EARTH CORE ROCKFILL DAM: INTERACTION OF WATER AND SOIL

Accuracy of results of numerical modeling of the structure stress-strain state (SSS) depends on adequacy of design scheme. At elaboration of design scheme of an embankment dam the important aspect is selection of force loads from water. Water medium may create several types of force loads on the dam: hydrostatic pressure, buoyancy and seepage volumetrically distributed forces, as well as arise internal pore pressure in soil. Selection of design scheme of the earth core rockfill dam depends on permeability of the clayey soil of the seepage-control core and the speed of the seepage regime formation. Analysis of the field observations over the state of constructed dams showed that this process may occur in different ways. In some dams after the reservoir impoundment the seepage regime is installed relatively quickly, in other dams there takes place a durable process of pore pressure dissipation and soil consolidation. For estimation of the effect of the form and method of loads application, the analysis of the stress-strain state of high earth core rockfill dam for three design schemes was carried out. These are cases with conditionally impermeable, well permeable and scarcely permeable core soil. In the first case the core is subject to hydrostatic pressure, in the second to the force from the steady regime of the seepage flow, in the third, inequality of pore pressure and seepage forces takes place. For analysis there was used the software package MIDAS, which permits conducting combined analysis of SSS and seepage regime, solving tasks related to consolidation of soils. Coulomb-Mohr model was used for modeling of soil. Analysis showed that the dam SSS in three design schemes varies greatly. The dam is subject to the highest pressures and deformations in the case of the impermeable core at the action of hydrostatic pressure. The dam SSS at well permeable core, where seepage flow quickly becomes steady, is more favorable. The case of scarcely permeable soil is unfavorable from the point of view of core crack resistance. Due to core pressure, buoyant and seepage forces the stresses in soil skeleton are small. At that, horizontal displacements of the dam by value are closer to displacements in case of water impervious soil. This frequent case may be the most dangerous for the dam safety.