Owing to an increasing demand for water in the western provinces of Iran, the inevitability of dam construction on karstic foundations cannot be avoided; recent dams have been built on soluble, karstified, weathered, fractured, faulted, and folded rock foundations. To ensure the permanent stability of these dams, the first task is to investigate the characteristics of the underlying ground. The proposed Kangir dam site is located in western Iran (Elam Province). The geotechnical properties of soluble rocks at this site, as determined from laboratory tests, are the subject of this article. The foundation rocks comprise some limestones (Asamri Formation) and, to a greater extent, strata (Gachsaran Formation) containing marl, gypsum-bearing-marl, and gypsum. The lithomechanical characterization of the rocks included comprehensive engineering geology and rock mechanics studies conducted at the site including surface geology, jointing fabric study, borehole drilling and logging, and field and laboratory geotechnical testing. Laboratory tests on core samples were carried out to delineate the physical and geomechanical properties of the intact rock at the proposed dam site, using ASTM standards and ISRM suggested methods.
1. INTRODUCTION
Water flowing through fractures in soluble rocks widens these through dissolution, a process known as karstification. Karstic terrain is a characteristic feature in the west of Iran along the Zagros Mountains because of vast areas of soluble rocks such as limestone and gypsum. Because of their flow pattern complexity, karst areas are considered problematic as construction sites for large dams. Owing to an increasing demand for water in the western provinces of Iran, dam construction on karstic foundations cannot be avoided; recent dams have been built on karstified, weathered, fractured, faulted, and folded foundations. To ensure the permanent stability of these dams, the first task is to investigate the characteristics of the underlying ground. In this article we highlight results of a comprehensive geotechnical and rock mechanics study carried out at the proposed Kangir dam site. This site is located in west of Iran (Elam Province) and will impound flow from the Kangir River. The study area is part of the folded Zagros area, a well-known active tectonic belt stretching north-west from south Iran. The foundation rocks comprise some limestones (Asamri Formation) and, to a greater extent, strata (Gachsaran Formation) that contain marl, gypsum-bearing-marl, and gypsum. Karstification is widespread in the limestone and gypsum units. Rock characterization included engineering geology and rock mechanics studies carried out at the site and surrounding areas, and included surface geology, jointing fabric study, borehole drilling and logging, and field and laboratory geotechnical testing. Laboratory tests on core samples were carried out to delineate the physical and geomechanical properties of the intact rock at the Kangir dam site. For the different rock units exposed in the study area, parameters such as dry density, saturated density, porosity, durability index, uniaxial compressive strength (UCS), shear and compressional wave propagation velocity (vS, vP), and water absorption ratio were determined in the laboratory based on ASTM standards and ISRM suggested methods.
