Improving the geotextile filter design criteria for internally unstable cohesionless soils

The behaviour of a geotextile filter in contact with internally unstable cohesionless soils depends on interaction between filter pore size distribution and base soil particles and on fraction of particles free to move inside soil skeleton. These particles can accumulate at soil-filter interface leading to blinding or remain entrapped within filter pores leading to clogging or pass through geotextile. The openings of geotextile should allow the passing of soil particles not belonging to soil skeleton keeping the same stable to avoid base soil erosion and minimize the geotextile filter clogging and/or blinding. The upper limit of filter characteristic opening size meets requirement of retention criterion while the lower limit of filter avoids blinding and/or clogging phenomena. Among different geotextile filter design criteria for internally unstable cohesionless soils, Moraci (1996) criterion considers as lower limit of filtration opening size the critical diameter of suffusion. In this paper, a database of many soil-geotextile filtration tests, for which this criterion has not yet been tested, was created to assess its reliability, compared to other existing design criteria. Finally, a new methodology proposed recently by the Authors is also applied to evaluate internally unstable cohesionless soil-geotextile filter compatibility to all interfaces analysed in database. • Particles free to move in bordering pores in internally unstable cohesionless soils. • Lower limit of geotextile filter design criterion for internally unstable cohesionless soils. • Application of a geometrical, experimental and microstructural new methodology. • New approach to design geotextile filters in contact with internally unstable cohesionless soils.