Excavation of Centre Gullet, Widening and Benching of Underground Machine Hall of Teesta (Stage V) Hydroelectric Project, East Sikkim

摘要

This paper presents the blast design, supports and sequence of excavation for centre gullet, widening operations of underground machine hall to its full -width and depth (benching). The average progress, pull obtained per round of blast, was 90% and the hole blast impressions observed after blast were more than 80% of the actual drilled length. The progress of centre gullet and side widening achieved were 40 m per month and 45 m per month, respectively. The average benching progress achieved was 12 000m~3 per month and maximum benching progress achieved was 18 000m~3 in a month. The recorded blast induced vibrations were within safe limits. The performance of blast and post-blast observations indicate that the drilling and the charging patterns followed for the aforesaid underground excavations were safe and efficient.