Parameters of non-linear models of soil for analysis of stress-strain state of a rockfill dam

Introduction. Calculations of stress-strain state (SSS) of the first and second classes embankment dams are required to be carried out using non-linear models of soil. Such models include the Hardening Soil model (model HS) and Mohr – Coulomb model (model MC). It is important to determine the parameters of these models for coarse soils: crushed stone and gravel-pebble.

Materials and methods. Parameters of the HS model for coarse soils were determined by processing of the results of triaxial tests, which are presented in foreign publications. Parameters of the MC model were determined from condition of the SSS approximate correspondence of a high dam (100 m high) obtained by using two models. Stress-strain state of the dam was determined by means of numerical modelling in the PLAXIS 2D software package.

Results. HS model parameters are selected; which allow satisfactory description of soil behaviour at deviatoric loading; noticeable deviations are revealed only in values of volumetric deformations. Comparison showed that crushed stone whose test results are used for determination of models’ parameters, refers to properly compacted soil of modern rockfill dams. When selecting the parameters for the MC model, which are equivalent to the HS model, the results of rockfill dam numerical modelling were checked both in deformations and in stress-strain state. At the dam SSS formation there vividly revealed the effect of soil “hardening”: at the stage of perceiving hydrostatic pressure the soil deformation sharply decreases as compared to the stage of loads from the dead weight. Therefore, it is reasonable to select parameters of the MC model separately for two stages of the dam loading.

Conclusions. The HS model in general makes it possible to reflect non-linear deformations of coarse soils, however, it does not take into account the curvilinear character of the limiting surface and cannot simultaneously reflect the phenomena of contraction and dilatancy. Use of the MC model does not permit adequate simulation of rockfill dam SSS; the selected parameters of the MC model may be used only for approximate calculations.

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