Estimation of the grout take using empirical relationships (case study: Bakhtiari dam site)

Seepage in the foundation and abutments of a dam can lead to wasting of the stored water in the reservoir, erosion of the foundation materials and increasing the uplift pressure. It can endanger the long term stability of the dam. Cement grouting is one of the seepage control methods which is generally implemented according to the Lugeon test results. In this study, the grout volume has been examined against Q-value, Lugeon number, SPI (Secondary permeability index) value and joint apertures in the Bakhtiari dam site. In Bakhtiari dam site, the left and the right abutment trial grouting boreholes were drilled up to the final depth of 60 and 100 m, respectively. Limestone of the Sarvak Formation is the dominant rock type in the site. The Q-system parameters have been evaluated by eye-examination of rock cores, the Lugeon numbers and SPI values have been deduced from the water pressure tests and the joint apertures have been calculated based on the permeability of rock mass and the joints spacing. The Q-value, the Lugeon number, the SPI value and the joint aperture have been compared with measured cement take and grout take in the trial grouting boreholes. A general correlation exists, especially when the mentioned parameters have been compared with normalized grout take. Against these general agreements the coefficients of determination for the fitted relations are low or moderate, and it seems that more research has been needed to assessing a reliable predictive relation for the grout and cement takes.