Variation of stress-strain state of rockfill dam affected by creeping

Rockfill is subject to creeping and this phenomenon has negative consequences for rockfill dam stress-strain state (SSS). Recently, rockfill creeping attracts more and more attention in China where a great number of embankment dams are constructed. Chinese scientists fulfilled tests of rockfill in stabilometers. However, for SSS numerical modeling, there are used other empirical rheological models whose parameters are determined by the method of SSS back analysis of existing rockfill dams. For studying the effect of creeping on rockfill dam SSS, the authors fulfilled back analysis for Tianshengqiao-I dam in China. Modeling the dam SSS was carried out with the aid of software package MIDAS. Two analyses were performed: without consideration of creeping and with consideration of it. Mohr-Coulomb model was used for description of rockfill deformation. For consideration of creeping, it was added by Maxwell-Kelvin rheological model. Reliability of SSS modeling was provided by selection of soil model parameters from condition of approximate correspondence between design and field displacements. Comparison of two design alternatives of analysis permitted making conclusions on the role of rockfill creeping in formation of the dam SSS. There was determined the share of displacements reached during construction due to time-dependent component of rockfill deformation. For settlements, it was amounted to approximately 20−30%, and for horizontal displacements, it was higher. Creeping affects the character of settlement distribution in a complicated way. This is related to the fact that it causes growth of deformation of two types: shear deformations toward the downstream side and deformations of lateral expansion. In the lower part of the dam, deformations of lateral expansion prevail and in the upper part — share deformations. Such character of displacements may affect reinforced concrete face. Effect of creeping on rockfill stress state is not great and it is mainly related to rather small increase of tangent stresses.