SIST EN ISO 18674-3:2018

SLOVENSKI STANDARD
01-marec-2018
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Geotechnical investigation and testing - Geotechnical monitoring by field instrumentation
- Part 3: Measurement of displacements across a line: Inclinometers (ISO 18674-3:2017)
Geotechnische Erkundung und Untersuchung - Geotechnische Messungen - Teil 3:
Verschiebungsmessungen senkrecht zu einer Linie mit Inklinometern (ISO 18674-
3:2017)
Reconnaissance et essais géotechniques - Surveillance géotechnique par
instrumentation in situ - Partie 3: Mesurages des déplacements perpendiculairement à
une ligne par inclinomètre (ISO 18674-3:2017)
Ta slovenski standard je istoveten z: EN ISO 18674-3:2017
ICS:
17.020 Meroslovje in merjenje na Metrology and measurement
splošno in general
93.020 Zemeljska dela. Izkopavanja. Earthworks. Excavations.
Gradnja temeljev. Dela pod Foundation construction.
zemljo Underground works
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 18674-3
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2017
EUROPÄISCHE NORM
ICS 13.080.20; 93.020
English Version
Geotechnical investigation and testing - Geotechnical
monitoring by field instrumentation - Part 3: Measurement
of displacements across a line: Inclinometers (ISO 18674-
3:2017)
Reconnaissance et essais géotechniques - Surveillance Geotechnische Erkundung und Untersuchung -
géotechnique par instrumentation in situ - Partie 3: Geotechnische Messungen - Teil 3:
Mesurages des déplacements perpendiculairement à Verschiebungsmessungen senkrecht zu einer Linie mit
une ligne par inclinomètre (ISO 18674-3:2017) Inklinometern (ISO 18674-3:2017)
This European Standard was approved by CEN on 3 September 2017.

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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18674-3:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 18674-3:2017) has been prepared by Technical Committee ISO/TC 182
"Geotechnics" in collaboration with Technical Committee CEN/TC 341 “Geotechnical Investigation and
Testing” the secretariat of which is held by BSI.
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 2018, and conflicting national standards shall be
withdrawn at the latest by June 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations 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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 18674-3:2017 has been approved by CEN as EN ISO 18674-3:2017 without any
modification.
INTERNATIONAL ISO
STANDARD 18674-3
First edition
2017-10
Geotechnical investigation and
testing — Geotechnical monitoring by
field instrumentation —
Part 3:
Measurement of displacements across
a line: Inclinometers
Reconnaissance et essais géotechniques — Surveillance géotechnique
par instrumentation in situ —
Partie 3: Mesurages des déplacements perpendiculairement à une
ligne par inclinomètre
Reference number
ISO 18674-3:2017(E)
©
ISO 2017
ISO 18674-3:2017(E)
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved

ISO 18674-3:2017(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 3
5 Instruments . 4
5.1 General . 4
5.2 Probe inclinometers . 5
5.3 In-place inclinometers . 6
5.4 Inclinometer casing. 8
5.5 Measuring range, accuracy and repeatability . 9
6 Installation and measuring procedure . 9
6.1 General . 9
6.2 Installation of guide tubes at accessible surfaces and in concrete . 9
6.3 Installation of guide tubes in boreholes .10
6.3.1 Drilling of boreholes .10
6.3.2 Installation of guide tubes .10
6.3.3 Securing borehole measuring locations .12
6.4 Installation of in-place inclinometers .12
6.5 Carrying out the measurement .13
6.5.1 Instrumentation check and calibration .13
6.5.2 Measurement .13
7 Data processing and evaluation .14
8 Reporting .15
8.1 Installation report .15
8.2 Monitoring report .15
Annex A (normative) Measuring and evaluation procedure .16
Annex B (normative) Deflectometers .20
Annex C (informative) Backfill materials.24
Annex D (informative) Geo-engineering applications .26
Annex E (informative) Measuring examples .27
Bibliography .38
ISO 18674-3:2017(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 182, Geotechnics.
