Relation between the grout take, rock quality and permeability of radiolarite and limestone at the Roudbal Dam Site (SW Iran)

Understanding the relation between the rock geomechanical characters and its cement take is very important to estimate the cost of the dam and grout curtain constructions. Most of studied relations belong to limestone since dams are mainly located at karst terrains. A positive relation between cement grout absorption and the permeability of limestone is reported by many researchers. Roudbal Dam, with a reservoir capacity of 82 million cubic meters, is located in the Fars Province, SW Iran. The dam site is mainly consisted of radiolarite and limestone. In this study an attempt has been made to determine the relation between the cement consumption, rock quality and rock permeability of these geological units. Considering the rock quality index, limestone showed better quality than radiolarite. Based on the results of the water pressure test, limestone was more permeable than radiolarite. By analyzing the cement take values, it was detected that most of the sections with high consumption were located in the limestone. The cement take values only showed a well positive correlation with rock permeability. A correlation of 0.87 indicates a much stronger relation between cement take and permeability in limestone than correlation of 0.43 measuring the relation between these parameters in radiolarite. The results of this study showed that in sites with different lithology, estimation of cement consumption based on the results of Logan test and the rock quality index requires more accuracy and attention. By separating the data obtained from drilling in different rock units and performing calculations separately, the estimation error can be greatly reduced.