ROCK MASS QUALITY EVALUATION IN BAKHTIARY DAM SITE USING SEISMIC METHODS

6th International Scientific Conference - SGEM2006, www.sgem.org, SGEM2006 Conference Proceedings/ ISBN: 954-918181-2, June 12-16, 2006, Vol. 1, 141-152 pp

ABSTRACT

This paper present a geophysical investigation performed for the Bakhtiary dam site in Iran. As it has been designed with 330 meter high, this dam would be the highest dam in the world. In the context of engineering seismology, seismic tomography may be relevant in problems where seismic refraction is currently used. Both of these techniques aim to detect subsurface velocity.
In Bakhtiary dam site we used seismic refraction, tomography and borehole seismic tomography methods. For refraction seismic method Geotomo software that employed the time-depth and seismic velocity analysis function of the generalized reciprocal method (GRM) was used. Six exploration Gallery and two boreholes are drilled in Bakhtiary dam that GR1, GR2, GR3 are in right abutment and GL1, GL2, and GL3 are in left abutment. Cross-hole, cross-galleries and also between main and inlet of galleries seismic tomography were designed and surveyed. We used Geotomo software that employed the LSQR method for inversion problems which is commonly used in travel time tomography. Velocity images in GR2 and section of GR2-GR3 show very low velocity. The result of velocity images obtained by the borehole tomography is compared with geology surveying and rock mechanic experiments. It is found that velocity images are in a good agreement with rock mechanics data and geology surveying.

Keywords: Bakhtiary dam, Refraction seismic, Seismic tomography, Rock mass quality, P-wave velocity.