ASSESSEMENT OF SOLUBILITY OF ASMARI LIMESTONE IN KARUN1 DAM SITE

Solubility of limestone plays a great role in karst engineering, particularly in relation to hydraulic structures in karst areas. This paper is concerned with the geothechnical assessment of the influence of the aperture of joints and infilling materials on the solubility of limestones. It has been shown that the safe maximum size of joints for a given hydraulic structure can be calculated from the solution parameters of rock. The method of assessment of solubility was based on laboratory works on the core samples of Asmari limestones from Karun1 (Shahid Abbaspour) dam site in Iran. The rate of solution of samples was measured using solution of carbon dioxide of different concentration. The solution rate constant of limestone samples was Kc = 3.15 x 10^-7 cm/s. The results of laboratory experiments (XRF) on core samples of Asmari limestone showed calcium oxide is more than 55% for all samples. This approach requires the laboratory determination of effect infilling material of joints on solubility of limestones and presents the application of the X- ray diffraction (XRD) and pinhole tests for the solubility measurement of the Asmari limestones in concern with the soluble rocks. The analysis of the laboratory works indicated that filling materials mostly are disperssive clays and attention must be drawn to possible washing out of clay from discontinuities under the increased water pressure because of reservoir. The increase of aperture of joints will cause an increase in the solution phenomenon and consequently the amount of discharge in joints will be increased with time. Also this paper shows that apertures smaller than about 0.5 mm are unlikely to be dangerous in most foundations in limestone.