Investigation of rock mass groutability at Kaleybar Peygham-Chay dam foundation based on field data

Cement grouting is the most common methods using for improving, treatment and sealing the foundations of structures and construction sites of dam projects. In this method, through injecting the cement grout by pressure, joints and fractures of rock mass subjected to filling and as a result, the geomechanical characteristics of the rock mass improving due to integrity and reducing of permeability. The key to success in using this approach is to correctly evaluate the grout-ability of rock mass and, consequently, to determine the mixing plan and designing of grouting parameters. Peygham-Chay Reservoir Dam is an embankment dam with a clay core and a height of 46 meters from the riverbed, which is under construction in East Azerbaijan province, 15 km southwest of the Kaleybar city. The bedrock of the dam site is basalt, which is covered by alluvial deposits in the riverbed and the left abutment. The bedrock is fractured due to 3 main joints and a number of sub-joints and faults. Based on the results of Lugeon tests in the construction site along to the dam axis, in most test sections, the permeability is less than 3 Lugeon. The rock mass quality index (RQD) in the study site in 75% of sections is less than 25% and in only 1% of sections is more than 75%. Investigation of the relationship between RQD and Lugeon values shows that most sections with low to high RQD have low permeability and there is no logical relationship between these two parameters. In different RQD, the cement take is low that indicates the presence of rock mass with low to high degree of jointing with filled and/or with low aperture as well as very low continuity. The study of the relationship between the cement take and different classes of secondary permeability index (SPI) shows that there is no logical relationship between this parameters in the study site. Based on the obtained results, the rock mass forming the study site is low grout-ability.