A list of all parts in the ISO 18674 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved

INTERNATIONAL STANDARD ISO 18674-3:2017(E)
Geotechnical investigation and testing — Geotechnical
monitoring by field instrumentation —
Part 3:
Measurement of displacements across a line:
Inclinometers
1 Scope
This document specifies the measurement of displacements across a line by means of inclinometers
carried out for geotechnical monitoring. General rules of performance monitoring of the ground, of
structures interacting with the ground, of geotechnical fills and of geotechnical works are presented in
ISO 18674-1.
This document also refers to deflectometers (see Annex B) to supplement inclinometers for the
determination of horizontal displacements across horizontal measuring lines.
NOTE In general, there are two independent displacement components acting across measuring lines.
Inclinometers allow the determination of the two components for vertical measuring lines. For horizontal lines,
inclinometers are limited to the determination of the vertical component only.
If applied in conjunction with ISO 18674-2, this document allows the determination of displacements
acting in any direction.
This document is applicable to:
— checking geotechnical designs in connection with the Observational Design procedure;
— monitoring of geotechnical structures prior to, during and after construction (e.g. natural slopes,
slope cuts, embankments, excavation walls, foundations, dams, refuse dumps, tunnels);
— deriving geotechnical key parameters (e.g. from results of pile load tests or trial tunnelling);
— identification and monitoring of active shear planes in the ground.
NOTE This document fulfils the requirements for the performance monitoring of the ground, of structures
interacting with the ground and of geotechnical works by the means of inclinometers as part of the geotechnical
investigation and testing in accordance with References [1] and [2].
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 18674-1:2015, Geotechnical investigation and testing — Geotechnical monitoring by field
instrumentation — Part 1: General rules
ISO 18674-2:2016, Geotechnical investigation and testing — Geotechnical monitoring by field
instrumentation — Part 2: Measurement of displacements along a line: Extensometers
ISO 22475-1:2006, Geotechnical investigation and testing — Sampling methods and groundwater
measurements — Part 1: Technical principles for execution
ISO 18674-3:2017(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18674-1 and ISO 18674-2 and
the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
inclinometer
system for monitoring displacements across a measuring line by means of inclination measurements in
the field
Note 1 to entry: The system essentially consists of an instrument with one or more tilt sensors (3.2), a guide tube,
a means to measure the position of the instrument in the guide tube and a read-out device.
Note 2 to entry: Data from inclinometers require evaluation, which can be done using proprietary software or
spreadsheets.
3.2
tilt sensor
gravity-activated electric sensor for inclination measurements
3.3
probe inclinometer
system comprising a probe with one or more built-in tilt sensors (3.2) for step-by-step measurements of
the inclination on a measuring line
Note 1 to entry: Also known as a traversing inclinometer.
Note 2 to entry: Vertical probe inclinometers measure displacements in horizontal directions.
Note 3 to entry: Horizontal probe inclinometers measure displacements in vertical directions (settlements
or heave).
Note 4 to entry: An alternative to horizontal probe inclinometers is a hydrostatic probe system.
Note 5 to entry: See also Reference [3].
3.4
in-place inclinometer
IPI
inclinometer system comprising a single element, or a series of elements, with one or more built-in tilt
sensors (3.2) in each element, for measurement of the inclination at specific locations on a measuring
line without removing the instrument
Note 1 to entry: In-place inclinometers exist which can measure at all inclinations, but when in near-horizontal
position, deflections from the azimuth cannot be measured.
3.5
uniaxial inclinometer
system for inclination measurements in a single plane
Note 1 to entry: Common for horizontal measuring lines.
3.6
biaxial inclinometer
system for inclination measurements in two planes 90° to each other
Note 1 to entry: Common for vertical measuring lines.
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ISO 18674-3:2017(E)
3.7
inclinometer casing
guide tube appropriate to the inclinometer system being used
Note 1 to entry: Commonly, the inner side of inclinometer casings have four longitudinal keyways. Commercially
available casings differ with regard to material, dimension, type of coupling, number of keyways etc. (see 5.4).
Note 2 to entry: The corners of casings with square section can be considered as keyways.
