SIST EN ISO 22476-7:2013

Geotechnical investigation and testing - Field testing - Part 7: Borehole jack test (ISO 22476-7:2012)

This part of ISO 22476 specifies the equipment requirements, execution of and reporting on borehole jack tests. NOTE This part of ISO 22476 fulfils the requirements for borehole jack tests as part of geotechnical investigation and testing according to EN 1997-1 [1] and EN 1997-2 [2]. This part of ISO 22476 specifies the procedure for conducting a borehole jack test in ground stiff enough not to be adversely affected by the drilling operation. Two diametral cylindrical steel loading plates are placed in the ground and opened by pressure. Pressure applied to, and associated opening of the probe are measured and recorded so as to obtain a stress-displacement relationship of the ground for the range of the expected design stress. This part of ISO 22476 applies to test depths of ≤ 100 m and to testing either on land or off-shore.

Geotechnische Erkundung und Untersuchung - Felduntersuchungen - Teil 7: Seitendruckversuch (ISO 22476-7:2012)

Dieser Teil von ISO 22476 gilt für den Seitendruckversuch in Zusammenhang mit Felduntersuchungen als Teil der geotechnischen Erkundung und Untersuchung nach EN 1997-1 [1] und EN 1997-2 [2].
Dieser Teil von ISO 22476 legt das Verfahren zur Durchführung eines Seitendruckversuchs in einem Bau¬grund fest, der ausreichend steif ist, um durch den Bohrvorgang nicht beeinträchtigt zu werden. Zwei in den Baugrund eingebrachte zylindrische Druckplatten aus Stahl werden aufgespreizt. Der auf die Messsonde aufgebrachte Druck und deren dadurch bewirkte Ausdehnung werden gemessen und aufgezeichnet, um das Verhältnis zwischen Belastung und Aufweitung des Baugrunds im Bereich der erwarteten Bemessungs-belastungen zu ermitteln.
Dieser Teil von ISO 22476 gilt für Versuchstiefen von =< 100 m und für Versuche entweder auf Land oder auf See.

Reconnaissance et essais géotechniques - Essais en place - Partie 7: Essai au dilatomètre rigide diamétral (ISO 22476-7:2012)

L'ISO 22476-7:2012 traite des exigences relatives à l'appareillage, à l'exécution et au compte rendu des essais au dilatomètre rigide diamétral.
L'ISO 22476-7:2012 spécifie le mode opératoire permettant de réaliser un essai au dilatomètre rigide diamétral dans un terrain suffisamment ferme pour ne pas être affecté par l'opération de forage. Deux coquilles de chargement en acier cylindriques et diamétrales sont mises en place dans le terrain et déplacées par pression. La pression appliquée et le déplacement associé sont mesurés et enregistrés de manière à déterminer la relation contrainte-déplacement du terrain dans la plage des contraintes estimées dans le cadre de l'étude.
L'ISO 22476-7:2012 s'applique à des profondeurs d'essai inférieures ou égales à 100 m et aux essais en milieu terrestre ou aquatique.

Geotehnično preiskovanje in preskušanje - Preskušanje na terenu - 7. del: Preskus z bočnim tlakom v vrtini (ISO 22476-7:2012)

Ta del standarda ISO 22476 določa zahteve glede opreme, izvajanja preskusov z bočnim tlakom v vrtini ter poročanja v zvezi z njimi. OPOMBA Ta del standarda ISO 22476 izpolnjuje zahteve za preskuse z bočnim tlakom v vrtini v okviru geotehničnega preiskovanja in preskušanja v skladu s standardoma EN 1997-1 [1] in EN 1997-2 [2]. Ta del standarda ISO 22476 določa postopek za izvajanje preskusa z bočnim tlakom v vrtini v tleh, ki so dovolj trdna, da vrtanje nima negativnega vpliva. V tla se vstavita dve diametrični cilindrični jekleni nosilni plošči in razpreta z uporabo pritiska. Uporabljeni pritisk in povezano odprtje sonde se izmerita in zabeležita, da se pridobi odvisnost med napetostmi in deformacijami tal za razpon pričakovane projektne obremenitve. Ta del standarda ISO 22476 se uporablja za preskusne globine ≤ 100 m in preskušanje na kopnem ali na morju.

