GEOCHEMICAL CHARACTERISATION OF THE OUTCROPPING ROCK MASSES THE IMMEDIATE VICINITY OF WADI EL-KAFFREIN DAM SITE (JORDAN)

this paper, the geomechanical characteristics of the discontinuities present in the rock masses, exposed in and around the existing Kaffrein dam site (Western ~,Jan), have been investigated for a probable heightening project of the dam in the near future. r this purpose, eighteen detailed line surveys were carried out to determine the geometrical and the mechanical properties of the discontinuities. These .tions were located on both the abutments as well as on the exposed rocks near the reservoir area. lalysis of the discontinuity orientations, plotted on equal-area stereographic contour nets, have indicated the presence of two sub-vertical joint sets and a rd one attributed to bedding planes. On the one hand, right abutment rock masses are characterised by low persistence, closely spaced joints that caused e formation of small to very small block sizes. On the other hand, exposed rocks on the left abutment reflect the presence of closely to widely spaced, oderately persistent joints which result in small sized blocks. ':k mass Uniaxial Compression Strength (UCS) was determined both in the laboratory and in situ. In situ measurements classified the rock masses as :~g, while those measured in the laboratory, classified the rock masses as weak to moderately strong. Low UCS values were assigned to samples taken n the left abutment. Such values (UCS < 20 Mpa) are believed to be questionable in view of the large difference observed between these values and those .~i.ned from in situ measurements (UCS = 80 MPa). -k mass shear strength behaviour of the studied rocks was estimated considering the JRC, JCS of the main discontinuity sets as well as the empirical ,uulae of Barton and Choubey (1977). The estimated shear strength envelopes relevant to the rock masses of both abutments were similar, and thus, they .:sent similar shear strength characteristics. These results indicate the necessity of conducting further laboratory tests on samples to be taken from the left butment in order precisely to determine the spatiel variation of the shear strength parameters, taking into consideration that future works, regarding the ~illway heightening, are to be done on the left abutment. ock mass quality was determined through the employment of the two widely known geomechanical classification systems : RMR and Q. Both systems ssigned a fair to good quality class to the rocks of both abutments. The cross correlation of their results gave a regression equation that is closely similar to tat of Bieniawski. However, it should be stressed that its validity is applicable, preferably, to the study area. ~e geological and geomechanical investigations, presented in this work, established two main problems that are directly related to the dam arts/or to any ; :ure developments or works related to it. The first, concerns the heterogeneous nature, from the fracture intensity point of view, of the rock masses of the ! rnmar formation. While the second, concerns the permeable alIuvial deposits which cover the reservoir area, through which, an unallowable quantity of ping water is taking place. ',e conveyed results are believed to furnish valuable technical information regarding the geomecbanical behaviour of the exposed rock masses in the vicinity ' ~he dam. This information could be used to direct or to lead future field &/or technical works in an efficient way in order to pass to the design and execution :ases.