EN ISO 12958-2:2020

• Abstract:

  This document specifies a method for determining the constant-head water flow capacity within the plane of a geotextile or geotextile-related product, using boundary materials and test conditions of interest. A standard series of test conditions are proposed, involving soil confinement, low hydraulic gradients, seating times and an array of normal loads.

• Status: Published
• Publication Date: 03-Nov-2020
• Withdrawal Date: 30-May-2021
• ICS: 59.080.70 - Geotextiles
• Technical Committee: CEN/TC 189 - Geotextiles and geotextile-related products
• Drafting Committee: CEN/TC 189/WG 4 - Hydraulic testing
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 04-Nov-2020
• Completion Date: 04-Nov-2020
• Directive: Harmonized Standard305/2011 - Regulation (eu) No 305/2011 of the European Parliament and of the Council of 9 march 2011 laying down harmonised conditions for the marketing of construction products and repealing council directive 89/106/eec
• Mandate: M/107 - Mandate to CEN/CENELEC concerning the execution of standardization work for harmonized standards on geotextiles
• Ref Project: SIST EN ISO 12958-2:2021 - Geotextiles and geotextile-related products - Determination of water flow capacity in their plane - Part 2: Performance test (ISO 12958-2:2020)

• Replaces: EN ISO 12958:2010 - Geotextiles and geotextile-related products - Determination of water flow capacity in their plane (ISO 12958:2010)
• Effective Date: 08-Jun-2022
• Refers: ISO 9862:2005 - Geosynthetics — Sampling and preparation of test specimens
• Effective Date: 25-Aug-2026
• Refers: ISO 5813:1983 - Water quality — Determination of dissolved oxygen — Iodometric method
• Effective Date: 25-Aug-2026
• Refers: ISO 2854:1976 - Statistical interpretation of data — Techniques of estimation and tests relating to means and variances
• Effective Date: 25-Aug-2026
• Refers: ISO 9863-1:2016 - Geosynthetics — Determination of thickness at specified pressures — Part 1: Single layers
• Effective Date: 25-Aug-2026
• Refers: ISO 10318-1:2015 - Geosynthetics — Part 1: Terms and definitions
• Effective Date: 09-Feb-2026
• Refers: EN 437:2018 - Test gases - Test pressures - Appliance categories
• Effective Date: 28-Jan-2026
• Refers: EN 14762:2006 - Wood flooring - Sampling procedures for evaluation of conformity
• Effective Date: 28-Jan-2026
• Refers: EN 1744-1:2009/FprA1 - Tests for chemical properties of aggregates - Part 1: Chemical analysis
• Effective Date: 28-Jan-2026
• Refers: EN ISO 4892-2:1999 - Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon-arc sources (ISO 4892-2:1994)
• Effective Date: 28-Jan-2026
• Referred By: EN 13252:2014+A1:2015 - Geotextiles and geotextile-related products - Characteristics required for use in drainage systems
• Effective Date: 28-Jan-2026
• Referred By: EN 13252:2000 - Geotextiles and geotextile-related products - Characteristics required for use in drainage systems
• Effective Date: 28-Jan-2026
• Referred By: EN 13252:2014 - Geotextiles and geotextile-related products - Characteristics required for use in drainage systems
• Effective Date: 28-Jan-2026
• Referred By: EN 13252:2016 - Geotextiles and geotextile-related products - Characteristics required for use in drainage systems
• Effective Date: 28-Jan-2026
• Consolidated By: ISO 12958-2:2020 - Geotextiles and geotextile-related products — Determination of water flow capacity in their plane — Part 2: Performance test
• Effective Date: 12-Feb-2026

Overview

EN ISO 12958-2:2020 (ISO 12958-2:2020) defines a laboratory performance test for measuring the constant‑head in‑plane water flow capacity of geotextiles and geotextile‑related products. The standard specifies test apparatus, specimen preparation, boundary materials and a series of standard test conditions that reflect realistic project situations - including soil confinement, low hydraulic gradients, varied normal loads and seating times - so that transmissivity (flow per unit width) can be determined under service‑relevant conditions.

