Many coastal revetments employ geotextiles as filter-separators. In many instances, the harsh construction process would inevitably damage the geotextile, thus compromising its hydraulic performance. In order to serve effectively as a filter, the geotextile must survive the construction process without developing excessive punctures. Therefore, there is a need to accurately quantify the puncture resistance of geotextiles. To conduct a field drop test is one way to satisfy this need. A field drop-test employing a standard procedure was completed in Singapore. This procedure uses a standard impact block to deliver a constant magnitude of impact to the geotextile overlain by secondary armour stones. The assessment of damage of the geotextiles was based on statistical interpretation of a large number of drop-tests, taking into account the number and size of the punctures. Results of the field test were compared with standard index tests currently in use. It was found that existing index tests do not adequately reflect the puncture resistance of the geotextile. The results seem to suggest that the puncture resistance of the geotextile is more reliably indicated by the Energy Level of the geotextile. This paper presents the details of the standard drop test used in a field study.
Geotextiles are widely used in coastal revetments as separators and filters. As these structures are large and heavy consisting of layers of primary and secondary armour stones, the construction of such structures is tedious and time consuming. Rock dumping is a common construction method of many coastal revetments as it is an economical process. However, such a method would likely to damage the geotextile in the process, hence compromising its hydraulic performance (Lawson, 1992). In order to ensure that the geotextile is able to survive the construction process, the puncture resistance of the geotextile has to be accurately specified.