The deformation mechanism of a high rockfill dam during the construction and first impounding

Abstract

The Masjed-e-Soleyman Dam is a tall rockfill dam with clay core, located in Iran. During the construction and first impounding, a considerably high excess pore water pressure was developed inside the core and, then, dissipated at a very slow rate; thus, the consolidation deformations were found insignificant. However, there were reports of noticeable internal deformations in the dam, and the crest also exhibited quick settlements during the first impounding. The main objective of this paper is to identify the deformation mechanism of this dam. For this purpose, the data recorded by its instruments were carefully studied and, then, a three-dimensional numerical model of the dam was developed. The mechanical behavior of materials was idealized by a hardening strain constitutive model. A numerical method was proposed based on this constitutive model and Rowe's stress-dilatancy theory to simulate the deformation behavior of coarse-grained materials, such as rockfills, due to particle size distribution, particle breakage, rotation, and rearrangement under shearing. The results show that the significant development of pore pressure in the core and its insignificant dissipation, plastic shear deformations inside the core, and extensive collapse settlements of the upstream shell are the main causes that inuence the deformation mechanism.