APPGENCO's Srisailam left bank hydro project in Central India, comprises six reversible units of 150MW capacity (Figure 1). The draft tube vents of five out of the six units were sealed with concrete plugs (Figure 2a,b) to stop sudden ingress of water from the surge gate side. Each unit was blocked with two plugs. These plugs needed to be removed, in a phased programme, before commissioning the units. Dimensions of the plugs are indicated in Figure 3. Other methods, such as breakage by use of non-explosive swelling powder and manual chipping had proved unproductive. Concrete cutting was considered too costly and would pose difficult situations owing to lack of flexibility at the site and a restricted approach via a manhole. Keeping in view the time and financial constraints the removal of the plugs with controlled blasting was planned. In total 250m~3 of partially reinforced concrete had to be removed from each unit.
展开▼
