Filtration Bypassing Retaining Hydraulic Structures

Concrete dams that are part of river waterworks are integrated with earthworks or with banks using coastal abutments. If the soil of cost or earthen dam is permeable, then in the zone of contiguity water filtration occurs around the coastal abutment. Calculation of filtration bypassing the coastal abutment at specified water levels in the upper and lower pools is performed with the aim of constructing an encircling curve of depression and determining a gradient of filtration flow that controls the filtration strength of the soil beyond the abutment. This problem has no theoretical solutions – in view of its complexity, approximate calculation methods have been developed for individual calculation schemes. For the case when the soil behind the coastal abutment is homogeneous and isotropic, groundwater inflow from the coast is absent or insignificant and can be neglected, and the coastal abutment is located on a water bed and approximate methods by V. P. Nedrigi and R. R. Chugaeva are proposed in the paper. The experience of surveying a number of Belarusian hydropower stations has shown that the absence of a justified prediction pertaining to the position of groundwater levels beyond the estuary leads to a decrease in the strength and stability of the coastal abutment and its possible destruction. An experimental verification of the approximate method for calculation filtration bypassing the coastal abutment developed by R. R. Chugaev has been carried out in laboratory conditions. According to the obtained experience a depression curve encircling the abutment has been constructed which show good agreement between experimental and calculated data that allows to use this method for reasonable design of coastal abutment structures ensuring their reliable operation.

DOMESTIC EXPERIENCE OF ASSESSING THE FILTRATION STRENGTH OF NON-COHESIVE SOILS OF DAM BODY AND BASE

The article considers a retrospective of study of the filtration stability of non-cohesive (sand and gravel) soils carried out by specialists of the Soviet and Russian periods. These are the works of hydraulic scientists: Izbash S.V., Patrashev A.N., Chugaev R.R., Istomina V.S., Pavchich M.P., Pravedny G.H., Lubochkov E.A., Burenkova V.V., Zhilenkov V.N. and others. There is given a detailed description of characteristic features of the operation of filters and drainages of hydraulic structures, earth dams, dikes, other water retaining structures. Numerous approaches to the suffusion processes in sand-gravel soils are generalized. The description of filtration deformations of non-cohesive soils is given: suffusion, colmatation (colmatage), penetration-spillage, erosion and flooding and rebounding. It is shown that in their calculations the authors of dependencies operate such characteristics of soils and filtration as the diameter of particles, gradient and water speed. It is stressed that in modern regulations the allowed natural gradient in a ground construction is determined with a reserve factor, depending on the class of the structure.