01 February 2016
The activities at the lunch room of the DOZ that day were different. Workers were seen setting up a long buffet table of special food like Tumpeng (tower of rice) with complete trimmings and snacks. It’s a feast meal they are preparing. Employees from OB 4 and the entire crew of the DOZ crew were present in the lunch room because today is a historic day for the DOZ production team. It was January 20th and the day for the final undercutting of the DOZ mine.
At a separate venue, deep down in the dark underground of the DOZ, a team stands ready to conduct the final undercut blasting. In two LVs the team was driven to the Undercut DD 1J East South. Here explosives are planted in the draw bell in undercut area ready for detonation. In underground mining where the Block Caving method is practiced, undercutting is the one of the important process. Undercutting is a process to extract material at undercut level, as the initation area, that will be continued to the production level. In the undercutting process explosives are used to detach the ore deposits, a process which is called blasting. After blasting, the rock material will fall down naturally following gravitation and its weight, and then will be extracted by haul trucks for the next process to begin.
The DOZ mine is now 15 years old. Its first undercutting took place in November 2000 with undercutting area 360.000 m square with total of 12.000 rings. History tells us that since the first production, not one LTA ever occurred in the DOZ mine.
An achievement that genuinely deserves two thumbs up considering the mine is heavily exposed to fallen material and stain burst caused by level of abutment stress. After the last undercutting, production will resume as usual in the DOZ until the end of DOZ mine life.
Ferry Widiyanto, Gen. Supt. DOZ & DMLZ Engineering said, “The production output in the DOZ will continue until 2021. The DOZ production team is planning to increase production in 2016, 2017 and 2018 and lower it in 2019 until the mine closes in 2021. Daily output at the moment is 60 thousand tons and can be increased in accordance with planning.
What was unique about the last undercutting was the presence of the mine’s trailblazers at this historic moment. Herry Siswanto, is one of them. He was literally involved in the birth of the DOZ mine. “I’m very moved and very proud of the DOZ, which is a master creation by my fellow countrymen. I feel honored being given the opportunity to be involved in this project from the beginning to the end,” Siswanto is retired since 2013 but has rejoined the team as technical advisor and consultant in developing new underground mines and to transfer knowledge to junior engineers directly involved in the underground.
As a message to the new generation of engineers he said never become bored with learning new technology that can be applied to the underground.“This is a megaproject, the pride of the future. We should boost our skills and competence to make this a project of excellence for the future,” he said.
Exactly at 12.30PM the last undercut blasting at the DOZ took off. It marked the end of a phase at the DOZ, a gift from us to Indonesia. (Miko Sularso)