Behaviour of geotextile filters in armoured slopes subjected to the action of waves

Geotextile filters can be used in several geotechnical and geoenvironmental applications. Regarding the protection of banks or slopes against erosion caused by the action of waves, these materials can be employed under revetments and armour layers. This paper presents results of large scale tests on armoured slopes where geotextile and granular filters were employed. A wave flume was used in the tests and three types of nonwoven geotextiles and a conventional granular layer were employed as filters between the armour layer and the base soil slope. The armoured slope was subjected to the impacts of waves produced by a wave generator opposite to the channel slope. Pore pressures in the soil slope were measured during the tests and soil particles that piped though the filters and that were entrapped in the geotextile were collected for total mass and particle diameter measurements. The results obtained showed that the geotextile and the granular filters presented similar performance. In addition, retention criteria available for this type of geotextile filter application provided very conservative results. The findings highlight the importance of the development of more accurate testing techniques and filter criteria for designing armoured slopes with geotextile filters.