
otherwise specified, be retained as close as possible to its
(dynamometers) or flat jack pressure measurements may be
natural in situ conditions during preparation and testing.
used. Recent calibration data applicable to the range of testing
should be appended to the test report. If possible, the gages
NOTE 5—A test block size of 700 by 700 by 350 mm is suggested as
should be calibrated both before and after testing.
standardforinsitutesting.Smallerblocksarepermissible,if,forexample,
the surface to be tested is relatively smooth; larger blocks may be needed
6.5 Equipment for Measuring Shear, Normal, and Lateral
when testing very irregular surfaces. For convenience, the size and shape
Displacement—Displacement should be measured (for ex-
of the test block may be adjusted so that the faces of the block coincide
ample, using micrometer dial gages) at eight locations on the
with joints or fissures. This adjustment minimizes block disturbance
specimen block or encapsulating material, as shown in Fig. 4 during preparation. Irregularities that would limit the thickness or em-
placement of encapsulation material or reinforcement should be removed.
(Note 4). The shear displacement measuring system should
haveatravelofatleast100mmandanaccuracybetterthan0.1
7.1.2 Apply a layer of weak material at least 20 mm thick
mm. The normal and lateral displacement measuring systems
(for example, foamed polystyrene) around the base of the test
should have a travel of at least 20 mm and an accuracy better
block, and then encapsulate the remainder of the block in
than 0.05 mm. The measuring reference system (beams,
concreteorsimilarmaterialofsufficientstrengthandrigidityto
anchors, and clamps) should, when assembled, be sufficiently
prevent collapse or significant distortion during testing. Design
rigid to meet these requirements. Resetting of gages during the
the encapsulation formwork to ensure that the load bearing
test should be avoided, if possible.
faces are flat (tolerance 63 mm) and at the correct inclination
to the shear plane (tolerance 62°).
NOTE 4—The surface of encapsulating material is usually insufficiently
smooth and flat to provide adequate reference for displacement gages;
7.1.3 Carefully position and align reaction pads, anchors,
glass plates may be cemented to the specimen block for this purpose.
etc., if required to carry the thrust from normal and shear load
These plates should be of adequate size to accommodate movement of the
systems to adjacent sound rock.Allow all concrete time to gain
specimen. Alternatively, a temperature calibrated tensioned wire and
adequate strength prior to testing.
pulley system with gages remote from the specimen may be used. The
system, as a whole, must be reliable and must conform with specified
7.2 Consolidation of Test Specimen :
accuracy requirements. Particular care is needed in this respect when
employing electric transducers or automatic recording equipment.
7.2.1 Theconsolidationstageoftestingisnecessaryinorder
to allow pore water pressures, in the rock and especially in any
7. Procedure
filling material adjacent to the shear plane, to dissipate under
7.1 Preparation of Test Specimen :
full normal stress before shearing. Behavior of the specimen
7.1.1 Outline a test block such that the base of the block
during consolidation may also impose a limit on permissible
coincides with the plane to be sheared. The direction of
rate of shearing (see 7.3.3).
shearing should correspond, if possible, to the direction of
7.2.2 Check all displacement gages for rigidity, adequate
anticipated shearing in the full-scale structure to be analyzed
travel, and freedom of movement, and record a preliminary set
using the test results. To inhibit relaxation and swelling and to
of load and displacement readings.
prevent premature sliding, it is necessary to apply a normal
7.2.3 Raise normal load to the full value specified for the
test, recording any consequent normal displacements (consoli-
dation) of the test block as a function of time and applied loads
(Fig. 5 and Fig. 6).
7.2.4 Ifconsolidationoccurs,itmaybeconsideredcomplete
when the rate of change in normal displacement recorded at
each of the four gages is less than 0.005 mm/min for at least 10
min. Shear loading may then be applied.
7.3 Shear Testing:
7.3.1 The purpose of shearing is to establish values for the
peak and residual direct shear strengths of the test plane.
Corrections to the applied normal load may be required to hold
NOTE 1—Gages S1 and S2 are for shear displacement, L1 and L2 for
the normal stress constant (see 8.5). A shea
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.