General Information

• Status: Published
• Public Enquiry End Date: 29-Sep-2012
• Publication Date: 21-May-2013
• ICS: 93.020 - Earthworks. Excavations. Foundation construction. Underground works
• Technical Committee: KON.007 - Geotechnics
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 13-Dec-2012
• Due Date: 17-Feb-2013
• Completion Date: 22-May-2013
• Ref Project: EN ISO 22476-7:2012 - Geotechnical investigation and testing - Field testing - Part 7: Borehole jack test (ISO 22476-7:2012)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 22476-7:2013
01-junij-2013
*HRWHKQLþQRSUHLVNRYDQMHLQSUHVNXãDQMH3UHVNXãDQMHQDWHUHQXGHO3UHVNXV
]ERþQLPWODNRPYYUWLQL,62
Geotechnical investigation and testing - Field testing - Part 7: Borehole jack test (ISO
22476-7:2012)
Geotechnische Erkundung und Untersuchung - Felduntersuchungen - Teil 7:
Seitendruckversuch (ISO 22476-7:2012)
Reconnaissance et essais géotechniques - Essais en place - Partie 7: Essai au
dilatomètre rigide diamétral (ISO 22476-7:2012)
Ta slovenski standard je istoveten z: EN ISO 22476-7:2012
ICS:
93.020 Zemeljska dela. Izkopavanja. Earthworks. Excavations.
Gradnja temeljev. Dela pod Foundation construction.
zemljo Underground works
SIST EN ISO 22476-7:2013 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 22476-7:2013

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SIST EN ISO 22476-7:2013


EUROPEAN STANDARD
EN ISO 22476-7

NORME EUROPÉENNE

EUROPÄISCHE NORM
December 2012
ICS 93.020
English Version
Geotechnical investigation and testing - Field testing - Part 7:
Borehole jack test (ISO 22476-7:2012)
Reconnaissance et essais géotechniques - Essais en place Geotechnische Erkundung und Untersuchung -
- Partie 7: Essai au dilatomètre rigide diamétral (ISO Felduntersuchungen - Teil 7: Seitendruckversuch (ISO
22476-7:2012) 22476-7:2012)
This European Standard was approved by CEN on 25 November 2012.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 22476-7:2012: E
worldwide for CEN national Members.

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SIST EN ISO 22476-7:2013
EN ISO 22476-7:2012 (E)
Contents Page
Foreword .3
2

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SIST EN ISO 22476-7:2013
EN ISO 22476-7:2012 (E)
Foreword
This document (EN ISO 22476-7:2012) has been prepared by Technical Committee CEN/TC 341
“Geotechnical Investigation and Testing", the secretariat of which is held by ELOT, in collaboration with
Technical Committee ISO/TC 182 "Geotechnics".
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by June 2013, and conflicting national standards shall be withdrawn at
the latest by June 2013.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
3

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SIST EN ISO 22476-7:2013

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SIST EN ISO 22476-7:2013
INTERNATIONAL ISO
STANDARD 22476-7
First edition
2012-12-01
Geotechnical investigation and testing —
Field testing —
Part 7:
Borehole jack test
Reconnaissance et essais géotechniques — Essais en place —
Partie 7: Essai au dilatomètre rigide diamétral
Reference number
ISO 22476-7:2012(E)
©
ISO 2012

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 1
3.2 Symbols and abbreviations . 3
4 Equipment . 4
5 Test procedure . 8
5.1 Calibration of the testing device . 8
5.2 Pocket drilling and device placing . 8
5.3 Loading programme . 8
5.4 Back-filling of borehole .10
5.5 Safety requirements .10
6 Test results .10
6.1 Basic equations .10
6.2 Loading tests . 11
6.3 Constant load test . 11
7 Reporting . 11
7.1 General . 11
7.2 Reporting of test results .12
7.3 Choice of axis scaling .13
7.4 Presentation of test results .13
Annex A (normative) Dimensions of borehole jacks and related device factors .14
Annex B (normative) Calibration and correction .15
Annex C (normative) Field report example .16
Annex D (informative) Test example .17
Annex E (normative) Placing the borehole jack in the ground .20
Annex F (normative) Resolutions and uncertainties .22
Bibliography .23
© ISO 2012 – All rights reserved iii

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 22476-7 was prepared by the European Committee for Standardization (CEN) Technical Committee
CEN/TC 341, Geotechnical investigation and testing, in collaboration with Technical Committee ISO/TC 182,
Geotechnics, Subcommittee SC 1, Geotechnical investigation and testing, in accordance with the Agreement
on technical cooperation between ISO and CEN (Vienna Agreement).
ISO 22476 consists of the following parts, under the general title Geotechnical investigation and testing —
Field testing:
— Part 1: Electrical cone and piezocone penetration test
— Part 2: Dynamic probing
— Part 3: Standard penetration test
— Part 4: Ménard pressuremeter test
— Part 5: Flexible dilatometer test
— Part 7: Borehole jack test
— Part 9: Field vane test
— Part 10: Weight sounding test [Technical Specification]
— Part 11: Flat dilatometer test [Technical Specification]
— Part 12: Mechanical cone penetration test (CPTM)
iv © ISO 2012 – All rights reserved

