Grout curtain in the foundation of the earth dam of the Maina hydroelectric station

Conclusions

• 1. The grout curtain was made under conditions of a head on the damp up to 12.5 m under the protection of a temporary blanket placed on natural alluvium; the blanket reduced the gradients of the head in the zone of grouting and provided normal conditions of conducting it.

• 2. The combined method of grouting used made it possible to save materials and reduce the estimated cost of the curtain by 30%. The use of the packerless method of grouting can be recommended for barrier rows of the curtain when the initial permeability of the soil is greater than 100 m/day in combination with the packer method of grouting of the central rows.

  The results of control tests showed a high density of the grout curtain (permeability coefficient within limits up to 0.5–1.0 m/day).

• 3. The new “moving pipe” method proposed by Soyuzgidrospetsstroi together with Gidrospetsproek and tested at the Maina hydrostation showed results close to packer grouting and, as a consequence of this, the possibility of its use. But, with consideration of the insufficient volume of works performed by the moving pipe method (2% of the total amount of grouting), its further testing at other objects is recommended.

• 4. The design of the packer strings with rubber packers flush with the pipe surface provides tightness and cleanness of the string and is recommended for further use.

• 5. Grouting experience confirmed the expediency of placing a concrete covering at the site of the works, crated by the separate concreting method.