Newpac Rapid Road Trial

UGM in conjunction with Yuleba Minerals have been developing a cementitious road repair product call “Rapid Road”. The aim of the product is to allow the rapid and efficient repair of mine roadways. Rapid Road is a dry mix early set high strength concrete blend.

Background

Newpac Colliery was seen as an ideal site to trial the material. Newpac Colliery has a varying floor thickness and in places floor breakthrough has caused some large bog holes.

Trial

The trial was carried out in the long wall 2 main gate drive heading. A bog hole as shown in figure 1.1 was selected for the trial.

Friday 4/5/07 The bog hole was mucked out to remove as many silts and clay like material as was possible. Air pumps were set in the bog hole to remove the water in preparation for the installation of the rapid road.

Saturday 5/5/07 The water level in the bog hole had not changed and silts were again present in the water. Whilst these were far from ideal conditions to install the rapid road it was decided to proceed with the trial. The original plan had been to open each bulka bag and rake material on the floor while wetting the material to form a slab ranging from 150mm to 250mm thick. Surface trials @25 Deg C had given a working time of between 5 and 10 minutes.

The revised plan was to place the material into the water starting at one end of the bog hole and work back. It was decided to start at a water depth of approximately 200mm and work towards the centre of the bog hole.

The down side of this method was that we had to add enough material to fill the area until we had reached the top of the water. This was the only way we could ensure we had added enough material into the water, our concern being the muddy silts in the bog hole would adversely affect the final strength of rapid road.

The 16 bags (16 T) of material were stored in an area just out bye of the bog hole. A crew of 4 people including the Eimco operator took approximately 3 ½ hours to install the 16 bags of material. The crew started by bringing one bag at a time and then changed to bringing the bags on a trailer and hanging the bags from roof bolts allowing the crew to split them as they worked there way along the heading (see fig 1.3).

The rapid road surface trials showed the material to be workable for 5-10 minutes. During the installation at Newpac the rapid road seemed to remain workable for up to an hour figure 1.5(left) show the material after approximately 30 minutes while figure 1.5(right) is after approximately 90 minutes.Originally 24T of rapid road had been delivered to site of this 8T was mistakenly used leaving 16T. While 16T would have been enough to fill the area if it had been pump, the 16T filled an area approximately 5 meters wide by 8.5 meters long and a further 30 bags (30T) would be needed to fill the remaining bog hole.

Tuesday 8/5/07 the site was inspected (figures6) to see how well the rapid road material had held up. On inspection the rapid road was intact and while the area had been subject to some vehicle traffic the rake marks were still clearly evident in the surface of the rapid road. This would indicate that although the rapid road was used in very adverse conditions and that silts and clays in the water would have degraded its ultimate strength the rapid road had still obtained a reasonable strength.

The testing confirmed that the current rapid road mix provides enough working time to place the material. The testing conditions were not ideal but did show that the rapid road formulation even when subject to significant silt contamination provides adequate strength.

Conclusion

While installing rapid road directly into water worked, to gauge the mix the rapid road was mixed until it reached the surface of the water and it would be difficult to mix it to a level under the waters surface. This meant that even though we were originally going to lay a slab up to 250mm thick we ended up with a slab in places 500mm thick. Thus considerable more material is required and roof height was lost in the process.

In future situations where the water cant be removed the crew and offsite engineering staff would propose first filling the area with crushed rock or iron stone up to a level approximately 200mm bellow the desired finished surface then (providing the water level is bellow the desired floor level) apply the rapid road in accordance with the original installation guide to provide a finished slab approximately 200mm thick.

Yuleba is located in Southern Queensland (near Roma, Surat, Miles and Chinchilla) and services mines in NSW and QLDKerry GroverGreg Moorewww.yulebaminerals.com.au