Karst Studies and Assessment of Groutability of Rock Foundation in Ekbatan Dam (Heightening Pattern)

Ekbatan dam is a buttress gravity concrete dam. This dam is performed on Yalfan River in 5 km from south-east part of Hamedan, Iran. The purpose of dam is providing the drinking water of Hamedan city. It should be noted that more than 50% of dam capacity is filled by sediments. For this reason and in order to provide the drinking water of Hamedan city, it was decided to increase the height of old dam. The old dam was performed on the schisty rocks. Due to the heightening of dam and increasing of dam foundation, a main part of dam foundation is located on the karstic limestones. This caused to be worry about the bearing capacity, settlement and seepage problems in the new dam site. In this research, both labratoray and filed investigations have been carried out. Results show that rock mass properties are in medium category and they show potential of solubility. In this site, orientation of the main joint set is as same as Zagros zone orientation, which plays an initial role in distribution of karstic conduits. Recognition of karstic zones has been carried out using boreholes and water pressure tests data. Results show that karstic zones in the right abutment and also central part of the dam are located in the surface parts and maximum in 30m depths. Whereas, concentration of karstic zone in left abutment has been develop in 55-80 m depths. Because of dam heightening and in order to increase the bearing capacity of dam foundation and prevent the seepage problems, cut off design and grouting have been carried out. Consequently, their results have been analyzed.