Calculation of the changes of rock joint apertures affected by dissolution through experimental and theoretical methods (A case study: Gypsites of Chamshir dam reservoir)

In the karstic areas، detailed studies of phenomena such as seepage of water from hydraulic structures and land subsidence in the residential and quarry areas is of higher importance. In this study، the dissolution rate constant of gypsite samples of Gachsaran Formation، obtained from the Chamshir dam reservoir، were measured equal to 0. 24×10-3 cm/sec. Then، the changes of amounts of joint apertures using theoretical and experimental (by changes of joint water flowing and direct measurement) methods were calculated. The results showed that the predicted aperture for joints calculated through theoretical method is less consistent with the measured value of the changes of joint water flowing; while the value measured by direct method (measured using a caliper) compliance is higher. Also based on research findings، if gypsites of the dam reservoir are exposed to the water flow، the amount of aperture of a joint with 0. 5 cm initial opening will increase to 10 cm after about 278 days. This increase in joint aperture compared with the useful life of the dam draws for special attention to water tightening of dam reservoir.