National foreword

This Published Document is the UK implementation of ISO/TR 18228‑5:2025.

The UK participation in its preparation was entrusted to Technical Committee B/553, Geosynthetics.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

This publication is not to be regarded as a British Standard.

Compliance with a Published Document cannot confer immunity from legal obligations.

This Published Document was published under the authority of the Standards Policy and Strategy Committee on 31 January 2025.

Foreword

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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 document 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).

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This document was prepared by Technical Committee ISO/TC 221, Geosynthetics.

A list of all parts in the ISO/TR 18228 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.

This corrected version of ISO/TR 18228‑5:2025 incorporates the following correction:

Formula (1) has been corrected.

Introduction

The ISO 18228 series provides guidance for designs using geosynthetics for soils and below ground structures in contact with natural soils, fills and asphalt. The series contains 10 parts which cover designs using geosynthetics, including guidance for characterization of the materials to be used and other factors affecting the design and performance of the systems which are particular to each part, with ISO/TR 18228‑1 providing general guidance relevant to the subsequent parts of the series.

The series is generally written in a limit state format and guidelines are provided in terms of partial material factors and load factors for various applications and design lives, where appropriate.

Ultimate limit state (ULS) design is necessary for some applications, e.g. slab foundation design, working platform design etc., but usually must be proven separately. This document is a state of practice report and information is provided in terms of the application of the mechanisms and design methods. A discussion on separation, filtration and other relevant engineering issues addressed with geosynthetics are addressed in the separate parts of ISO 18228.

This document includes information relating to the stabilization function. Details regarding design methodologies adopted in a number of regions are provided.

1 Scope

This document provides a summary of general guidance for the design of geosynthetics to fulfil the function of stabilization of granular layers in contact with natural soils, fills, asphalt or other materials.

The concepts of the summarised guidance are based on installed materials, the installation process and on either the strength or deformation behaviour, or both, of geosynthetics.

This document provides general considerations to support the design of unbound layers of paved and unpaved roads, working platforms and foundations utilizing the stabilization function of geosynthetics. This is typically for the serviceability limit state (SLS).

2 Normative references

3 Terms and definitions

4 Concepts and fundamental principles

4.1 General

4.2 Benefits

4.3 Confinement and particle restraint

4.4 Vehicular action

4.5 Loading conditions (cyclic and static)

4.6 Multi component systems

4.7 Static loads — Settlement control and limitation

4.8 Reduction in deformation from trafficking

4.9 Reduction in unbound aggregate degradation

4.10 Extension of design life

4.11 Ground and groundwater conditions

4.12 Climatic conditions

4.13 Sustainability

4.14 Impact of filtration, separation and drainage requirements

5 Typical applications

5.1 Stabilized granular (aggregate) layers in trafficked areas

5.2 Stabilized granular (aggregate) layers in railways

5.3 Stabilized granular (aggregate) layers in working platforms

6 Design methods

6.1 General

6.2 Unpaved roads

6.3 Paved roads

6.4 Working platforms and load transfer platforms

6.5 Railways

6.6 Design of the geosynthetics layout

7 Materials

7.1 Properties of aggregate

7.2 Key properties for geosynthetics – Internal confinement

7.3 Key properties for geosynthetics – External confinement

8 Testing

8.1 General

8.2 Accelerated pavement tests (APT)

8.3 Tests for geotextiles and geogrids

8.4 Tests for geocells

Bibliography