Back-Calculation of a Failure in Multilayered Stacked Geotextile Tubes Using DEM-CFD

The geotextile tube provides a cost-effective alternative for constructing containment structures, while tailings and coal ash disposal are relatively new fields of application. However, the performance of multilayered stacked geotextile tubes is still poorly understood. A coal ash levee, which was constructed in two stages (namely primary levee and upper levee) using multilayered stacked geotextile tubes, failed as a result of backward erosion piping (BEP). To promote an understanding of the performance of multilayered stacked geotextile tubes, in this study, a postfailure investigation was carried out by multiscale modeling with the transient fully coupled discrete-element method and computational fluid dynamics (DEM-CFD) approach. The geotextile tubes at the downslope toe deformed significantly due to BEP and subsequently triggered a retrogressive sliding deformation to the overburden geotextile tubes of the primary levee but not of the upper levee. This suggested that the multilayered stacked geotextile tubes exhibited a strong resilience against a global failure. The critical slip surface was more inclined to a block failure instead of a circular failure. A sensitivity analysis indicated that increasing the interface friction coefficient between geotextile tubes, µg-g, can significantly enhance the stability of the levee against sliding and reduce the likelihood of significant deformation.