ISO/TS 20432:2022
(Main)Guidelines for the determination of the long-term strength of geosynthetics for soil reinforcement
Guidelines for the determination of the long-term strength of geosynthetics for soil reinforcement
This document provides guidelines for the determination of the long-term strength of geosynthetics for soil reinforcement. This document describes a method of deriving reduction factors for geosynthetic soil-reinforcement materials to account for creep and creep rupture, installation damage and weathering, and chemical and biological degradation. It is intended to provide a link between the test data and the codes for construction with reinforced soil. The geosynthetics covered in this document include those whose primary purpose is reinforcement, such as geogrids, woven geotextiles and strips, where the reinforcing component is made from polyester (polyethylene terephthalate), polypropylene, high density polyethylene, polyvinyl alcohol, aramids and polyamides 6 and 6,6. This document does not cover the strength of joints or welds between geosynthetics, nor whether these might be more or less durable than the basic material. Nor does it apply to geomembranes, for example, in landfills. It does not cover the effects of dynamic loading. It does not consider any change in mechanical properties due to soil temperatures below 0 °C, nor the effect of frozen soil. The document does not cover uncertainty in the design of the reinforced soil structure, nor the human or economic consequences of failure.
Lignes directrices pour la détermination de la résistance à long terme des géosynthétiques pour le renforcement du sol
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Standards Content (Sample)
TECHNICAL ISO/TS
SPECIFICATION 20432
First edition
2022-12
Guidelines for the determination
of the long-term strength of
geosynthetics for soil reinforcement
Lignes directrices pour la détermination de la résistance à long terme
des géosynthétiques pour le renforcement du sol
Reference number
© ISO 2022
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ii
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, abbreviated terms and symbols . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 2
3.3 Symbols . 3
4 Design procedure . 4
4.1 General . 4
4.2 Design lifetime . 4
4.3 Causes of degradation . 5
4.4 Design temperature . 5
5 Determination of long-term creep strain . 5
5.1 General . 5
5.2 Extrapolation . 6
5.3 Time-temperature superposition methods . 6
5.4 Isochronous curves . 7
5.5 Weathering, chemical and biological effects . 7
6 Determination of long-term strength . 8
6.1 Tensile strength . 8
6.2 Reduction factors . 8
6.3 Modes of degradation . 8
7 Creep rupture . 9
7.1 General . 9
7.2 Measurement of creep rupture: conventional method . 10
7.3 Curve fitting (conventional method) . 11
7.4 Curve fitting for time-temperature block shifting of rupture curves .13
7.5 Strain shifting and the stepped isothermal method . 14
7.6 Extrapolation and definition of reduction factor or lifetime . 15
7.7 Residual strength . 16
7.8 Reporting of results . 16
7.9 Procedure in the absence of sufficient data . 16
8 Installation damage . .17
8.1 General . 17
8.2 Data recommended . 17
8.3 Calculation of reduction factor . 18
8.4 Procedure in the absence of direct data . 18
8.4.1 General . 18
8.4.2 Interpolation from measurements with different soils. 18
8.4.3 Interpolation between products of the same product line . 19
8.4.4 Laboratory damage tests . 19
9 Weathering, chemical and biological degradation .19
9.1 General . 19
9.2 Data recommended for assessment . 20
9.3 Weathering . 20
9.4 Chemical degradation . 21
9.4.1 Causes of chemical degradation. 21
9.4.2 Evidence from service experience . 21
9.4.3 Accelerated chemical degradation tests .22
9.4.4 Oxidation of polyolefins . 26
9.4.5 Hydrolysis of polyesters . 27
iii
9.4.6 Procedure in the absence of sufficient data .29
9.5 Biological degradation .29
10 Determination of long-term strength .29
10.1 Factor of safety f .29
s
10.2 Design for residual strength .30
11 Reporting .30
Bibliography .31
iv
Foreword
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different types of ISO documents should be noted. This document was drafted in accordance with the
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This document was prepared by Technical Committee ISO/TC 221, Geosynthetics.
This first edition of ISO/TS 20432 cancels and replaces ISO/TR 20432:2007, which has been technically
revised. It also incorporates the Technical Corrigendum ISO/TR 20432:2007/Cor 1:2008.
The main changes are as follows:
— Subclause 7.4 has been modified to further detail and clarify the fitting of linear regression curves
to time-temperature block shifted creep-rupture test results.
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.
v
TECHNICAL SPECIFICATION ISO/TS 20432:2022(E)
Guidelines for the determination of the long-term strength
of geosynthetics for soil reinforcement
...
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