3.8
gauge length
L
distance between adjacent contact points of the instrument
Note 1 to entry: For probe inclinometers (3.3), L is commonly 0,5 m or 1,0 m.
3.9
base length
distance between adjacent measuring points used in the evaluation procedure
Note 1 to entry: For probe inclinometers (3.3), the base length is equal to the gauge length (3.8).
4 Symbols
Symbol Name Unit
A measuring plane of the probe which coincides with the plane of the guide wheels —
a lateral displacement component in Plane A m
B measuring plane of the inclinometer probe normal to Plane A —
b lateral displacement component in Plane B m
d depth, distance m
F subscript for follow-up measurement —
h height with respect to sea level m
i number of a measuring point —
L gauge length of an inclinometer or deflectometer probe m
l distance between measuring points m
n total number of measuring points along a measuring line —
R subscript for reference measurement —
t elapsed time s
t date and time of a follow-up measurement —
F
t date and time of a reference measurement —
R
u, v, w displacement component in x-, y- and z-direction, respectively m
x, y, z local coordinates of a guiding tube or borehole m
α tilt angle of the probe axis in Plane A ° (degree)
β tilt angle of the probe axis in Plane B ° (degree)
ψ angle between guide tube coordinate x and plane A of the inclinometer ° (degree)
θ, ρ auxiliary quantities ° (degree)
ISO 18674-3:2017(E)
5 Instruments
5.1 General
5.1.1 Probe and in-place inclinometers should be distinguished from each other (see Table 1 and
Figures 1, 2 and A.1).
Table 1 — Inclinometer types
Automatic data
No. Type Sub-type Principal measuring procedure
acquisition
Probe moved inside a guide tube from one
Inclinometer
Probe (see measuring point to the next (see Figures 1
1 — Vertical inclinometer Not common
5.2) and A.1). Repeated measurements within
— Horizontal inclinometer
the measuring period.
In-place inclinometer (IPI)
Instrument inserted into a guide tube and
In-place — Vertical inclinometer
2 held in measuring position throughout the Common
(see 5.3) — Horizontal inclinometer
measuring period
— Combined
NOTE A combined IPI is a series of elements in which some elements act as vertical and some act as horizontal
inclinometers.
5.1.2 Changes of tilt shall be measured by comparison of the measured values with those of the
reference measurement. Displacements of the measuring points across the measuring line shall be
deduced in accordance with Annex A.
5.1.3 The point to which the measurements are related shall be denoted the “reference point”.
5.1.4 For absolute displacement measurements, the coordinates of the reference point shall be
independently determined or assumed as fixed and verified.
NOTE If the reference point is assumed to be at the deepest measuring point, surveying of the inclinometer
head can serve as a check.
5.1.5 The sensing element shall consist of a housing with either one (uniaxial configuration) or two
(biaxial configuration) built-in tilt sensors. In the case of a biaxial configuration, the tilt sensors shall be
installed with axes perpendicular (90°) to each other.
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ISO 18674-3:2017(E)
5.1.6 The installation planes of the tilt sensors shall be denoted as the instrument Planes A and B,
whereby Plane A shall coincide with the plane of the guide wheel assemblies (see 5.2.5). The planes shall
+
be durably marked onto the inclinometer housing, e.g. by the mark “A ” showing the positive A direction.
Key
1 undeformed inclinometer casing I top view of inclinometer casing
2 deformed inclinometer casing II side view
3 inclination measuring element III detail of inclinometer element in R- and F- positions
+
4 area of the ground subject to displacements A A direction
+
5 undeformed deeper ground for base fixity B B direction
6 reference point (here, the axis of the bottom wheel L gauge length
is set at the lowest measuring position)
7 depth measuring device R initial position of inclinometer casing at the reference
measurement
Δα change of inclination F position of inclinometer casing at a value change
measurement
Figure 1 — Measuring concept for inclinometers (schematic)
5.2 Probe inclinometers
5.2.1 Inclinometer probes shall be moved incrementally along the measuring line, whereby each
increment shall not exceed the gauge length L of the probe.
5.2.2 The depth measuring device shall have permanent and wear-resistant depth measuring marks.
The spacing of the marks should be equal to the gauge length L of the probe.
