Placement of alluvial sands in the channel dam of the Tyuyamuyun hydro development

Abstract

1. With layerwise placement of sand with rolling the placement density is 0.10 g/cm3 higher than with the hydraulic-fill method of placement. 2. Placement of sand with rolling by 25–30-ton pneumatic-tire rollers should be done in layers of 30 cm each and compacted in six passes. In this case the value of the optimal moisture content of compacting the sand is 10–14%. 3. Soils in hydraulic-fill stockpiles are inhomogeneous with respect to compactibility, which is related to the technology of hydraulic filling of the stockpiles. With approach to the discharge wells the soil is finer and more inhomogeneous. With increase of the content of coarse fractions greater than 0.25 mm in the soil composition to 50–60% its compactibility increases. With increase of the content of coarse fractions to more than 60% the value of the unit weight decreases. 4. The required placement density of fine and medium sands, analogous to the alluvial sands of the Amu Darya floodplain, can be assigned both on the basis of the data of standard compaction by an impacter (based on the maximum density without introduction of correction factors) and on the basis of the data of experiments to determine the densest possible state (with the introduction of reducing coefficients according to the technical and economic feasibility study taking into account the technology of hydraulic filling, dynamic strength of the slopes, etc.).