Change in Methodology in Construction of Plastic Concrete Cut-Off Wall Adapted in Kishanganga HE Project

In the Himalaya, rivers have carved out deeply incised valleys where construction of dams is a challenge as a number of sites have thick overburden in the river bed. At Kishanganga HEP in J&K, a 37m high concrete face rock fill dam with 33m deep cut-off wall was planned and efficaciously executed. Construction of the project began in 2009 and all the three units (3 × 110 MW) were successfully commissioned in March 2018.

One of the key aspects of the project was the construction of a 134m long, 1m wide plastic concrete cut-off wall (diaphragm wall) below the dam upto the maximum depth of 33m in overburden. Based upon the previous experience gained from different projects, significant amount of desk studies were taken up during the design stage to develop a scope of work for the possibility of construction of cut-off wall either through mechanical means like trench cutter or drill-blast method.

Unlike the prevailing mechanical method like trench cutters, the cut-off wall in Kishanganga HEP was executed by drill and blast & hydraulic grab picking method due to the presence of high strength boulders and other reasons. Highly specialized methodologies as well as equipment deployed have also been discussed.