EN ISO 11276:2014

SLOVENSKI STANDARD
01-maj-2014
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Soil quality - Determination of pore water pressure - Tensiometer method (ISO
11276:1995)
Bodenbeschaffenheit - Bestimmung des Porenwasserdrucks - Tensiometerverfahren
(ISO 11276:1995)
Qualité du sol - Détermination de la pression d'eau dans les pores - Méthode du
tensiomètre (ISO 11276:1995)
Ta slovenski standard je istoveten z: EN ISO 11276:2014
ICS:
13.080.20 Fizikalne lastnosti tal Physical properties of soils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 11276
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2014
ICS 13.080.20
English Version
Soil quality - Determination of pore water pressure - Tensiometer
method (ISO 11276:1995)
Qualité du sol - Détermination de la pression d'eau dans les Bodenbeschaffenheit - Bestimmung des
pores - Méthode du tensiomètre (ISO 11276:1995) Porenwasserdrucks - Tensiometerverfahren (ISO
11276:1995)
This European Standard was approved by CEN on 13 March 2014.

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

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11276:2014 E
worldwide for CEN national Members.

Contents Page
Foreword .3
Foreword
The text of ISO 11276:1995 has been prepared by Technical Committee ISO/TC 190 “Soil quality” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 11276:2014 by
Technical Committee CEN/TC 345 “Characterization of soils” the secretariat of which is held by NEN.
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 September 2014, and conflicting national standards shall be
withdrawn at the latest by September 2014.
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 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 11276:1995 has been approved by CEN as EN ISO 11276:2014 without any modification.
INTERNATIONAL
ISO
STANDARD
First edition
1995-09-01
Seil quality - Determination of pore water
pressure - Tensiometer method
Quake du sol - Determination de Ia Pression d’eau dans les pores -
M6 thode du tensiomk tre
Reference number
ISO 11276: 1995(E)
ISO 11276:1995(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. Esch 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.
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.
International Standard ISO 11276 was prepared by Technical Committee
lSO/TC 190, Seil quality, Subcommittee SC 5, Physical methods.
Annex A forms an integral part of this International Standard. Annexes B,
C, D, E and F are for information only.
0 ISO 1995
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronie or mechanical, including photocopying and
microfilm, without Permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-l 211 Geneve 20 l Switzerland
Printed in Switzerland
ii
INTERNATIONAL STANDARD 0 ISO ISO 11276:1995(E)
Soil quality - Determination of pore water
pressure - Tensiometer method
NOTES
1 Scope
2 Pore water pressure is also referred to as tensiometer
This International Standard specifies methods for the
pressure.
determination of pore water pressure in both unsatu-
rated and saturated soil using tensiometers. The 3 The pore water pressure represents the sum of the
pressures due to interfacial forces acting between the
methods are applicable for in situ pore water pressure
water, air and solid phases of the soil (matric pressure), the
measurements in the field, as well as for monitoring
part of the mass of overlying material not carried by the soil
pore water pressure in, for example, plant Containers
Skeleton and therefore carried by the soil water (overburden
or soil cores used in experimental procedures.
pressure; this pressure is often considered as part of the
matric pressure) and the local air pressure within the soil
At normal atmospheric pressures, i.e. about 100 kPa,
(pneumatic pressure). Under most circumstances, the
the application of these methods is limited to a range
overburden and pneumatic pressures are Zero.
of pressures down to about - 85 kPa. The range is
lower atmospheric pressures.
reduced at
Tensiometers will not function if sub-zero tempera-
2.2 matric pressure: The amount of work that must
tures occur at the measurement depth. Their accuracy
be done in Order to transport reversibly and
is influenced by seil and air temperature fluctuations.
isothermally an infinitesimal quantity of water, ident-
Tensiometer response time ranges from a few sec-
ical in composition to the soil water, from a pool at the
onds to several days. To obtain reliable measure-
elevation and the external gas pressure of the Point
ments under field conditions, tensiometers require
under consideration, to the soil water at the Point
frequent servicing.
under consideration, divided by the volume of water
transported.
A tensiometer provides Point measurements of pore
water pressure. To measure pore water pressure at
several tensiometers will be 2.3 pneumatic pressure: The amount of work that
different depths,
must be done in Order to transport reversibly and
necessary. In the field, replicate sets of instruments
isothermally an infinitesimal quantity of water, ident-
will be required if the spatial variability of the soil is to
be allowed for. ical in composition to the soil water, from a pool at
atmospheric pressure and at the elevation of the Point
under consideration, to a similar pool at an extemal
