Grouting is a method of injecting grout materials to improve geo-materials (soil and rock). In this method, the grout materials are injected into void and pore spaces in order to reduce permeability, correct faults and improve deformability of rocks. This paper examines the hydraulic features of geological formations of the left abutment of Darband Earth Dam before and after the pumping of grout materials into three boreholes of total length of 270 m. The results of permeability tests showed that the average depth of Lugeon which has been 23 m prior to injection has decreased to less than 2 m after grouting. Moreover, the findings showed a significant increase in quality indexes of rock formations after the performance of grouting.

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