Simulation of collapse settlement in rockfill material due to saturation

In the first impounding of rockfill dams, additional settlements occur in upstream side in saturated rockfills due to collapsephenomenon even high rainy seasons can cause additional deformation in the dumped rockfills. Unfortunately thesedisplacements are not taken into account in the conventional numerical models which are currently used to predict embankmentdam behavior during impounding. In this paper to estimate these displacements, strain hardening-strain softening model in Flacis modified based on the laboratory tests, in which same impounding process in such dams is considered. Main feature of the model is reproduction of nonlinear behavior of rockfill material via mobilized shear strength parameters and using collapse coefficient to display induced settlement due to inundation. This mobilization of shear strength parameters associated with some functions for dilatancy behavior of rockfill are used in a finite difference code for both dry and wet condition of material. Collapse coefficient is defined as a stress dependent function to show stress release in the material owing to saturation. To demonstrate how the model works, simulation of some large scale triaxial tests of rockfill material in Gotvand embankment dam is presented and results are compared with those from laboratory tests, which are in good agreement. The technique could be used with any suitable constitutive law in other coarse-grained material to identify collapse settlements due to saturation.