gas pressure of the Point under consideration, divided
by the volume of water transported.
2 Definitions
NOTE 4 Soil water pressure tan be considered as a
For the purposes of this International Standard, the
pressure equivalent of soil water potential. The same ap-
plies to the soil water head, the head equivalent of soil
following definitions apply.
water potential.
NOTE 1 Additional definitions are given in E.2, for infor-
mation only. The relationship between these is
‘P-p, = p - h-g-p,
2.1 pore water pressure: The sum of matric and
pneumatic pressures. where
0 ISO
ISO 11276:1995(El)
Y is the soil water potential, in joules per kilogram
4 Apparatus
on a mass basis;
4.1 Tensiometer, usually consisting of a porous
is the pressure equivalent of soil water poten-
P
CUP, a connecting tube and/or a body tube, a pressure
tial, in joules per cubic metre on a volume basis
(1 J/m3 = 1 N/m2 = 1 Pa);
Sensor and a mechanism for expelling any air which
accumulates within the tensiometer. The details of
h is the head equivalent of soil water potential, in
the design depend primarily on whether the instru-
joules per newton on a forte basis
ment is intended for field or indoor use and the type
(1 J/N=l m);
of pressure Sensor employed; examples are shown in
is the density of water, in kilograms per cubic
figure 1. Annex B provides information on materials
Pw
metre;
for the construction of tensiometers and on their
construction.
is the acceleration due to gravity, in metres per
S
second squared.
4.1.1 Porous CUP, made of a porous material of air-
In this International Standard pressure equivalents and soil
entry value (i.e. the pressure required to forte air
water Potentials are used. The corresponding unit of
through the water-saturated CUP) larger in magnitude
measurement is the Pascal (Pa). Table 1 provides conver-
than the lowest pore water pressure to be measured
sions between soil water potential and its pressure and
and the known hydraulic conductivity. The material
head equivalents.
shall be rigid and not subject to degradation in soil.
Usually unglazed ceramic is used; alternatives are de-
scribed in annex B.
3 Principle
4.1.2 Connecting and body tubes, made from ap-
A tensiometer comprises a porous cup that is per-
propriate materials of low permeability to water and
meable to water connected to a pressure-measuring
gas and connected by leakproof joints. Rigid or semi-
device. The pores of the wall of the cup are small
rigid tubing shall be used to connect the tensiometer
enough to prevent air passing through when it is wet.
to the pressure Sensor (see annex B). The function
The porous cup is filled with water. When the cup is
of the connecting tube may, in part or totally, be
placed in the soil, water within the tensiometer flows
served by the body tube.
through the porous wall to the soil, or soil water flows
into the tensiometer, until the pressure of the water The body tube usually fills the hole remaining above
on both sides of the porous wall is equal. When or behind the tensiometer cup after inserting it into
equilibrium has been reached, the measured pressure the soil. lt is a rigid tube with the same outside di-
of the water inside the tensiometer, after correction ameter as the porous CUP. In many designs, it is filled
with water, but in others it forms a casing for smaller
for the differente in height between the pressure
tubes connected to the porous cup and/or cables at-
Sensor and the porous cup equals the pore water
tached to a pressure transducer located behind the
pressure of the soil water at the Position of the
CUP.
porous CUP.
Table 1 - Conversions between soil water potential and its pressure and head equivalents
Pressure equivalent Head equivalent
Potential
Parameter to be converted
Pa m
Jh
1 0,102 0 x 1o-3
Pressure equivalent (Pa) 1 o-3
Head equivalent (m) 9 807 1
9,807
Potential (J/kg) IO3 0,102 0
NOTES
potential, multiply by the factor
1 To convert from the potential or its equivalent in the first vertical to another equivalent or
given, for example:
a potential of 1 J/kg has a pressure equivalent of IO3 Pa and a head equivalent of 0,102 0 m.
2 Acceleration due to gravity = 9,807 m/s2
Density of water = 1 000 kg/m3
0 ISO
ISO 11276:1995(E)
4.1.3 Pressure Sensors. Several forms are used in If a tensiometer assembly of new design or of untried
tensiometers, the most common being mercury materials is to be used, it shall be tested for leaks
manometers, Bourdon gauges and electrical pressure under pressure and/or under vacuum before instal-
transducers. The use of other types of manometer is lation. This procedure is recommended for all instal-
lations.
permissible. The accuracy of the pressure Sensor de-
termines how accurately the pressure of the water
within the tensiometer tan be measured.
5 Procedure
Annex A details the construction and use of mercury
5.1 Installation of tensiometers
manometers for use with tensiometers. The other
pressure Sensors are described in annex C.
Tensiometers may be installed vertically or horizon-
tally, whichever is most suitable for the required pur-
The accuracy of Bourdon gauge and pressure
pose. Install each tensiometer so that the centre of
transducer tensiometers shall be verified before in-
the porous cup is at the depth at which measurement
stallation and at least annually thereafter.
is
...