Evaluating the puncture survivability of geotextiles in construction of coastal revetments

Abstract

Geotextiles are widely used in coastal revetment work as a separator and a filter between the base soil and the armor stones. In order for them to function properly as hydraulic filters in coastal revetments, they must first be able to survive the construction process. The tensile strength and mass of geotextiles are often specified to meet the survivability requirements. But these parameters do not necessarily reflect the puncture resistance characteristics of the geotextiles. Hence, there is a need to understand the performance of these geotextiles in meeting the survivability requirements and to quantify the puncture resistance of geotextiles more confidently. An extensive field drop-test was recently completed in Singapore to study the puncture resistance of geotextiles. This field test comprised 784 controlled drop-tests using a standardized drop block released from heights ranging from 0.5m to 2.5m. Five different geotextiles (two woven and three non-woven) were tested, including three new double layer geotextiles. The drop tests were conducted for geotextiles laid over different soil conditions, with varying thickness of secondary armor stones. Both horizontal and sloping grounds were used. The extent of damage on the geotextiles was assessed based on statistical interpretation of a large number of drop-tests, taking into account the number and size of the punctures. The field test seeks to provide some standardization in conducting field drop test and evaluating the puncture resistance of geotextiles in the field. Results of the field test were compared with standard index tests currently in use. It was found that existing index tests, like the CBR test and tensile strength test, do not adequately reflect the geotextiles' ability to resist puncture and tear. However, results suggest that the puncture resistance of the geotextile can be evaluated reliably by the Energy Level of the geotextile. © 2004 ASCE.