5.2.3 The length of the depth measuring device and the spacing between the marks shall be checked
throughout the measuring project. Changes shall be recorded.
ISO 18674-3:2017(E)
NOTE 1 Monitoring displacements by probe inclinometers requires good repeatability of the probe’s
positioning at the respective measuring points (see 6.5.2.3 and 7.4).
NOTE 2 The use of a cable gate or a suspension pulley can help to ensure good positioning.
5.2.4 Inclinometer casing shall be used as guide tubes (see 5.4).
5.2.5 The inclinometer probe shall be equipped with two spring-loaded guide wheel assemblies. The
width of the guide wheels shall fit the keyways of the inclinometer casings. The force of the springs
should ensure a central positioning of the probe in the casing, even for extended monitoring periods with
repeated measuring runs.
5.3 In-place inclinometers
5.3.1 The principal setup of in-place inclinometers should be as in Figure 2.
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ISO 18674-3:2017(E)
a) IPI with wheel assembly b) IPI with wheel assembly c) IPI without wheel assembly
and continuous string of and discontinuous string of and discontinuous string of
sensors sensors sensors
Key
1 top suspension 7 gauge length, L
2 wheel assembly 8 base length
3 universal joint 9 intermediate suspension
4 guide tube 10 expanding joint or skid
5 connecting element 11 embedment material
6 sensor
Figure 2 — Principal setup and components of in-place inclinometers (IPIs)
5.3.2 It shall be ensured that the lengths of the connecting elements remain constant throughout the
measuring project (no elongation, no shrinkage).
5.3.3 For a continuous string of measuring elements [see Figure 2 a)], the flexibility of the measuring
elements shall be negligible.
NOTE This requirement applies in particular to horizontal strings (see Reference [4]).
ISO 18674-3:2017(E)
5.3.4 For a discontinuous string of measuring elements [see Figure 2 b) and c)], engineering judgement
shall be used to integrate angular changes into displacements.
5.3.5 Gauge lengths should not exceed 2 m. Within an installation, they can be varied to adjust to local
conditions.
NOTE Shorter lengths will commonly lead to better results.
5.3.6 The long-term reliability of the sensor signals should be considered. Intermittent removal of
the instrument for re-calibration should be avoided and is only permissible if especially justified and
documented.
NOTE An approach to checking the long-term reliability is to make measurements in two adjacent guide tubes;
one for the IPI and one for a probe inclinometer (“diversification”; in accordance with ISO 18674-1:2015, 5.4).
5.4 Inclinometer casing
5.4.1 The section of the casing shall be selected against the background of the specific measurement
requirements and the expected ground movements across the measuring line (see also 6.3.1.1).
5.4.2 The material of the casing shall fulfil the following requirements:
— be neutral to groundwater and other soil components;
— be durable during complete measuring period;
— be robust for installation;
— be flexible for bending.
NOTE 1 Acrylonitrile butadiene styrene (ABS) is a common inclinometer casing material.
NOTE 2 Metal casings, especially aluminium casings, can corrode, for example, by short-circuiting between
ground layers with different electric potentials or by aggressive groundwater.
5.4.3 If the inclinometer casing has internal keyways, the spiralling of the keyways shall be less than
0,25°/m. The string of casings should be assembled so that the keyways are continued over the joints.
5.4.4 When selecting the casing, the flexibility of the assembled string, including the backfill material
(see 6.3.2.5 and Annex C), should be considered with respect to the site conditions.
5.4.5 If using telescopic couplings, the design of the couplings, their telescopic travel and the method
of fixing should be such as to allow the string of casings to readily compress or extend in the direction of
the measuring line by an amount equal to the ground compression or extension.
NOTE 1 Telescopic couplings can have major detrimental effects on the accuracy of measurements and on the
tracking and depth positioning control of the probe.
NOTE 2 The addition of external corrugated sleeving to flush-coupled casing can eliminate damage caused
by ground settlement. However, there is no need to extend the sleeving into the undeformed deeper ground (see
Figure 1).
