Linking Design With Specification Of Geotextiles

Geotextiles usually make up a fraction of the cost of an engineered structure and are primarily incorporated in the stabilisation or strengthening measures in the foundation or base of the structure. As such, the design of these geotextile used in any structure is critical to the long term life of the structure. While geotextile design methodology is reasonably well understood the correct specification of the geotextile is often overlooked or poorly understood and implemented. A poorly constructed specification will often result in installation of a geotextile which bears little or no resemblance to the geotextile which was originally designed. This often leads to poor performance and associated high maintenance of the structure and at worst failure.

Many of the geotextile test methods have been adapted from the general textile industry and can not be directly related to the engineering functions that geotextiles are designed to perform. Different test methods throughout this document are described as either an Index test or a Performance test. Index test results are obtained quickly, with good reproducibility, which permits the comparison of one product to another and are ideally suited to the manufacturing quality assurance process. Performance tests allow direct assessment of the likely in-situ interaction between the soil and a geotextile.

Therefore, understanding the intricacies of the test methods and how they relate to the application of the geotextile is the key to the project. This document will attempt to improve the understanding of the relevant test methods and their application.

Understanding the test method alone is not sufficient to ensure the correct product is supplied. The designer must understand how the information presented in manufacturer’s data sheets is compiled and how this relates to the product supplied to site. It is critical that designers can interpret individual test results obtained as either Manufacturing Quality Assurance (MQA) or Construction Quality Assurance (CQA) as failure to correctly interpret results can lead to incorrect acceptance or rejection of products supplied.

In an attempt to cover all the issues raised above the following topics will be discussed in some detail

•  Relating function to test method
•  Test methods overview
•  Data sheet interpretation
•  Conclusion