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
Introduction
The results of borehole jack tests are used for ground deformation calculations provided that the range of
stresses applied in the test are representative of the stresses caused by the proposed foundation. Local
experience normally improves the application of the results.
For identification and classification of the ground, the results of sampling (according to ISO 22475-1) from
each borehole are available for the evaluation of the tests. In addition, identification and classification results
(ISO 14688-1 and ISO 14689-1) are available from every separate ground layer within the desired investigation
depth (see EN 1997-2:2007, 2.4.1.4(2) P, 4.1(1) P and 4.2.3(2) P.)
© ISO 2012 – All rights reserved v

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SIST EN ISO 22476-7:2013

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SIST EN ISO 22476-7:2013
INTERNATIONAL STANDARD ISO 22476-7:2012(E)
Geotechnical investigation and testing — Field testing —
Part 7:
Borehole jack test
1 Scope
This part of ISO 22476 specifies the equipment requirements, execution of and reporting on borehole jack tests.
NOTE This part of ISO 22476 fulfils the requirements for borehole jack tests as part of geotechnical investigation and
testing according to EN 1997-1 [1] and EN 1997-2 [2].
This part of ISO 22476 specifies the procedure for conducting a borehole jack test in ground stiff enough not
to be adversely affected by the drilling operation. Two diametral cylindrical steel loading plates are placed in
the ground and opened by pressure. Pressure applied to, and associated opening of the probe are measured
and recorded so as to obtain a stress-displacement relationship of the ground for the range of the expected
design stress.
This part of ISO 22476 applies to test depths of ≤ 100 m and to testing either on land or off-shore.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including amendments) applies.
ISO 10012, Measurement management systems — Requirements for measurement processes and
measuring equipment
ISO 14688-1, Geotechnical investigation and testing — Identification and classification of soil —
Part 1: Identification and description
ISO 14689-1, Geotechnical investigation and testing — Identification and classification of rock — Part 1:
Identification and description
ISO 22475-1, Geotechnical investigation and testing — Sampling methods and groundwater measurements —
Part 1: Technical principles for execution
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
equipment for borehole jack test
borehole jack, hydraulic pump, measuring unit and cables to connect the borehole jack to the measuring unit
and the hydraulic pump
© ISO 2012 – All rights reserved 1

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
3.1.2
borehole jack sounding
series of successive operations necessary to perform borehole jack testing at a given location, i.e. forming a
borehole and performing borehole jack tests in this borehole
3.1.3
pocket for jack test
circular cylindrical cavity drilled in a borehole in which to insert the borehole jack device
3.1.4
borehole jack
circular cylindrical instrument in which two diametrically opposed curved plates on the outside are forced apart
by the application of hydraulic pressure to one or more small jacks located between them
3.1.5
borehole jack test
process of jacking two cylindrical loading plates diametrically outwards against the borehole wall and measuring
their associated expansion as a function of pressure and time
NOTE 1 See Figure 1.
NOTE 2 When testing in a borehole where the hydraulic head in the instrument supply line is likely to exceed the
hydraulic head of the fluid in the borehole, consideration must be given to restricting the expansion of the instrument before
it enters the pocket and at the conclusion of the test.
3.1.6
depth of test
distance between the ground level and the centre of the loading plates measured along the borehole axis
NOTE See Figure 2.
3.1.7
operator
qualified person who carries out the test
2 © ISO 2012 – All rights reserved

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
3.2 Symbols and abbreviations
For the purposes of this International Standard the symbols and abbreviations of Table 1 apply.
Table 1 — Symbols
Symbol Description Unit
2
A Projected area of the cylindrical loading plates on the plane normal to the axis of m
expansion
2
A Cross section area in one jack cylinder m
c
b
Width of the loading plates mm
d Design diameter of the jack mm
d Initial diameter of test pocket mm
0
d Current diameter of test pocket mm
c
d Diameter of the pocket at the start of the test mm
s
e
Associated loading plate expansion mm
e Loading plates expansion at time t or pressure p mm
1 1 1
e Loading plates expansion at time t or pressure p mm
2 2 2
Δe Loading plates expansion change equals diametral displacement of borehole mm
i
wall
E Modulus of borehole jack test for loading condition MPa
B
E Modulus of borehole jack test for unloading condition MPa
U
f Specific device factor –
k time-dependent strain parameter mm
f
l axial length of loading plates mm
l transducer centre-to-centre length mm
T
p applied pressure MPa
p calculated average contact stress MPa
c
p maximum contact stress MPa
max
p initial contact pressure MPa
s
p pressure at time t MPa
1 1
p pressure at time t MPa
2 2
q hydraulic pressure in a jack MPa
q maximum hydraulic pressure to be used MPa
max
q starting pressure of the test MPa
s
r friction resistance in one jack cylinder MPa
c
t time min
t time 1 of a constant stress test min
1
t time 2 of a constant stress test min
2
z
test depth m
z groundwater depth m
w
α tilt angle of the loading plates °
β opening angle of loading plates °
Δp change of calculated average contact stress MPa
c
ν
Poisson’s ratio –
© ISO 2012 – All rights reserved 3