Key topics and requirements

• Scope: Determines constant‑head, in‑plane flow capacity using boundary materials and conditions of interest; proposes a set of standard test conditions.
• Test principle: Measures volumetric flow rate per unit width under a defined normal compressive stress (σ), hydraulic gradient (i), seating time (t) and boundary conditions (b).
• Specimen handling and selection: Requirements for number, dimensions and conditioning of specimens; guidance on granular boundary materials and soil confinement.
• Apparatus & procedure: Details on test equipment, seating and loading procedures, low‑gradient constant‑head setup, and measurement practice.
• Calculations & reporting: Methods to express performance in‑plane water flow capacity (q_perf), correction factors (e.g., temperature conversion), and required test report content.
• Special considerations:
  • Geotextile intrusion into drainage cores and its effect on transmissivity.
  • Directional testing for products with discrete draining elements (flow may be direction‑dependent).
  • Limitations regarding long‑term creep, chemical/biological clogging and durability - these require additional standards or assessment.

Applications and practical value

• Provides a realistic laboratory method to evaluate in‑plane transmissivity of drainage geotextiles and geocomposites under project‑specific conditions.
• Useful for:
  • Product development and quality control by manufacturers.
  • Specification and acceptance testing by owners, consultants and test laboratories.
  • Design verification where soil confinement, low hydraulic gradients and service loading influence drainage performance (e.g., landfills, retaining structures, pavements, subsurface drainage systems).
• Helps assess the impact of soil‑geotextile interaction and seating/creep on short‑ to mid‑term in‑plane flow capacity.

Who should use this standard

• Geotechnical and civil engineers, geosynthetic manufacturers, independent testing laboratories, specification writers and researchers involved in drainage design and performance assessment of geotextiles and geocomposites.

Related standards

• ISO 12958-1 (other part of the series)
• ISO 18325 (prefabricated vertical drains)
• ISO 9862 (sampling and specimen preparation)
• ISO 9863-1 (thickness at specified pressures)
• ISO 10318-1 (terms and definitions)
• ISO/TR 18228-4 (information on hydraulic gradient significance)

Keywords: geotextiles, in‑plane water flow capacity, transmissivity, EN ISO 12958-2:2020, geotextile performance test, hydraulic gradient, soil confinement, seating time.

SLOVENSKI STANDARD
01-januar-2021
Nadomešča:
SIST EN ISO 12958:2012
Geotekstilije in geotekstilijam sorodni izdelki - Ugotavljanje zmogljivosti pretoka
vode v ravnini - 2. del: Preskus lastnosti (ISO 12958-2:2020)
Geotextiles and geotextile-related products - Determination of water flow capacity in their
plane - Part 2: Performance test (ISO 12958-2:2020)
Geotextilien und geotextilverwandte Produkte - Bestimmung des
Wasserableitvermögens in der Ebene - Teil 2: Leistungs-Prüfverfahren (ISO 12958-
2:2020)
Géotextiles et produits apparentés - Détermination de la capacité de débit dans leur plan
- Partie 2: Test de performance (ISO 12958-2:2020)
Ta slovenski standard je istoveten z: EN ISO 12958-2:2020
ICS:
59.080.70 Geotekstilije Geotextiles
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 12958-2
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2020
EUROPÄISCHE NORM
ICS 59.080.70 Supersedes EN ISO 12958:2010
English Version
Geotextiles and geotextile-related products -
Determination of water flow capacity in their plane - Part
2: Performance test (ISO 12958-2:2020)
Géotextiles et produits apparentés - Détermination de Geotextilien und geotextilverwandte Produkte -
la capacité de débit dans leur plan - Partie 2: Essai de Bestimmung des Wasserableitvermögens in der Ebene
performance (ISO 12958-2:2020) - Teil 2: Leistungs-Prüfverfahren (ISO 12958-2:2020)
This European Standard was approved by CEN on 12 October 2020.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, 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
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12958-2:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 12958-2:2020) has been prepared by Technical Committee ISO/TC 221
"Geosynthetics" in collaboration with Technical Committee CEN/TC 189 “Geosynthetics” the secretariat
of which is held by NBN.
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 May 2021, and conflicting national standards shall be
withdrawn at the latest by May 2021.
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.
This document supersedes EN ISO 12958:2010.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 12958-2:2020 has been approved by CEN as EN ISO 12958-2:2020 without any
modification.
INTERNATIONAL ISO
STANDARD 12958-2
First edition
2020-10
Geotextiles and geotextile-related
products — Determination of water
flow capacity in their plane —
Part 2:
Performance test
Géotextiles et produits apparentés — Détermination de la capacité de
débit dans leur plan —
Partie 2: Essai de performance
Reference number
ISO 12958-2:2020(E)
©
ISO 2020
ISO 12958-2:2020(E)
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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 the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

