ABSTRACT
Example 1-Tunnel in open construction During the excavation of a 12 m deep tunnel (open trench operation) located on the western periphery of the German city of Bautzen, in Saxony, 83 blasts had to be performed in a highly populated area. The rock was granodiorite which is a notoriously difficult rock with very poor blastability. The nearest residential and business buildings were located in close proximity of 3,2-5,6 meters from the detonation site. The excavation work was obstructed and impeded by a gas main at 3 m distance and also by three steel bridges. Considering this complex situation the blast operation was designed on the basis of the new advanced blasting theory. The first part of the blast operation consisted of about 40 supersonic split blasts, each of them had an
explosive charge of 7,5 bis 11,5 kg PETN. The second phase began at a depth of 5-6 m below street level. Due to the larger distance from the buildings and in order to save drill meterage this phase was designed a fragmentation blast. The charge per blasthole was 4 bis 8 kg gelatinous explosive.
