Assessment of Curtain Grouting Used in the Foundation Treatment at Dam Complex of Upper AtbaraRiver

Abstract

Curtain Grouting (CG) is aprocedure mainly used to control water seepage in dams by sealing off fissures or joints in bedrock, granular soil pockets and minor cavities; hence CG can be considered as foundation improvement method. This process involves grouting a line, or several lines, of holes in sequence along the water cut-off zone and requires specialized instrumentation to monitor grout pressure and flow parameters.Geological and geotechnical properties of the rock and soil to be grouted are important parameters influencing the design of the curtain grouting. The Dams Implementation Unit (DIU) at the Ministry of Water Resources, Irrigation and Electricity (MWRIE) was responsible for the implementation of Dam Complex of Upper Atbara Project (DCUAP). This dam complex comprises two dams namely: Rumela Dam and Burdana Dam on Upper Atbara and Setit Rivers in the eastern Sudan. The purpose of this study is to review and assess the design of the grout curtain which was used to treat the foundation properties at the different sections along the dam axis. In this study, general description of curtain grouting design in DCUAP is made. The materials used in grouting and the grouting pressures values are presented. The general procedure, equipment used and methodology of curtain grouting construction in the DCUAP are presented, as well as the tests used in the quality control of grouting works. Curtain grouting is applied in 14 sections along the Rumela and Burdana dams. In this study 300 meters section at Right Bank of Burdana dam (Chainage 1+600 to 1+900) has been selected for assessment. The grouting works in the selected section had been studied and the grout results had been analyzed to determine the quality of grouting worksregarding achievement the desired goals in terms of reducing permeability in the foundation of the dams. As well as quantifying the amount of the solid matters of curtain grouting used in the grouting process in that section and then comparing it with the quantities indicated in the project's bill of quantities. The analysis of the selected section data concluded that the permeability was improved by about 85% from the original value. The estimated amount of grout given solid material in the design documents (Bill of Quantities) is found to be much higher compared to the real grout absorption in the site which was less than the contract amount by more than 18 times. This result clarifies the importance of post project assessment studies, like this study, in the properestimation of CG materialtypes and quantities for future damprojects.