A test laboratory for high-rise lifts to be built in a Finnish limestone mine

2017 Mar 15

Lift manufacturer Kone Oyj is conducting excavation work at the Tytyri limestone mine to construct a test laboratory. Tytyri limestone mine is located in Lohja in the southern parts of Finland. The test shaft is being excavated for testing lifts intended for medium and high-rise buildings. The side dimensions of the shaft are 10 x 10 meters, and it extends from the ground level to a depth of over 100 meters. The total duration of the project is from July 2014 to October 2015, during which time an approximate total of 34,000 meters will be drilled. The contractor for the project is Lemminkäinen Infra Oy.

At the outset of the work, a pilot hole of approximately two meters in diameter was excavated in an upward direction using the Alimak method. In this method, the raise climber runs along a toothed rail installed in the wall of the shaft. The lift features a covered working platform, and the drilling is carried out with a manually operated machine.

Once the pilot hole was complete, the expansion of the shaft was initiated in a top-down direction. Two drill rigs are used, one of which is the FlexiROC T20 R equipped with a COP 1140 rock drill. A total of 19 645 millimeter holes will be drilled in a single blasthole pattern, and bolt holes will also be drilled into the wall. The rig uses SR 28 drill rods. After completing the blasthole pattern the drill rigs will be lifted up. Blasting will take place and after cleaning the shaft from rocks, the drill rigs will be lowered into the shaft again for the next round.

Drilling one round takes about 16 hours, and there are two, three, or sometimes even four blasts a week. The shaft sinking work proceeds about three meters at a time. Because there is a tunnel underneath the shaft, the very bottom of the shaft cannot be reach by the drill rigs as they run the risk of collapsing into the tunnel. Instead, the final section will be drilled from the bottom up using long hole drill rigs.

FlexiROC T20 R is the second smallest member of the Atlas Copco family of drill rigs. It is also available with a short feed which is particularly well suited to drilling in narrow and cramped spaces. The rig has a hole range of 38–64 mm and features full remote control.

Worksite conditions

The rock drilled in Lohja is marble and light, sparsely fractured granite. According to Site Manager Kari Lehto, it is easy to drill – sometimes hard, sometimes soft – and has not caused any problems for the drillers.

What about water? Has this been a problem at the site?

“The water is mainly rainwater and hasn’t caused any issues. Once the snow melted, our boots weren’t always long enough for the deepest pools, which was a slight setback in terms of work comfort. Still, snowfall over the past winter was relatively low, so the meltwater drained away quite rapidly,” Lehto recounts.

The FlexiROC T20 R drill rig has worked well, and no problems have emerged aside from minor hose breakages and electrical issues. Atlas Copco’s service technician, Tero Lång, performed the 500-hour maintenance on the rig, but no other measures were required. The FlexiROC rig has proved its worth, particularly in the horizontal drilling of bolt holes. Driller Tuomo Ylikatila says he found the rig “surprisingly easy and pleasant” to use. At the beginning of the project, operator training was arranged at the worksite by Atlas Copco Stonetec’s product expert Fulvio Castagno.

The worksite is accessed by a cage that is raised and lowered by a crane – an exciting experience to the average visitor. But how do the drillers feel about working in the shaft?

“They are enthusiastic and motivated, they like the work they do.” Lehto says.

Epiroc operated under the trademark “Atlas Copco” prior to January 1, 2018.