During excavation of tunnels by drilling and blast method, the rock around the tunnel bore gets shattered to a certain depth. This will depend upon type of blasting as well as type ofsurrounding rock. Consolidation grouting is to consolidate the shattered rock by filling up the joints and discontinuities in the rock which got opened out during conventional blasting. Consolidation grouting improves the rock quality which will increase resistance of the rock for internal water pressure. Normally, it isbeing carried out from holes left in steel lining ferrules from inside the tunnel. THDCIL has adopted innovative Criss-Cross grouting around vertical penstocks of Koteshwar HE Project due to time and space constraint. Grouting around vertical penstocksfrom inside was creating problem to activities of Power House and Power intake due to space constraint. THDCIL had been working under a very tight commissioning schedule due to which it was planned that all the balance activities of Power House, Power intake and vertical penstocks are done as parallel activities.
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