Assessment of the Ortachala HPP low head dam abutment deformation and seepage regime

Abstract

During Ortachala HPP operation period cracks were formed in the right-bank of foundation, where is located underground fish-way sections. Right bank dam-foundation contact opened only in the horizontal direction, that caused 5.5 cm gap development, while there were no changes in the vertical direction. Visual researches showed that cracks (size is 4–5 cm) developed in fish-way construction. Mathematical models: fish-drainage-foundation, retaining wall-drainage-foundation, with the use of the finite element scheme, allowed us to finalize the suffusion-deformation process developed during the operation, namely: in the cracking zones of fish-way developed high gradients of seepage pressure, causing suffusion; under the influence of the weight of the soil and transport, shrinkage of the soil developed, which for the foundation of the right bank, created bending deformations causing the rotation of the soil in the vertical plane; bending deformation of the foundation at the contact of the concrete structure and the embankment caused a horizontal opening, spread out – at a depth of 4m. In connection with this, the retaining wall, leaning against the ground, loses support and, under the influence of hydrostatic pressure, tensile stress develops in it. In the case of crack formation in the wall, concentrated seepage will develop, which will cause groundwater rise in the main road and various unfavourable processes. Having established the reason for opening the contact, the fish was closed, as a result of which above mentioned process was stopped. Thus, the waterproofing of the fish-way is a necessary measure for the normal operation of the waterworks.