A successful test that proved that difficult drilling conditions were not a problem and that
significant time savings could be made by using Wassara’s WICS system.
After an increase in the height of the tailings dam at Boliden Aitik, the dam wall needed to be fitted with observation wells. This in order to control and secure the stability of the dam. Since the dam site consisted of large boulders the drilling conditions were hard.
Due to the difficult formation it was time consuming to install pipes and filters for deep observation wells on site. During an earlier stage observation wells had already been installed, then with a total working time of 2 days per 30-meter pipe well. These depths also meant that a subcontractor, normally a well-driller, had to be hired as consulting firms only had smaller geotechnical rigs available and a bigger one was required.
WICS - the problem solver
Boliden Aitik was looking for a new and more efficient way to drill instrumentation wells. In collaboration with Wassara, Ramböll and Geofound, the patented dam instrumentation system WICS was tested. The WICS system was used to quickly install two instrumentation wells with a small GM75 geotechnical rig, without taking in an additional subcontractor.
The drilling in the embankment was done through support filling, that consisted of very large boulders. Under no circumstances could the dam wall be pressurized. Nor could the risk of flushing out materials during drilling be taken.
Great time savings
In total, two instrumentation wells were installed down to depth of 31 and 26,5 meters, respectively. These were installed to coincide for immediate connection to the previously installed instrumentation wells.
The total time required for the installation, including establishment and relocation between the holes, was only 3.5 hours. This should be compared to the two previous installations that had taken a total of 4 days to complete. In pure time-savings terms, this meant that the installation was 8 times faster than with traditional equipment! An added benefit of this method is the opportunity to use the same geotechnical rig for exploration while drilling down.
To the left, an earlier installed instrumentation well, with traditional OD-drilling. To the right, the WICS installation.
Drilling water was taken from a bowser truck equipped with an on-board pump. No return flow of water came to surface, so no return water handling was called for. During the installation of hole no. 2 (26.5 m), about 900 litres of water were used.
The GM75 rig drilling with the WICS system.
Minimal impact on the surrounding at earlier excavation of a WICS installation.