PACKER TEST AND CURTAIN GROUTING IN FOUNDATION OF DAM

Abstract

Curtain grouting is an important component for the Foundation treatment of Dam and other hydraulic structure. The main purpose of curtain grouting is to form a zone of low permeability up to a design depth on the upstream side of the dam. Before performing the curtain grouting, the Packer test is performed to know whether grouting is necessary or not, and if it is necessary then at what pressure grouting is to be carried out. The grouting and the drainage pipe install in downstream side controls the uplift pressure and piping which are main cause of failure of concrete gravity dam. This thesis deals with performing packer test to know the permeability of rock mass and providing grout curtain to Pare Dam foundation from Block no. 03,04,05,06,07 and 10 in different-2 bore hole and at different-2 elevation level which was provided by design and drawing contractor SNC.LAVALIN and sanctioned by NEEPCO.

The Lugeon value generally observed during packer test lies less than 1.0 but sometimes it goes beyond15.00. The Lugeon value less than1.0 represent that the Condition of Rock Mass Discontinuities is very tight. The rock mass below the foundation is mainly consisting of sand stone. The single line grout curtain has been effectively performed below the foundation, despite very poor strata having maximum pre – grout permeability up to 54 Lugeon. Each bore hole is consisting of 76 mm in diameter and depth varies from 28 m to 43m.