Tunnelling Applications

Yamamoto ultra-large rock splitters have been used extensively in tunnels in many countries. Mechanical excavation with rock splitter has many advantages in tunneling works where blasting is a problem. The use of rock splitter can allow the tunneling works to progress despite tunnel alignment near existing tunnels, near sensitive buildings and structures, or in unstable rock conditions.

Splitting is done horizontally so the wedge set has to be inserted into the split hole with the help of a telescopic function. This can be either a separate attachment with telescopic function or a tailor made carrier with telescopic boom. The carrier also needs a rotator in order to control the splitting direction.

Free face is created by slot drilling, i.e. drilling a row of overlapping holes to create a continuous slot. Slot drilling can only be done by mounting a guide rod onto the jumbo boom. Please see sample drilling pattern below.

Works process includes drilling split holes, drilling free face, splitting, trimming and scaling with hydraulic breaker and then support installation. Since drilling involves both free face drilling and split hole drilling, there is a significant amount of drilling required. In a recent study, half to the complete cycle time is required for drilling, one third of the time is required for splitting, and the remainder of the cycle involves scaling, secondary breaking and support installation.

Splitting is done by starting in the bottom and working upwards. This utilizes gravity to clean off the face and improves the productivity. The same three-step process is utilized so only half of the splitter is inserted first, then ¾ and finally the full length of the wedge. Remember to grease the wedges every 5-10 split holes.