Stablity of a pebble dam with an injected core

Abstract

1. When it is possible to solve both two- and three-dimensional problems of the state of stress and strain it is expedint for investigating the behavior of earth dams and to use the combined approach based on solving selected two- and three-dimensional problems in a definite way. 2. The results of the calculations show that the three-dimensional behavior of a 122.5m-high gravel dam in a canyon with a site coefficient Ksi∿1 is determined maily by its interaction with the walls, moreover, the dam proves to be substantially underloaded. This can serve as the cause of development of slide processes in the surface zones of the dam (i.e., near the crest and slpes) in the case of insufficient compaction of the soil. 3. The effect of a change in the slope of the downstream face on stability of the dam is small: the stability of the dam noticeably increases when the slope is reduced from m2=1.25 to m2=1.5. A further flattening of the slope hardly increases the stability of the structure. 4. The soil placement density has substantial effect on dam stability. It was found that with high-quality placement of soil with ID∿0.9 stability of the first-phase dam is provided with a high safety factor even when m2=1.25. 5. The results of investigating the effect of soil placement density and slope of the downstream face on stability of the first-phase dam presented in the form of graphs can be used when assigning the parameters of the dam design and soil placement density on the basis of known stability requirements. 6. Although loss of stability in the surface zones of the dam is noted precisely by the three-dimensional problem, the stability characteristics K s t ·st and K s d ·sl obtained on solving three-dimensional problems are substantially (by 1.5–3 times) higher than those obtained on solving two-dimensional problems. 7. Since in the case of poor compaction of the soil a loss of stability occurs in the surface zones of the dam, i.e., near the crest and slopes, stringent requirements should be imposed on soil compaction precisely in these zones; it is also expedient to replace the gravel-pebble fill by fill having a greater strength under small stresses, i.e., by rubble.