Triaxial Erosion Test for Evaluation of Mechanical Consequences of Internal Erosion

This paper presents a newly developed triaxial apparatus to directly investigate the mechanical behavior of eroded soils. Efforts are devoted to maintaining the back pressure in the tested specimens to ensure a relatively high degree of saturation during the erosion test. Instead of determining the cumulative eroded soil mass by the method of collecting and drying effluent at discontinuous periods, a consecutive monitoring system is installed to permit continuous recording of the eroded soil mass. Gap-graded non-cohesive soils, which are vulnerable to internal erosion, are tested. Erosion tests are performed by the constant-flow-rate control method with the measurement of the induced pressure difference between the top and bottom of the tested specimens under the preferred stress state. Volumetric strain of the 70-mm-diameter, 150-mm-high specimen is monitored during the erosion tests. The mechanical consequences of internal erosion, in terms of the stress–strain relationship, are evaluated by conducting monotonic compression and cyclic tests on the eroded soils. The test results reveal that internal erosion would cause the increase of hydraulic conductivity and volumetric deformation of the tested specimens. Internal erosion would mainly induce the reduction of the drained compressive strength. The undrained peak deviator stress of the soil that suffered from internal erosion is higher than that of the soil without erosion. Undrained cyclic tests indicate that, compared to the soil without erosion, the eroded soil would fail after more cyclic loops.