Since mobilization in Apr 2020，raise boring team at Dong’An Gold Mine strove forward despite of the impact by COVID-19, and successfully completed the breakthrough of three short raises by 31 May 2020, laying a solid foundation for follow-up works.
Located in Xunke County, Heihe City, Heilongjiang Province, the scope of work for raise boring division at Dong’An Gold Mine mainly includes pilot hole drilling and reaming work for vent raise, pipe & cable raises and ore pass.
The required labor was mobilized on 25 April, but the first hole was not drilled until 4 of May for the outside temperature was still low in April which made curing process of rather slow.
The first borehole was for backfill with a depth of 40m and diameter of 0.3m. A “low pressure, high speed” mode was applied to drill pilot hole for rectifying deviation. It took only 4 days to complete pilot hole, reaming and stripping were completed on 13 of May.
The second filling raise was designed with 60m depth, and diameter of 0.3m. As its position was close to the slope, drilling process was interrupted due to severe water inflow from fault, grouting treatment was applied immediately and cured for one day before resuming drilling of pilot hole. Pilot hole of the second raise was completed on 22 May, with reaming and stripping work completed on 24 May.
On 25 May, raise boring machine was relocated to slot raise at -185mL for the construction of the third raise, which was 40m deep with diameter of 1.4m. At first, drilling of pilot hole was slightly deviated for it was in granite and ore zone. But the deviation is rectified through changing of working method, and it only took 5 days to complete pilot hole drilling with reaming and stripping work finished on 31 May.
The completion of these three raises largely facilitates subsequent material transportation and stoping work.