5.4.6 Prior to installation, the casings should be stored in a safe and secure place, laid horizontally and
supported to avoid deformations due to self weight. They should also be protected from direct sunlight.
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ISO 18674-3:2017(E)
5.5 Measuring range, accuracy and repeatability
5.5.1 Table 2 provides some order of magnitude information regarding accuracy and repeatability of
inclinometers. Inclinometer measurements shall be in accordance with Table 2.
Table 2 — Requirements of inclinometer measurements
Inclinometer
Type Line Issue
Vertical Horizontal
±0,02 % full scale
1 Accuracy of the instrument (probe or IPI element) (e.g. ±0,1 mm/m
for ±30° range)
Repeatability (precision) of a complete survey along a measuring line:
Probe
Difference between the cumulated displacements of a measuring
2 ±2 mm ±10 mm
point relative to a reference point 30 m apart, when repeatedly
carrying out the survey under repeatability conditions (see 5.5.2)
Repeatability (precision) of a string of IPI elements, measuring
range ±10°, spaced at 2 m:
In-place 3 ±2 mm ±2 mm
Difference between the cumulated displacements of a measuring
point relative to a reference point 30 m apart, when repeatedly
carrying out the survey under repeatability conditions (see 5.5.2)
Stability of sensor signal:
Probe and
4 ±0,1 mm/m
in-place
Difference after a 24 h period under repeatability conditions
5.5.2 The repeatability of a measuring value (see Lines No. 2 and 3 in Table 2) should be established
within the reference measurement (see 6.5.2.5).
NOTE 1 Repeatability conditions comprise, i.e.
— identical observer;
— identical measurement procedure;
— identical instruments;
— identical influencing quantities.
NOTE 2 The values are specified for measurements in the A-axis. The B-axis measurements are commonly
less accurate. Achieving the specified values for the secondary axis (B-axis) requires dedicated measurements
with the wheels in the corresponding keyways.
6 Installation and measuring procedure
6.1 General
Particular attention should be paid to the selection of suitable guide tubes and their installation as they
are critical for the quality of the measurements.
6.2 Installation of guide tubes at accessible surfaces and in concrete
6.2.1 When installing guide tubes at the surface of above-ground engineered structures, attention
should be paid to a durable fixation. An exposure of the tubes to environmental impacts such as direct
sunlight should be avoided, e.g. by protective covers.
6.2.2 When installing guide tubes in reinforced concrete, the tubes can be either placed inside a void
former that is pre-installed before the concreting or fixed directly to the reinforcement. If the guide tubes
ISO 18674-3:2017(E)
are placed prior to concreting, care should be taken to avoid damage by mechanical effects or by curing
temperatures.
6.2.3 When using a void former, the annulus between the guide tube and the void former shall be
completely filled with a suitable material. The backfill material shall be documented.
NOTE Void formers are commonly used for depths greater than 20 m or if the concrete structure is more
than 1 m thick.
6.2.4 On sheet piles, the installation of the guide tube can be done prior to piling with protection or,
after piling, inside a void former. A pre-installed square steel tube can also be used as a guide tube.
6.3 Installation of guide tubes in boreholes
6.3.1 Drilling of boreholes
6.3.1.1 The diameter of the borehole shall be selected based on the intended measuring system and the
ground conditions. An oversized annulus between the borehole and wall guide tube should be avoided.
NOTE 1 The bigger the borehole and the guide tube diameters, the lower the risk of an early blockage of the
guide tube by ground displacements across the borehole axis.
NOTE 2 Small diameter boreholes and guide tubes, e.g. those with guide tube diameter of 48 mm, are
generally considered inappropriate in soils and rocks; however, not necessarily in cases in which displacements
are expected to be very small and distributed over broad zones, such as in concrete.
NOTE 3 The larger the annulus between guide tube and borehole wall, the more likely the risk that small
lateral displacements are disguised in the inclinometer measurements. See Reference [5].
6.3.1.2 The borehole and its guide tube (see 6.3.2) should extend into that part of the ground or
structure which is expected to remain stable throughout the monitoring project. The extension should be
at least six times the gauge length, L, i.e. at least 3 m for a 0,5 m probe and 6 m for a 1,0 m probe.
