ISO 22477-6:2026

International
Standard
ISO 22477-6
First edition
Geotechnical investigation and
2026-03
testing — Testing of geotechnical
structures —
Part 6:
Load testing of soil nails and rock
bolts
Reconnaissance et essais géotechniques – Essais de structures
géotechniques —
Partie 6: Essai de chargement des clous et des boulons
Reference number
© ISO 2026
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 2
3.1 Terms, definitions .2
3.2 Symbols .3
4 Equipment . 3
4.1 Test set-up .3
4.2 Reaction system .4
4.3 Loading device .4
4.4 Load measurement .5
4.5 Displacement measurement .5
4.6 Time and temperature measurement .5
5 Test elements . 5
5.1 General .5
5.2 Sacrificial elements .6
5.3 Production elements .6
6 Execution of the test . 6
6.1 Time period between installation of test element and testing.6
6.2 Test preparation .6
6.3 Proof load .6
6.4 Datum load .7
6.5 Check of the de-bonded length .7
7 Test report . 7
7.1 General .7
7.2 Data report .7
7.3 Interpretative report .8
8 Test Method A . 8
8.1 General .8
8.2 Investigation test .8
8.2.1 Loading procedure .8
8.2.2 Measurement and checks .9
8.2.3 Interpretation of data .9
8.3 Suitability test .11
8.3.1 Loading procedure .11
8.3.2 Measurement and checks . 12
8.3.3 Interpretation of data . 12
8.4 Acceptance test . 13
8.4.1 Loading procedure . 13
8.4.2 Measurement and checks .14
8.4.3 Interpretation of data .14
9 Test Method B . 14
9.1 General .14
9.2 Loading procedure . 15
9.3 Measurement and checks .17
9.4 Interpretation of data .17
Annex A (informative) Creep rate α and critical creep load P .18
c
Bibliography . 19

iii
Foreword
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in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
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This document was prepared by Technical Committee ISO/TC 182, Geotechnics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 341, Geotechnical
Investigation and Testing, in accordance with the Agreement on technical cooperation between ISO and CEN
(Vienna Agreement).
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complete listing of these bodies can be found at www.iso.org/members.html.
A list of all parts in the ISO 22477 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
International Standard ISO 22477-6:2026(en)
Geotechnical investigation and testing — Testing of
geotechnical structures —
Part 6:
Load testing of soil nails and rock bolts
1 Scope
This document establishes the specifications for the execution of tension tests to be carried out on soil nails
and rock bolts.
NOTE 1 Soil nails and rock bolts are referred to as elements in the scope of this document.
NOTE 2 This document covers but is not limited to grouted soil nails and rock bolts.
NOTE 3 This document does not provide specification for the number of tests, the type of test, the Test Method, the
value of the proof load and the limiting criteria. These aspects reside in EN 1997-3 and its national annex or in similar
standards.
This document provides specifications for three types of tension tests: investigation tests, suitability tests
and acceptance tests.
Two methods of testing are recognised by this document. Test Method A involves step-loaded maintained
load tension tests. Test Method B involves constant displacement rate tension tests.
This document provides specifications for the experimental devices, the measurement apparatus, the test
procedures, the definition and the presentation of the test results and the content of records, aiming at:
a) measuring the pull-out resistance of a soil nail or a rock bolt;
NOTE 4 A loading test performed using this document provides the pulled-out resistance along the bonded
length, that will possibly differ from the pull-out resistance considered in design.
b) checking that a soil nail or rock bolt behaves as designed.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
EN 1990 (series), Eurocode: Basis of structural and geotechnical design
EN 1992-1-1, Eurocode 2: Design of concrete structures
EN 1993-5, Eurocode 3: Design of steel structures
EN 1997 (series), Eurocode 7: Geotechnical design

3 Terms, definitions and symbols
For the purposes of this document, the terms and definitions given in the EN 1990 series and the EN 1997
series and the following terms apply. ISO and IEC maintain terminology databases for use in standardization
at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Terms, definitions
3.1.1
applied load
P
tension load applied to the tendon head during the test
3.1.2
proof load
P
p
maximum load to which a test element is subjected in a particular load test
3.1.3
measured pull-out resistance
R
t,m
measured value of the pull-out resistance at the element-ground interface
3.1.4
tendon
soil nail or rock bolt reinforcing element
Note 1 to entry: Steel, fibreglass, etc.
3.1.5
test element
element on which a test is performed
3.1.6
sacrificial element
test element installed in the same way as production elements, but not forming part of the completed
reinforced ground structure
3.1.7
production element
test element which forms part of the completed reinforced ground structure
3.1.8
investigation test
load test to establish the geotechnical ultimate load resistance of a soil nail or rock bolt at the interface
between the element and the ground and to determine the behaviour of the element in the working load
range
3.1.9
suitability test
load test to confirm that a particular soil nail or rock bolt design will be adequate in particular ground
conditions
3.1.10
acceptance test
load test to confirm that an individual soil nail or rock bolt conforms with its acceptance criteria

3.2 Symbols
A minimum cross section of the tendon, including the connecting parts
t
E elastic modulus of the tendon material
t
L bonded length of the test element
b
L debonded length of the test element
db
L external length of the tendon
e
P applied load
P datum load
a
P critical creep load
c
P’ intermediate parameter to derive the critical creep load P
c c
P proof load
p
R measured pull-out resistance
t,m
f (= f ) tensile strength
tk uk
f yield strength at 0,2 % strain
t0,2k
s axial displacement of tendon head
s axial displacement of tendon head at time t , for creep rate determination
1 1
s axial displacement of tendon head at time t , for creep rate determination
2 2
t time
t minimum load step duration for Test Method A
min
t time at the beginning of the interval used for creep rate determination
t time at the end of the interval used for creep rate determination
α creep rate (defined in Annex A)
α limiting criterion for creep rate for Test Method A
A
4 Equipment
4.1 Test set-up
The equipment comprises (non-exhaustive list) of one jack, used as a loading device, displacement and load
monitoring devices, a reaction system, associated locking nuts, tendon extension.
An example of test set-up is given in Figure 1.
The test set-up shall take into account the aim of the test, the ground conditions and the expected
displacement of the test element.
Where the facing system or the load test reaction system can influence the test result, then the test element
should be de-bonded over the zone of influence.

Key
1 facing
2 reaction structure
3 extension of tendon
4 locking nut and plate at top of jack
5 displacement monitoring of tendon end
6 jack
7 pressure gauge
8 load cell
9 hydraulic system (pump)
10 tendon
11 grout
12 borehole
Figure 1 — Schematic layout of test loading system
4.2 Reaction system
The reaction system shall be designed to resist the proof load P , according to the relevant design standards.
p
The reaction system should be designed so as not to affect the measured pull-out resistance of the test
element, or to impose bearing pressures in excess of the bearing capacity of the facing.
It shall ensure that the applied load remains purely axial.
The reaction system may comprise the facing and additional rigid reaction elements (such as plates, beams,
etc.).
When no de-bonded length can be implemented, special attention should be taken to the choice of the
minimum distance between the test element and the reaction st
...