Sagging and filtration behaviour of nonwoven geotextiles overlying different bedding materials

This paper presents and discusses the results obtained in laboratory tests to evaluate sagging and filtration behaviour of nonwoven geotextiles overlying particles of different bedding materials. Nonwoven geotextiles with masses per unit area of 200 g/m2, 400 g/m2 and 600 g/m2 were used in the tests. Stainless steel spheres and gravels were employed as granular materials underlying the geotextile filter. Specific tests to evaluate the intensity of sagging of the geotextile filter in the voids of the underlying material were carried out. Average strains mobilised in the geotextile were assessed in the tests. The grain sizes of the particles that piped through the geotextile filter for different arrangements of spheres as bedding layer for the filter were measured. The results obtained showed that bedding conditions and geotextile structural characteristics can influence its retention capacity. Good comparisons between predicted and measured average geotextile strains were observed.