ISO 12958-2:2020(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus and materials. 2
6 Specimens and boundary conditions . 4
6.1 Handling. 4
6.2 Selection. 4
6.3 Number and dimensions . 5
6.3.1 Geotextile or geotextile-related product . 5
6.3.2 Other geosynthetic products . 5
6.4 Granular materials used as boundaries . 5
6.5 Specimen condition . 6
7 Test procedure . 6
8 Calculations and expression of results . 8
8.1 Products with a continuous structure (i.e. with no discrete draining elements) . 8
8.2 Products with discrete draining elements . 8
8.3 Graphical representation . 9
9 Test report .10
Annex A (informative) Determination of the correction factor R for conversionto a water
T
temperature of 20 °C .12
Annex B (informative) Experimental data and calculations for a specimen .14
Annex C (informative) Use of a reference soil as a boundary condition .15
Bibliography .16
ISO 12958-2:2020(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 of 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
www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 221, Geosynthetics, in collaboration with
the European Committee for Standardization (CEN) Technical Committee CEN/TC 189, Geosynthetics,
in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This first edition of ISO 12958-2, together with ISO 12958-1, cancels and replaces ISO 12958:2010,
which has been technically revised.
A list of all parts in the ISO 12958 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 © ISO 2020 – All rights reserved

ISO 12958-2:2020(E)
Introduction
The results obtained under this test procedure do not compare with those obtained under ISO 12958-1,
even if some of the test conditions are similar.
Many geosynthetic products can creep under constant load, i.e. see their thickness diminish over
time, which can influence their in-plane water flow capacity. Although a seating time typically greater
than the one used in ISO 12958-1 is used, this test does not cover all creep-related issues for drainage
geocomposites. Assessment of long-term flow capacity involves further considerations.
This procedure can be useful to assess the effect of geotextile intrusion into the drainage core on the
transmissivity of a drainage product, using soil from a particular project as a stress-distribution layer
in contact with the geotextile.
Other test methods can be more suitable for the characterization of particular drainage products, such
as ISO 18325 for prefabricated vertical drains. It is the responsibility of the user to assess the limit
of this test procedure and select the appropriate test method, test conditions or both that adequately
reflect the particular needs for their project.
In this test method, the flow capacity of the product in a given direction is evaluated considering soil
confinement, service load and service hydraulic gradient, as well as primary creep. However:
— For some products and designs, ensuring the product performance may require controlling the flow
capacity of the product in both directions, for example for products with discrete draining elements,
where the flow capacity significantly depends on the direction of flow. For these situations, the test
shall be performed in both directions.
— Other field-related issues affect material long-term performance, such as secondary or tertiary creep,
chemical or biological clogging, chemical resistance and durability, installation and backfilling.
These issues are covered in separate standards and it is essential that they be considered while
designing with geosynthetics.
INTERNATIONAL STANDARD ISO 12958-2:2020(E)
Geotextiles and geotextile-related products —
Determination of water flow capacity in their plane —
Part 2:
Performance test
1 Scope
This document specifies a method for determining the constant-head water flow capacity within the
plane of a geotextile or geotextile-related product, using boundary materials and test conditions of
interest. A standard series of test conditions are proposed, involving soil confinement, low hydraulic
gradients, seating times and an array of normal loads.
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 2854, Statistical interpretation of data — Techniques of estimation and tests relating to means and
variances
ISO 5813, Water quality — Determination of dissolved oxygen — Iodometric method
ISO 9862, Geosynthetics — Sampling and preparation of test specimens
ISO 9863-1, Geosynthetics — Determination of thickness at specified pressures — Part 1: Single layers
ISO 10318-1, Geosynthetics — Part 1: Terms and definitions
3 Terms and definitions
For the purposes of this document, terms and definitions in ISO 10318-1 and the following terms and
definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
normal compressive stress
σ
compressive stress normal to the plane of the geotextile or geotextile-related product, expressed in
kilopascals [kPa]
3.2
in-plane flow
Q
fluid flow within the geotextile or geotextile-related product and parallel to its plane, expressed in
litres per second [l/s]
ISO 12958-2:2020(E)
3.3
performance in-plane water flow capacity
q
p perf (σ,i,t,b)
volumetric flow rate of water per unit width of specimen at a defined normal compressive stress (σ),
hydraulic gradient (i), seating time (t) and boundary conditions (b), expressed in litres per second per
meter [(l/s)/m]
3.4
hydraulic gradient
i
ratio of the head loss in the geotextile or geotextile-related product specimen to the distance between
two measuring points within the geotextile or geotextile-related product
1)
Note 1 to entry: ISO/TR 18228-4 provides information on the significance of the hydraulic gradient.
3.5
seating time
period of time during which the product is maintained under constant compressive stress before a
measurement is made, expressed in hours (h)
3.6
boundary conditions
b
type of materials contacting the specimen on its external faces
Note 1 to entry: Materials may be soil or granular materials, concrete or rigid platen, or any material likely to be
in contact with the geotextile or geotextile-related product.
3.7
geotextile intrusion
effect of the external loads pushing the geotextile into the draining core of the geocomposite, reducing
the flow area, on a geocomposite where a geotextile is combined with a draining core
4 Principle
The flow of water within the plane of a geotextile or geotextile-related product is measured under
normal compressive stresses, seating time, hydraulic gradients and boundary conditions (contact
surfaces) which are representative of a particular field condition.
5 Apparatus and materials
5.1 Constant-head in-plane water flow apparatus, as follows:
a) The apparatus shall be capable of maintaining a constant head loss at different water levels, at least
those corresponding to the selected hydraulic gradients, while maintaining a water head at the
point of discharge not greater than 100 mm.
b) Reading of the water in open-tube piezometers or manometers is acceptable for hydraulic gradients
of 0,1 or more (that is, applied head loss of 30 mm or more). For hydraulic gradients smaller than
0,1 (head loss of 30 mm or less), the use of water pressure transducers is necessary to achieve a
maximum permissible measurement error of 5 % of the measured head loss. The water pressure
transducers shall be located to capture the actual length of flow over which the water head is
measured (effective flow length on Figure 1).
c) If the average water head above the specimen exceeds 100 mm, and the applied normal load is equal
to or less than 20 kPa, the normal stress shall be corrected considering the average water head.
1) Under preparation. Stage at the time of publication: ISO/CD TR 18228-4:2020.
2 © ISO 2020 – All rights reserved

