A system for blasting a geological formation (g) to form therein a tunnel having a perimeter wall enclosing an interior space, the system comprising: a series of perimeter boreholes (15, 16, 17) disposed in such geological formation (g) in a pattern corresponding to such perimeter wall, with explosive charges disposed in respective ones of the perimeter boreholes (15, 16, 17); a series of interior boreholes (1-8, 10-14) disposed in such geological formation (g) interiorly of the perimeter boreholes (15, 16, 17), with explosive charges disposed in respective ones of the interior boreholes (1-8, 10-14); electronic delay perimeter detonators having fuses are disposed in respective ones of the perimeter boreholes (15, 16, 17) in signal-transfer communication with the explosive charges contained in the associated perimeter boreholes (15, 16, 17), and pyrotechnic delay interior detonators having fuses are disposed in respective ones of the interior boreholes (1-8, 10-14) in signal-transfer communication with the explosive charges contained in the associated interior boreholes (1-8, 10-14); the fuses of both the perimeter detonators and the interior detonators being connected in signal-transfer communication with a non-electric trunkline, whereby to initiate both the perimeter detonators and the interior detonators by an initiation signal transmitted via the trunkline, characterized in that - the fuses of the electronic delay perimeter detonators are shock tube fuses, - the fuses of the pyrotechnic delay interior detonators are shock tube fuses, - the system comprises a single non-electric trunkline to which the shock tube fuses of the electronic delay detonators and of the pyrotechnic delay detonators are connected. a series of perimeter boreholes (15, 16, 17) disposed in such geological formation (g) in a pattern corresponding to such perimeter wall, with explosive charges disposed in respective ones of the perimeter boreholes (15, 16, 17); a series of interior boreholes (1-8, 10-14) disposed in such geological formation (g) interiorly of the perimeter boreholes (15, 16, 17), with explosive charges disposed in respective ones of the interior boreholes (1-8, 10-14); electronic delay perimeter detonators having fuses are disposed in respective ones of the perimeter boreholes (15, 16, 17) in signal-transfer communication with the explosive charges contained in the associated perimeter boreholes (15, 16, 17), and pyrotechnic delay interior detonators having fuses are disposed in respective ones of the interior boreholes (1-8, 10-14) in signal-transfer communication with the explosive charges contained in the associated interior boreholes (1-8, 10-14); the fuses of both the perimeter detonators and the interior detonators being connected in signal-transfer communication with a non-electric trunkline, whereby to initiate both the perimeter detonators and the interior detonators by an initiation signal transmitted via the trunkline, - the fuses of the electronic delay perimeter detonators are shock tube fuses, - the fuses of the pyrotechnic delay interior detonators are shock tube fuses, - the system comprises a single non-electric trunkline to which the shock tube fuses of the electronic delay detonators and of the pyrotechnic delay detonators are connected.