NOTE 6.3.1.2 aims to establish a base fixity which assists in the evaluation of the inclinometer measuring
data and serves to detect and quantify systematic errors (see 7.4).
6.3.1.3 The drilling procedure should be specified individually for each measuring location. Drilling
shall be carried out and documented in accordance with ISO 22475-1. For vertical installations the
inclination of the borehole should be kept within ±2° of vertical, at any point along the borehole.
NOTE Drilling with core recovery provides direct information on the ground conditions and enables a better
interpretation of the measuring results.
6.3.1.4 Prior to the installation of the guide tube, the borehole shall be carefully cleaned, for example,
by flushing with water or compressed air.
6.3.2 Installation of guide tubes
6.3.2.1 The inclinometer casing should be installed with one keyway in the reference direction. In
vertical boreholes, the reference direction should be the direction of the anticipated principal movement.
In horizontal and inclined boreholes, the reference direction should be the “top” of the borehole (in
accordance with ISO 18674-1:2015, Figure B.1). The keyway which is in the reference direction shall be
the reference keyway and shall be durably marked, for example, by cutting a notch at the top of the guide
tube into that keyway or by identifying it by a water-resistant and wear-resistant mark.
6.3.2.2 Installation procedures shall minimize twisting of the string of inclinometer casing. No attempt
shall be made to re-orientate the reference keyway after the guide tube has been assembled and installed.
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ISO 18674-3:2017(E)
NOTE The measurement of the deviation between the keyway and reference direction which might become
apparent after the installation is commonly carried out geodetically or by means of a compass.
6.3.2.3 For guide tubes greater than 50 m in length, the twist of the keyways along the casing shall be
checked by independent measurements.
NOTE 1 Measurement of casing twist is commonly carried out by means of spiral or compass probes.
NOTE 2 To enhance the quality of the measurements, it is good practice to carry out twist measurements for
casing lengths greater than 20 m.
6.3.2.4 After inserting the guide tube, any drill casing shall be removed. Care shall be taken not to
rotate the guide tube in the borehole when lifting the drill casing.
NOTE It can be necessary to remove the drill casing in stages while backfilling (see 6.3.2.5) below the
drill casing.
6.3.2.5 The annulus between the guide tube and borehole wall shall be completely backfilled to ensure
conformity between the movement of the ground and the measurement. The composition of the backfill
material shall be documented and its properties considered in relation to the surrounding medium.
NOTE 1 One of the purposes of backfilling is to re-establish separations between different aquifers in
accordance with ISO 22475-1:2006, 5.5.4.
NOTE 2 Common backfill materials are low-strength cement-based mortar and cement-bentonite suspensions.
Granular backfill material can be used in specific circumstances (see Annex C).
NOTE 3 Possible quality control and preventative measures:
— comparing the geometric volume of the annulus and that of the backfilled material;
— in fractured ground and soils with a high permeability, insertion of a geotextile hose to retain the grout.
NOTE 4 When installing the backfill, it is good practice to use a tremie pipe and to grout under pressure from
the bottom of the borehole up, in order to ensure complete backfilling of the annulus. For boreholes deeper than
35 m, it is good practice to use multiple tremie pipes at multiple heights along the tube.
6.3.2.6 In order to prevent snaking of the guide tube due to buoyancy forces, buoyancy of the guide
tubes shall be compensated by filling the tubes with clean water, by ballasting the base and/or anchoring
the base of the guide tube string. No attempt shall be made to push the top of the casing after insertion.
It shall be ensured that no backfill material, dirt, soil or rock particles, etc. get inside the guide tube, for
example, by the use of a top cap.
NOTE 1 Any snaking of the guide tubes seriously reduces the accuracy of the inclinometer measurements.
NOTE 2 Support of the guide tube base can be achieved by lowering a steel pipe inside the tube down to the
bottom cap (reinforced to ensure that it does not become damaged while lowering the steel pipe), by use of a
casing anchor and/or by initial backfilling of the bottom parts of the annulus between the guide tube and the
borehole (i.e. backfilling in stages).
