Strengthening of the Foundation Using Deep Mixing and Stone Column Techniques for Large Earth Cum Rock Fill (ECRF) Dam for an Irrigation Project

A Large Earth Cum Rock Fill, ECRF Dam is under construction in the state of Andhra Pradesh in India. The Embankment crest width of the dam is 12.5 m and base width is of approximately 136.75 m with a stepped sloping height of 27 m on both upstream/downstream sides. Plastic concrete diaphragm wall of 1.2 m thick is constructed along the longitudinal central axis to avoid seepage to depths of 96 m below the existing bed levels. The functional efficiency of plastic concrete cut-off wall is designed for the high underwater scouring and discharge velocity of river during the peak flood season. Deep single mixing (DSM) columns and stone columns are evenly arranged under the footprint of ECRF dam for smooth transition of stresses by gradually reducing stiffness moduli from Centre to Toe of Embankment. The stiffness moduli reduce gradually toward the Toe facilitating settlements within allowable limits. The paper discusses the installation of the DSM columns along the diaphragm wall and field trails carried out for establishing the desired stiffness modulus of DSM columns.