Challenges in Engineering of Pare Dam on Weak Foundation

Bedrock of the 63 m high Pare concrete gravity dam is low strength, friable, fine to medium grained sandstone with occasional intercalations of claystone, shale and pebbles. Test results in the dam area indicated that the rock mass exhibited very low values of the deformation modulus (0.45 GPa) and the allowable bearing pressure (2.6 MPa). Water percolation and groutability tests also indicated generally very low permeability and low grout intake, although erratic at locations. Major concerns in the design of the dam in such ground conditions were to prevent or minimize undue settlement including differential displacements of the dam blocks, minimize erosion of the dam foundation material during seepage and ensure efficient sealing, grouting and drainage arrangement. Design of the dam had to be adapted as the construction progressed. This paper discusses the challenges involved in engineering of Pare dam on a weak foundation.