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
4 Equipment
The principle of the borehole jack test is shown in Figure 1.
Key
1 ground surface
2 borehole
3 test pocket
4 loading plates
p applied pressure
A-A axial section
B-B cross section
Figure 1 — Example of a borehole jack test
The equipment to carry out borehole jack tests shall consist of the components shown in Figure 2.
4 © ISO 2012 – All rights reserved

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
Key
1 setting rods 8 borehole jack
2 signal cable 9 loading plate
3 measuring unit β opening angle
4 pressure gauge d initial diameter of test pocket
0
5 hydraulic pump b width of loading plate
6 pressure line z test depth
7 sediment collection tube B-B cross section
Figure 2 — Diagram of borehole jack equipment (depth less than 100 m)
The following components are obligatory:
— borehole jack (No. 8 in Figure 2);
— pressure line (No. 6 in Figure 2);
— signal cable (No. 2 in Figure 2);
— measuring unit (No. 3 in Figure 2);
— hydraulic pump (No. 5 in Figure 2);
— pressure gauge (No. 4 in Figure 2);
The following components are recommended:
— sediment collection tube to protect from caving (No. 7 in Figure 2);
© ISO 2012 – All rights reserved 5

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
— setting rods (No. 1 in Figure 2).
The nominal diameter of the borehole shall be some millimetres larger than the external diameter of the closed
borehole jack.
NOTE In the case of a borehole diameter of 101 mm, a borehole jack with an external diameter of 95 mm has been
shown to be suitable.
Annex A shows the geometrical parameters for various instruments.
The hydraulic pressure applied to the jacking cylinders between the loading plates shall be measured by an
electric transducer in the instrument (see Figure 3). The pressure may be recorded by a suitable measuring
device at the ground surface.
6 © ISO 2012 – All rights reserved

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
Key
1 displacement transducer d design diameter of the jack
l
2 hydraulic cylinders (variable No.) axial length of loading plates
3 spherical bearing surface l centre-to-centre distance of transducers
T
4 loading plate A-A axial section
5 axis of cylinder expansion B-B cross section
b width of the loading plate
Figure 3 — Sketch of expanded borehole jack: axial section and cross section
© ISO 2012 – All rights reserved 7

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
The expansion of the loading plates shall be monitored by one or more electric transducers. If the loading
plates are moved by hydraulic cylinders connected in parallel, at least two such transducers should be provided
so that any tilt of the loading plates is recorded. If the plates cannot tilt then a single transducer is sufficient.
The pressure line and the signal cable shall connect the downhole instrument to the measuring and control
units at the surface. The pressure line shall be connected to a hydraulic pump and a pressure gauge. The
signal cable shall connect the transducers in the instrument to the measuring unit.
5 Test procedure
5.1 Calibration of the testing device
Before testing, the equipment shall have been calibrated and applicable corrections determined (see Annex B).
Copies of the calibration documents shall be available at the job site. The following components of the equipment
shall be calibrated:
— displacement measuring system;
— pressure measuring system.
If any part of the system is repaired or exchanged, the calibration shall be verified.
5.2 Pocket drilling and device placing
A sample shall be recovered according to ISO 22475-1 at the test depth before the borehole jack test is carried out.
In unstable boreholes, a casing with a suitable diameter shall be placed down to a level 1,0 m above the desired test
location. A central hole or pocket of about 3 m in length shall then be cored at the nominal diameter for the instrument.
The pocket shall be drilled and the downhole instrument shall be placed in the test location with the minimum
of disturbance to the ground to be tested (see Annex E). Careful attention should be paid to the possible effects
of any sedimentation in the borehole.
The borehole jacking device shall be set into the pocket without delay. If necessary the instrument may be
orientated in the pocket by rotating the setting rods. The instrument shall enter the pocket so that the upper
edges of the jacking plates are at least 0,5 m from the pocket entry. The lower edges of the loading plates shall
not be closer than 0,5 m from the bottom of the pocket.
Borehole jack tests should not be carried out in ground where the stability of the borehole wall is not guaranteed.
5.3 Loading programme
5.3.1 General
The maximum hydraulic pressure, q , to be used shall be decided considering the maximum stress expected
max
to be applied to the ground by the proposed structure.
Two procedures may be chosen from to carry out the test:
— tests including load, unload and reload phases;
— tests in which time-dependent effects are important. These tests shall be individually designed according
to the exact data requirements.
In the first procedure, at least three unload/reload loops shall be carried out during the loading phase of
operation. The programme for these unload/reload loops shall be either given by the specifications for the test
or decided according to the observed progress of the test. The position of the first load reversal point has to be
decided by reference to the initial contact stress (see 6.1.1). Before commencing the descent phase of a reload
loop, enough time shall be allowed for time-dependent effects to become insignificant.
8 © ISO 2012 – All rights reserved