6.3.2.7 When selecting and installing the guide tube, it shall be ensured that the following are achieved:
a) Prevent collapse of the guide tube under the pressure of back fill suspensions.
NOTE 1 Possible preventative measures:
— provide internal support by filling the guide tube with water;
— use appropriate material or wall thickness for the guide tubes;
— sequential backfilling in lifts of limited height (e.g. <30 m).
ISO 18674-3:2017(E)
b) Sufficient sealing of the couplings, including the end caps (top and bottom), in order to prevent any
ingress of backfill material into the guide tube which can render the entire guide tube useless.
NOTE 2 Possible preventative measures:
— multiple and clean taping of the coupling joints and gluing of the coupling connections;
— selection of guide tubes with an integral O-ring seal between the casing segments.
6.3.3 Securing borehole measuring locations
The head of a guide tube shall be protected by a cap to prevent material falling into the tube. If vandalism
is of concern, the cap should be lockable (see Figure 3).
Key
1 top cap, lockable
2 cap of inclinometer casing
3 inclinometer casing
4 lock
5 protective sleeve
6 concrete bed
7 backfill
8 borehole
Figure 3 — Example of a lockable inclinometer head
6.4 Installation of in-place inclinometers
6.4.1 Interference between the IPI connecting elements and the guide tube shall be avoided at
installation and over the full range of expected displacements.
NOTE At the installation, the initial profile of the guide tube is determined by a probe inclinometer and used
to choose appropriate connecting elements (e.g. length, diameters, measuring range).
12 © ISO 2017 – All rights reserved

ISO 18674-3:2017(E)
6.4.2 When the in-place inclinometer elements have been installed into the guide tube, it shall be
ensured that the string of elements is in tension or compression (depending on the model of instrument)
in accordance with the manufacturer’s instructions.
For near horizontal measuring lines, setting rods may be required for positioning the in-place
inclinometer elements inside the guide tube.
For near vertical measuring lines where the uppermost in-place inclinometer element does not coincide
with the top of the guide tube, a suspension cable will be required to correctly position the string of in-
place inclinometer elements.
6.4.3 When the in-place inclinometer elements have been positioned in the guide tube, they shall be
fixed in that position and the position shall be documented.
NOTE Fixation can be achieved by firmly attaching the cable or the setting rods to the collar of the guide tube.
6.5 Carrying out the measurement
6.5.1 Instrumentation check and calibration
6.5.1.1 For general function checks and calibrations, see ISO 18674-1:2015, 5.6.
6.5.1.2 Inclinometer probes shall be regularly re-calibrated. If not otherwise specified by the
manufacturer, the maximum interval shall be two years. If the instrument was not in use for more than two
years, re-calibration shall be carried out immediately prior to the measuring survey. Re-calibrations are
also necessary after repair or the exchange of any mechanical or electrical components (including cable).
6.5.2 Measurement
6.5.2.1 The measurements shall be carried out according to Annex A and in conjunction with the
requirements of ISO 18674-1:2015, Clause 7.
6.5.2.2 For probe inclinometers, the guide tube shall be surveyed by the probe using a step-by-step
procedure. The stability of the readings is critical for a correct measurement. Therefore, at the beginning
of a survey, the probe shall be brought to the point furthest from the collar of the guide tube and left
there to adjust to the ambient temperature until the readings are considered to be sufficiently stable.
The probe shall then be moved sequentially to each respective measuring point in the direction of collar
of the guide tube. On reaching the collar of the guide tube, the probe is removed from the guide tube,
reversed (i.e. rotated by 180°,), returned to the measuring point that is furthest from the collar of the
guide tube and the sequence is repeated in the reversed position to complete the inclinometer survey of
the guide tube.
NOTE 1 The time of the probe to adjust to the ambient temperature varies and depends on site and probe
conditions.
NOTE 2 The purpose of the reversal of inclinometer probes between the two runs of a complete measuring
survey is to eliminate zero point deviation within the system. For vertical inclinometers, the reversal is turning
the probe through 180° around its longitudinal axis (the cable entry is unchanged), while for horizontal
inclinometers the reversal is turning the probe through 180° in
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