Grout curtain effect on downstream groundwater geochemistry at Daryan earth dam of Kermanshah

A grout curtain is constructed beneath the dam foundation to control water seepage. Cement is used to execute the grout curtain and to extend until it reaches impermeable bedrock. Grout curtain will mostly reach groundwater, too. The reaction between cement and water caused the cement compound to enter groundwater and changes its quality. The extent of change and its continuity is important so that it needs to be studied and investigated over time. In this research, the change of water quality has been studied by comparison of water test analysis during 4 years. For this purpose, four phases of water samples including site springs samples before any disturbance (first phase, 1392), after cement grout and before impoundment (second phase,1394), and also two phases samples after impoundment (third phase,1395 and fourth phase,1396) with one-year interval were examined. Samples of the second, third and fourth phases were taken from observation wells which are located downstream of the grout curtain. Therefore, it is expected to see the effects of cement entry in the groundwater flow through the curtain to the observation wells. In this study after categorizing the achieved data, using SURFER and GIS software, different parameters were interpolated in different periods and compared by the production of zoned maps, and the degree of variation of different elements was investigated. Diagrams and maps show that pH, SiO2, Na, K, Fe, CaCO3, SO4 and EC have been significantly changed which indicates that cement compounds have been entered into the groundwater and have decreased the water quality.