KAJIAN TEKNIS GEOMETRI PENGEBORAN DAN PELEDAKAN OVERBURDEN UNTUK MENENTUKAN UKURAN FRAGMEN BATUAN HASIL PELEDAKAN YANG SESUAI DI PT. BUMA JOB SITE PT. KIDECO JAYA AGUNG KALIMANTAN TIMUR

PT. Bukit Makmur Mandiri Utama is the one of contractor which producing coal as a source energy, whereabout the located is PT. Kideco Jaya Agung in Batukajang subdistrict, East Kalimantan Province. PT. Bukit Makmur Mandiri Utama split the coal minning areas, they are Pit A and Pit M which use strip mine methode. In mining operation of overburden PT. BUMA use non electric blasting methode. At this time it use blasting and drilling methode and the burden 7 m, spacing 8 m, heigh 8,5 m, powder factor 0,25 kg/m3, stemming 4,3 m, subdrilling 0,5 m, powder charge 4,2 m, and hole diameter 200 mm. With that geometry it will get the actual fragmentaion with boulder ≥75 cm is 21,59 % from blasting volume production, and while the company production target is getting boulder less than 15 % and the maximum limit from powder factor is 0,3 kg/m3, so that need improvement to get boulder less than 15%. After it did calculation in theoretically so it get boulder ≥75 cm is 12,9 % with advice to change the blasting geometry. Those are burden 5,5 m, spacing 8,5 m, heigh 9,1 m, powder 0,3 kg/m3, stemming 4,9 m, subdrilling 1,1 m, powder charge 4,2 m, and hole diameter is 200 mm. This geometry is according to company target that boulder less than 15 % and maximum limit of powder factor is 0,3 kg/m3. Keyword : Blast and drill, Geometry , fragmentatio