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
5.3.2 Loading phase
When starting the test, the loading plates shall be jacked slowly until they contact the wall of the test pocket.
This contact is indicated by an abrupt rise in the hydraulic pressure. This shall be the initial contact pressure, p .
s
Further pressure shall then be applied until it equals q , which shall be chosen between 2 % and 5 % of the
s
planned maximum pressure (see Figure 4).
Starting from this initial pressure, the soil or rock shall be loaded by stepped increments of pressure. The
duration of these pressure holds shall be chosen to be between 1 min and 3 min. Simultaneous readings of
pressure and loading plate expansion are recorded. Each loading phase shall be performed in five to eight
increments. Before the start of each unload in an unload/reload loop, the pressure shall be held constant until
time-dependent effects have declined to an acceptable value.
Deviations from the test procedure shall be reported in each individual case and their influence on the test
results shall be explained.
Key
a
First loading phase.
b
Second loading phase.
c
Third loading phase.
Figure 4 — Example of a loading test programme
5.3.3 Unloading phase
After having reached the maximum hydraulic pressure of the loading phase, the load shall be decreased in
steps with pressure and loading plate expansion being recorded.
The hydraulic pressure in an unloading phase shall never fall below q . The exact design of a reload loop shall
s
either be given by the specifications for the test or decided according to the observed progress of the test.
Sufficient data points shall be available in a reload loop to give a good definition of the whole loop.
5.3.4 End of loading
The loading phase shall be stopped when either:
— the maximum hydraulic pressure is reached; or
— the maximum admissible expansion of the loading plates is reached; or
— the tilt angle α of the loading plates is more than 3°. The tilt angle is defined as:
© ISO 2012 – All rights reserved 9

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
differencebetween transducers12and
tanα =
l
T
5.4 Back-filling of borehole
After completion of the tests, each borehole shall be back-filled and the site shall be restored according to the
specifications given in ISO 22475-1.
5.5 Safety requirements
National safety regulations shall be followed; e.g. for:
— personal health- and safety equipment;
— clean air if working in confined spaces;
— ensuring the safety of the equipment.
6 Test results
6.1 Basic equations
6.1.1 Calculation of average contact stress
The average contact stress, p , between the loading plates and the borehole wall shall be determined by
c
F
p = (1)
c
A
where
A is one loading plate projected area;
F is the force exerted by the jacks on one loading plate:
Fn=−Aq r (2)
()
cc
where
n is the number of cylinders;
q is the hydraulic pressure;
A is the cross-section area of one cylinder of the jack;
c
r is a friction-effect correction which must be determined by a calibration (see B.4).
c
6.1.2 Modulus of borehole jack test, E
B
The modulus of the jack test, E , shall be determined by the general formula
B
d
c
Ef=⋅ ⋅ Δp (3)
B i
Δe
i
where
f is the specific device factor dependent on the opening angle of the loading plates β and on
Poisson’s ratio ν;
10 © ISO 2012 – All rights reserved

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SIST EN ISO 22476-7:2013
ISO 22476-7:2012(E)
NOTE Device specific factors f for instruments in use are given in Annex A.
d is the current diameter of the pocket;
c
Δe is the loading plates expansion change due to Δp ;
i i
Δp is the change of calculated average contact stress;
i
E is always specific to the stress range considered.
B
6.2 Loading tests
The test data shall be plotted as shown in Figure D.1. The loading plate expansion, e, is plotted as a function of
the calculated average contact stress, p . The loading modulus of jack test, E , shall be determined from the
c B
test data Δe and Δp according to Formula (3).
c
When evaluating borehole jack tests, Δp shall only be selected within a range of any one loading or unloading
c
phase. Whichever phase is selected determines whether the modulus measure
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