ABSTRACT
The tes t column s wer e burie d 400m m i n th e ground . Th e specifie d design strengt h of concret e was 210Kgf/cm 2 an d the strength for 28 days later indicated 351Kgf/cm2 in the test piece.
2.2 Blasting Methods The fou r kind s o f blastin g experiment s whic h ha d n o cove r material s were carrie d out . The blastin g condition s of experiments were shown i n Table 1. The charge of explosives was defined as follows;
L = C • A
where L i s amoun t o f explosive s i n kilogram , C i s th e co - efficient o f blastin g an d A i s th e cros s sectio n o f a specimen . I f the charg e poin t i s biased , A i s t o b e calculate d a s a n are a o f a square wit h a sid e twic e a s much a s th e minimu m resistin g length . The explosives use d i n th e experiment s wer e No. 3 Kir i dynamite ( 35m m i n diameter, 200g) and initiate d b y No.6 electric detonators. The diameter of drillin g hol e wa s 37mm . Th e fou r kind s o f experiment s ar e shown i n Fig.l ~ 4 .
