Blasting Materi

BLASTING 1) Free face make the rock moves freely because created new free space. Rock movement direction tends to slide into the free face. Therefore, if there is only have one free face, so the rock tend to fly to upward or called as flying rock. 2) Burden is the distance between free face with shot hole. If the free face too closes with borehole, it will be happened flying rock, because the energy is too huge. If the free face too far from borehole, so the blasting result is not good enough. 3) Stemming is the column in the borehole that filled by non-explosive substances (stones or cutting from borehole). The size of stemming column determines the result of blasting. If stemming column too short, then vertical energy and explosive energy that will be happened too huge, therefore will create flying rock and indicated with concave dome at material blasting. 4) In blasting method, stiffness ratio that proposed not exceed then 1, 25. Stiffness ratio is a comparation between the size of “jenjang (bench)” with the size of burden. Its mean size of “jenjang” have to bigger ¼ time than burden size in order to make good blasting results. 5) In delay installation, we have to concern about the precision. If we have long burden then installed fast delay, then it will be occurred heavy load for next process blasting, because the first blasting isn’t finish yet then continued with next blasting, because not create free face yet.

Blasting Theory Rock rupturing process at blasting From initiation

point (titik pembakaran), explosive material break shot hole wall, this

happened because of huge pressure around blasting area.

Compressive stress spread to all direction with the equal velocity and sonic wave velocity, when this compressive stress pass through free face and bounce back, therefore create tension force when rock tension force exceeded and the rock will rupture. When produced fracture because of rock rupture, gas expansion from blasting material pull the rock to all direction. The quality of borehole can be looked from:  Sequence of boreholes  Direction deviation and the angle of bore  Depth and purity of borehole There are 2 drilling pattern; Rectangular pattern Staggered pattern

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Free Face

Pola pemboran square, pola peledakan VCut

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Delay relay connector (DRC)

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Free face If burden too tight, then the rock will not be deformed perfectly and explosive energy throwed as ground vibration. Bila “Burden” terlalu tebal maka tidak terjadi deformasi batuan yang sempurna dan pada keadaan ini energi bahan peledak akan terbuang berupa getaran (ground vibration). Sebaliknya, bila “Burden” terlalu tipis maka sebagian besar energi bahan peledak akan terbuang sebagai suara (Noise) dan air blast. Untuk itu harus dicari / ditentukan jarak burden sedemikian rupa sehingga energi bahan peledak terpakai untuk menghancurkan (men “deformasi”) batuan.