Segregation test—a standardisable test for suffusion assessment of granular soils

Abstract

Suffusion is arguably the most complicated type of internal erosion. Although there are several popular assessment methods, the most realiable assessment is possibly still laboratory testing. However, there is not a standardised test for suffusion yet as different laboratories use different equipment and test configurations. Hence, a reliable comparison of outcomes across laboratories may not be able to achieve yet. This paper presents a new and simple, but very effective, way to test the susceptibility of soil to internal erosion using a novel segregation test. The test employs standard equipment which can be easily found in any geotechnical laboratory. There are some common characteristics of internal erosion and transport segregation, where fine particles are transported through the pore constrictions formed by the soil’s primary fabric. In segregation, particles are transported by gravitational/mechanical force to the bottom of the soil mass. Meanwhile, they are washed out of the soil mass by hydraulic force in internal erosion. Laboratory testing for internal erosion often requires specific equipment and a long duration. Meanwhile, segregation test could be undertaken with standardised sieving tower, which is available in any geotechnical laboratory. The approach was verified with an acrylic setup and some 3D-printed details. Later, the tests of 25 mixtures were undertaken with standard sieving sets. The correlation of laboratory results shows good agreement and prompts the common application of the new approach. The new test may not be able to completely replace the conventional suffusion test yet as it overlooks the critical hydraulic gradients at this stage, but it can be very useful if the research focuses on only the erodible mass and susceptibility to suffusion. In addition, it is a standardisable test with no specific requirements on equipment. The new approach may also be a starting point to study other types of internal erosion.