Challenges in flattening of hill by blasting for construction of international airport at Navi Mumbai, India

Excavation of rock by blasting in densely populated area is a challenging work in terms of its adverse effect. Blasting operation involves the interactions of blast design parameters and rock properties with explosives parameters. Optimization of blast design parameters for civil construction site plays a vital role to control the adverse effects of blasting. This paper deals with optimization of blast design parameters for flattening and Demolition of cliffs of Ulwe Hill by controlled blasting techniques which was surrounded by densely populated area. More than 5000 blasts including almost 50 challenging cliff blasts were conducted at different locations of the Navi Mumbai International Airport (NMIA) construction site in order to flatten the Ulwe hill height from 92 mRL to 8 mRL. Blast designs were developed and executed in order to achieve the desired fragmentation level i.e. 300 mm to 700 mm for preparation of stable runway foundation with minimum blast induced ground vibration level. The excavation has been completed about 60 % of the total volume of rock till August 2019. The Ulwe hill was surrounded by 10 villages and most of the villages have been shifted to another locality. However, controlled blasting operations are being carried out nearby two villages and High Tension line which are the major issue now a days. The study involved designing, planning and supervision of the total drilling and blasting operations, suggestions/modifications in blast design parameters, monitoring of blast-induced ground vibrations, noise/air overpressure, quality test of explosives and its accessories in order to process to achieve the desired objectives of the project. Rock fragmentation analyses were carried out for each blast using photo-analysis system and subsequently blast designs were modified to get desired fragment size for land development work. The sequence of detonation, rock movement and stemming ejection during the trial blasts were recorded in each blast