Calculation of earth dams being undermined

Abstract

At present many dams and embankments of reservoirs and slime ponds are located in zones of underground mining. To ensure reliability of these structures it is necessary to predict the changes in their stresses upon displacement of the ground surface from undermining causing relative horizontal compressive and tensile deformations in the surface layer of the rock mass. Especially dangerous for earth dams are deformations due to spreading (extension) of the ground surface, which are characteristic for the marginal part of a subsidence trough [i, 2]. In the first approximation these deformations can be taken on the basis of the results of actual measurements and in calculations can be regarded as the initial data independent of the parameters of the dams.Deformations of the foundations underlying earth fill (dam, embankment) inevitably cause the occurrence in it of regions of a limit stressed state, the dimensions of which are determined by the magnitudes of the deformations and strength parameters of the fill soils. In [3,4] the stressed state of fill on spreading foundation is assumed determined according to V. V. Sokolovskii's theory of a granular mass on the assumption of a limit (plastic) state of the entire fill. In this case practically important problems of the development of the zone of limit equilibrium and determination of the magnitudes of deformations of the foundation converting the fill completely to a plastic state remain unsolved. Calculations of the state of stress and strain of earth fill under any loads up to breaking on it becomes possible on solving the mixed problem of the theories of elasticity and plasticity, which takes into account the occur=ence and development of regions of a limit stressed state of soil, and taking for it a unified model of the elastoplastic medium at all loading stages. The formulation of this problem within the scope of the theory of plastic flow with the use of the associated and unassociated laws for plastic deformations developing in regions of limit equilibrium is e~_m~ned in [5, 6] for variants of plane and volume strains of a soil medium. In the adopted model the soil is conceived as a continuous medium in a prelimlt (elastic) state, linearly or nonllnearly deformable and passing into a llmlt (plastlc) state in conformity with the strength condition used. In this case the physical relations between the stress and total strain vectors are taken in incrementsis a physical matrix equal to [D e ] in zones of the prelimit and to [DP] in zones of the limit state of the soil. The expressions for [D e] and [DP] are given in [5,6]. The algorithm developed there for numerical solution of the mixed problem on an electronic computer calls for using step (graduated) loading and the finlte-elementmethod (FEM), and as applied to problems of plane strain is realized in a program for a BESM-6 computer.It calls for using in [D e] variable shear moduli G and volume strains K (or modulus of deformation E and poisson's ratio ~) at the loading steps and a variable (depending on densi...

Ensuring the Reliability of Earth Dams in Complex Hydrogeological Conditions

“…In the problem under consideration to the usual problems of designing earth dams (the study of the geomechanical properties of compressibility and permeability of the soil, the study of the stress-strain state, the filter strength evaluation, static and dynamic stability, etc.) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Overlap completely new, not previously encountered, the problem of reliability of embankment dams in extreme conditions, under the influence of new additional load in the form of intense deformation and curvature of the base extension.…”