ISO 12958-2:2020(E)
d) The apparatus shall include a loading mechanism capable of exerting a constant normal compressive
stress on the geotextile or geotextile-related specimen to a maximum permissible measurement
error of 1 % of the applied load or 1 kPa, whichever is greater, for a period of time exceeding the
seating time.
e) The apparatus should have a minimum width of 0,2 m and a minimum net hydraulic length of
0,3 m. It shall be capable of testing specimens up to a thickness of 50 mm. It shall also be capable of
accepting boundary materials to the thickness needed for the test.
For a specimen length of 0,3 m, the use of test cells narrower than 0,3 m may affect the properties
measured on products exhibiting a highly oriented structure, such as biplanar geonets.
The height of the cell shall be sufficient to accommodate installation of a thick layer of soil as per
the requirements of 6.4.
f) Soils and other permeable materials used in the test setup to reproduce the boundaries conditions
shall be confined in a membrane. The membrane shall not limit soil intrusion into the drain.
Membranes with a thickness not exceeding 0,7 mm and a tensile elastic modulus not exceeding
1,12 kN/m were found satisfactory. The membrane shall be checked before each test for integrity. It
shall not present any deformation nor puncture visible with the naked eye.
g) Leakage through the apparatus shall not exceed 5 % of the flow rate measured during the test. To
verify the leak rate of the apparatus, a blank test shall be conducted periodically using a closed-
cell foam in place of the geosynthetic, as well as sand wrapped in a plastic film above and below
the closed-cell foam, and tested under the minimum and the maximum normal load which can be
applied with the apparatus, as well as the average of these normal loads. The leak check shall be
performed using the highest hydraulic gradient which can be applied.
An exampl
...