Advertisement

An appraisal of the test grouting data for the Tehri Dam, India

  • Shome S. K. 
  • Kumar V. 
  • Gupta U. P. 
Article

Abstract

Test grouting has been carried out in the three different rock units (phyllites grade I, II & III) exposed around Tehri Dam Project to evaluate the groutability of these rocks and to evolve optimum spacing of grout holes to be adopted for the grout, curtain. Since it has been observed that permeability of the rock mass is essentially secondary and is mainly joint and fissure controlled, the structural discontinuities observed in the rock types have been analysed for finding out the direction of grout holes that can intersect the maximum numbers of discontinuities and hence seal the rock mass properly. The grouting has been carried out through grou holes and its effectiveness has been observed through inspection holes drilled in between and depending upon the effectiveness, secondary and tertiary holes were drilled in between to reduce the spacing of holes from inspection holes. Finally, when the permeability values of inspection holes were reduced to 1 lugeon or less after grouting through tertiary holes, it has been considered to have achieved optimum grouting efficiency. The effective grout travel distance in the phyllites has been proved to be 0.75 m. It has been inferred that adoption of high grout pressures while emplacing the grout curtain might change the spacing to around 1.5 m apart.

Keywords

Rock Mass Shear Zone Rock Unit Grout Curtain Structural Discontinuity 

Estimation des injections nécessaires pour le barrage de Tehri, Inde

Résumé

Des essais d'injection ont été réalisés dans trois types différents de roches (phyllites I, II et III) sur le site du projet de barrage de Tehri, afin d'évaluer les capacités d'absorption de ces roches et pour calculer l'espacement optimal des forages d'injection pour réalisation du rideau d'étanchéité. On a observé que la perméabilité du massif rocheux est essentiellement secondaire et dépend surtout des joints et fissures. Les discontinuités de structure ont donc été analysées pour trouver les meilleures orientations possibles pour les forages d'injection, de façon à recouper le plus grand nombre possible de ces discontinuités et ainsi sceller au mieux le massif. L'injection a été réalisée dans des forages d'injection et son efficacité a été observée à l'aide de forages d'inspection intercalaires et dans certains cas des forages supplémentaires ont été rajoutés, en fonction des résultats observés. Finalement, on a considérés que lorsque la valeur de la perméabilité a été réduite à moins de 1 lugeon après injection dans les forages supplémentaires, l'efficacité optimale était atteinte. L'écartement optimal des forages d'injection dans les phyllites s'est avéré être de 0,75 m. On en a déduit que l'adoption de pressions d'injection élevées lors de la mise en place du rideau pourrait permettre d'adopter un espacement de 1,5 mètre.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. [1]
    AUDEN J.B., 1934: Geological Survey of India, Rec. Vol. 77 E 78, part.-2.Google Scholar
  2. [2]
    FERGUSON F.F. and LANCASTER-JONES, P.E.F., 1964: Testing the efficacy of grouting operation at dam sites: Proceedings of 8th international congress on large dams, Edingbugh, U.K. Vol-I, pp. 121–140.Google Scholar
  3. [3]
    GRANT L.F., 1964: Application of unit take concept in evaluationg grout hole drilling mehods: Engg. Geology Vol. I, No. 1, pp. 52.67.Google Scholar
  4. [4]
    KLOSTERMAN, MICHAEL J., WOLFF, THOMAS F., and JAHEER, NEELS G., 1982: Quantitative relationship of grouting to the reduction of ground water flow through rock foundation Bull of Assoc. of Engg. Geologist Feb. 1982 Vol. XIX, No. 1, pp. 15–24.Google Scholar
  5. [5]
    PANT G., NARULA P.L. and SHOME S.K., 1969: Geotechnical studies relating to the planning and design or Tehri Dam Project, A summary of the investigations carried out from 1961–62 to 1967–68. Unpublished progress report, Geological Survey, of India Vol-IV, p. 154.Google Scholar
  6. [6]
    SHOME S.K. and KUMAR V., 1979: Geology and foundation treatment of the Tehri Dam Project, Uttar Pradesh India, Proceedings of workshop on Tehri Dam Project, Dec. 4th to 6th 1979, Vol. I, pp. 1.28.Google Scholar
  7. [7]
    SHOME S.K., 1979: Study note detaining the proposal of a programme of test grouting at the Tehri dam: Unpublished Geological Survey of India Note.Google Scholar
  8. [8]
    SINCLAIR B.J., 1972: Estimation of grout absorption in fractured rock foundation: as referred in Klostermanet al (1982) in reference No. 4.Google Scholar
  9. [9]
    SNOW D.T., 1968: Rock fracture spacing, opening and porosities. J. Soil Mech. Found Divn. Amer. Soc. Civ. Engg. 94, pp. 73–91.Google Scholar

Copyright information

© International Assocaition of Engineering Geology 1988

Authors and Affiliations

  • Shome S. K. 
    • 1
  • Kumar V. 
    • 1
  • Gupta U. P. 
    • 1
  1. 1.Engg. Geology DivisionGeological Survey of India. Northern RegionLucknowIndia

Personalised recommendations