Analysis Of Possible Relationships Between Seismic Properties And Some Of Rock Mass Geomechanic Properties Of The Outcropping Carbonate Rock Masses In Wad1 El-Kaffrien Dam Site (Jordan)

A seismic refraction and a geomechanic surveys were employed in the investigation of possible<br>relationships that may exist between elastic and geomechanic parameters of a number of outcropping carbonate<br>rock masses in the Wadi El-Kaffrein dam site, western Jordan. Seventeen seismic profiles were conducted<br>across the top of vertical exposures where the underlying geologic and structural conditions are quite visible to<br>be studied in detail. Therefore, the correlations could thus be correctly assessed.<br>The above mentioned prospections were completed on limestones, marly- and dolomitic limestones of the<br>Upper Cretaceous age. The seismic survey enabled the determination of the P- and S-wave velocities, the<br>dynamic elastic moduli, in addition, to a number of seismic ratios. While the geomechanic survey resulted in<br>the quantification of some of the geomechanic characteristics of the discontinuities present in the rock masses,<br>in addition, to the assessment of their overall qualities through the employment of two of the widely used<br>classification systems, namely, RMR and Q.<br>The obtained data were subjected to a bi-variate and multi-variate statistical analyses, so that possible<br>correlations could be evidenced. Such analyses considered eighteen seismic and geomechanic properties. The<br>analysis procedure started by investigating the seismic parameters themselves: Vp, Vs and the dynamic elastic<br>moduli, then these latter parameters were correlated to some of the geomechanical properties. Such<br>correlations led to the development of a preliminary classification system for the assessment of rock mass<br>quality, based upon seismically derived parameters as well as Jf and Jn. The system divides the rock mass in<br>five classes of quality.<br>Concerning the correlations conducted between the RMR- and Qquality indices and the geoseismic<br>parameters, it resulted that the RMR-indices correlate better to the seismic parameters.<br>Results of the multi-variate regression analysis show that the following geomechanic properties could be<br>estimated with a good approximation: Jn, Jf and RMR, while the prediction of RQD and Q indices can’t be<br>predicted from seismic parameters.<br>The study resulted in the individuation of zones or sectors that present a high grade of fracturing and/or<br>lithologic heterogeneity. More in detail, such sectors are located on the left abutment of the dam, where further<br>works should take place if the dam’s height will be increased. Moreover, the obtained bi-variate and multivariate<br>regression equations furnish a wealth of information upon which extrapolation of geomechanic<br>properties to other areas can be based.