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Rietspruit, South Africa it • i The fragmentation results were Cair. From the actual prolile, It can be seen chat more throw blastng was achieved than desired, fhe pad behind the draglinc had to be rebuilt so that a conventional key cut could be dug, with the draglinc standing over the nose presplit highwall position. There n'as no benefit from throw blasting, which was ad- versel}' compensated for by the roll back required for the pad building, behind the dragline. The 90° Tie-up Based on the above experience it was dccidcd that the old paucrn and system of tic-up would be reinstituted and evaluated. The pattern was again rotated by 90° and tied so that rows would sequentially detonate at 90' to the new highvmll. In order to give thls system a (air trial it was decided to blast a section of pit, one kilometre long, using this method. PROFILE BEFORE BLAST NO. 2 SEAM FIG. 12. Section through Blast - 90° Tie-up. Although the resultine prolile was acceptable, the 'Big Gooliei reappeared and draglinc digging productivity suffered as a resul[. The 30° Tie-up A[ [his stage a section of the pit had already been drilled using the same 90° pattern. Because of the exisrencc of the sub-outcrop ~f ~No. 4 seam it was dccidcd to blas[ [his section using a 30° tie-up. W ? ORIGINAL PROFILE J L_ n ---- --f H I 39°i° N0.2 67°/ FIG. 13. Section through Blast - 30° Tie-up. Some of the Men Respo~ ~ At [his stage a plan had already been developed to apply the throw blasting phenomenon observed on the single seam operation to the double seam operation. Atie-up par- allel to the highwall was envisaged. From the section at left it can be appreciated that if the 30° tic-up gave the profile shown, the authors were conlident that even more rock could be shifted using the parallel tie-up (0°). This proved not to be the case. Parallel Tie-up A trial blast of 600m was blasted with atic-up parallel to the highwall. A sun~e~~ section of the profile is shown on the next page. E21 General Manager K. L. "Pappy" McDonald, Rietsprwt Opencast Services (Pty) Ltd.