Robot does the dangerous work

New robot technology saves time and improves blasting safety.

By Jan Helstad
The need to automate blasting operations, save time and raise safety standards is what underlies the development of a new robot explosives charger. Plans exist to load explosives in holes at the same time as new holes are being drilled only a few metres away. In order to make blasting operations safer and reduce the danger of being hit by falling stones, stricter rules are about to be introduced that will limit the number of people allowed at any time at the end of the tunnel.
Explosives manufacturer Dyno, the Selmer construction company and the Public Roads Administration have been collaborating on a project with Bever Control in Lier, with financial support from the Research Council of Norway. SINTEF Electronics and Cybernetics was brought in to develop a vision system that would help the robot to find its way to the drill-hole.

More automation at the rock-face
Many aspects of tunnel boring are already automated. Blasting holes are drilled by a computer-controlled drill-rig that drives up to the rock-face, orients itself with the aid of a laser beam transmitted from a known position and drills the holes according to a pattern calculated on the basis of the condition of the bedrock and the tunnel profile that is wanted. Everything is monitored by a single operator from a well-protected cabin on the rig.
After drilling is finished, the detonators and fuses are pushed into the holes by hand. Most large construction sites now use an explosive slurry that is mixed on the spot just before it is pumped into the drill-holes. The explosive, which has the consistency of cream, is not active until it has been mixed, which makes it extra safe.

Positioning via image processing

A tunnelling robot at work. In the future, it will load drill-holes with explosives as well as drilling the holes themselves. The new method will improve safety levels for tunnel workers. Photo: Berver Control

SINTEF research scientist Trine Kirkhus says that the job of helping the robot to find the hole has been solved by replacing one of the rig’s four drilling arms with a charging arm, which has been provided with “sight”.
– We use a video camera at the charging nozzle, she explains.
– The drilling program, which after all “knows” where it has been drilling, provides the first rough orientation, which is enough to put the hole in the camera’s field of view. This image is then processed by computer so that the drill-hole can be distinguished from other dark areas in the picture. Once the charging nozzle is in position it is inserted a little way into the hole. The flexible hose that fills the hole with explosive first pushes the detonator and fuse all the way to the bottom of the whole, where the explosive is then squeezed out behind the detonator. The hose is withdrawn as the hole fills up, and when filling is completed, the fuse is hanging out of the hole. When all the holes have been filled the drilling rig pulls back, the fuses are connected and the charges can be detonated.

100 bangs in six seconds
– It is important that all the explosions do not take place simultaneously, but rather at intervals of a few hundredths of a second, says Thorvald Wetlesen, managing director of Bever Control. – It takes about six seconds to fire off 100 holes. This is to give the loosened material somewhere to go. Each individual detonator must therefore be set off with a specific delay and must be placed in the correct hole to give us the correct explosion symmetry. We are cooperating with a rig manufacturer, Andersens Mekaniske Verksteder in Arendal, who have installed the first prototype on a rig so that we can start field trials.
The technique will probably used in both tunnelling and ordinary mining operations. Even so, Wetlesen believes that there is still a good way to go to the complete automation of blasting.

Contact at SINTEF: Trine Kirkhus
Tel: +47 22 06 79 67
Email: Trine.Kirkhus@ecy.sintef.no