Effect of the initial state of skeletal-clay soil on its deformability and strength

Abstract

Experimental investigations show the effect of the iuidal state of ard~eially compacted clay soil on the operation of a core or other watertight element in a high-head earth dam. The problem of designing the initial state is considered using as the example the experience of cons~cting the Nurek dam core and is solved on the basis of a comprehensive study of the mechanical properties of the soil for the case of a three-dimensionalstressed state of triaxial compression. As a result of layer-by-layer mechanical compaction of the soil it is necessary to obtain the required artificial structure and state of the soil for the design grain-size distribution. Its mechanical and seepage properties, which determine the regularities of development of the stress-strain state in the core during construcrion, introduction into operation, and subsequent long-term operation, depend to a considerable extent on this structure. A special feature of this article is the comprehensive study of the mechanical properties of clay at different stages of load resistance in a state of triaxial compression. The results of long-term investigations of soils in the prelimiting stage of loading and during flow, carried out at the V. V. Kuibyshev Moscow institute ofC ivil Engineering, are used. In this lies the theoretical interest of the presented solution of the applied problem of constructing impervious elements in high-head earth dams.

Engineering generalizations of an investigation of the effect of the time factor on long-term strength and deformability of clays of high-head earth dams

“…The inherited effect of deformation processes in the prelimit state on the regularities of the flow is determined by previously established relations between the joint effect of the time factor and loading trajectories for various initial soil states [5,6]. The inherited effect of deformation processes in the prelimit state on the regularities of the flow is determined by previously established relations between the joint effect of the time factor and loading trajectories for various initial soil states [5,6].…”

“…Under these conditions it was expedient, relying on certain principles of the theory of limit states of a structure, to use the engineer's usual strength concepts in a study of the long-term strength of soil, but to study it with consideration of nonequilibrium processes in the presence of a variable stress, which are determined by the characteristics of the effect of the time factor for the given engineering problem [1][2][3][4][5][6][7].Numerous soil investigations and, in particular, the investigations we performed on earth dams, have established the significant role of the history of loading in the prelimit region, hereditarily influencing the critical state of the long-term strength and regularities of subsequent flow. The result of soils in a prelimit (elastic) state are undergoing a long-time nonequilibrium state of structural transformations, which radically influence their strength and deformability at various stages of dam construction and subsequent long-term operation.…”

“…Under these conditions it was expedient, relying on certain principles of the theory of limit states of a structure, to use the engineer's usual strength concepts in a study of the long-term strength of soil, but to study it with consideration of nonequilibrium processes in the presence of a variable stress, which are determined by the characteristics of the effect of the time factor for the given engineering problem [1][2][3][4][5][6][7]. The theory of creep of a continuous soll medium, as is known, does not include analogies with respect to the state equations reflecting the listed characteristics of the problem being considered, and phenomenological knowledge of the necessary regularities is quite limited.…”

Experimental study of the mechanisms of deformability and flow of soil under conditions of the two-dimensional boundary-value problem with respect to strains

“…12, 13, 14, and 15 that under the conditions of the boundary-value problem the main regularities of the flow that were established under conditions of uniform isotropic compression of the specimens in different regimes of loading and prescribed stress trajectories are preserved [4,5]. However.…”