Efficacy of Grouting in Head Race Tunnel

Contact grouting is done to fill the cavities/voids between concrete and rock mass on account of shrinkage of concrete and uneven over breaks. Consolidation grouting is done to strengthen the surrounding rock mass by filling up the open joints, fissures, cracks etc. This paper deals with quality control assurance of the grouting operations (contact/consolidation) and permeability tests carried out in head race tunnel (HRT) of Tala Hydroelectric Project in Bhutan. Efficacy of grouting was determined by conducting permeability tests before and after consolidation grouting. Proper grouting of surrounding rock mass around the opening helps in monolithic behaviour of the rock mass. The quality assurance during grouting was ensured by checking the properties of all materials being used and by conducting permeability tests in pre/post grouting stage.