Challenging drilling in Brinzauls
Challenging drilling in Brinzauls

Challenging drilling in Brinzauls

Brienz/Brinzauls in the canton of Grisons stands on unstable ground. The village is currently slipping down into the valley at a rate of roughly 1.5 m per year. The canton commis­sioned Stump-BTE to carry out core drilling in the village and directly in the mountain’s land­slide zone from 2018 to 2020. From March 2022, further drilling is slated to follow in an ex­plor­atory gallery.

The exploratory bore­holes between 2018 and 2020 were used to evaluate the conditions in the land­slide mass, which was up to 150 m thick. Since the fall of 2021, a follow-up measure was im­ple­mented in the form of an ex­ploratory gallery drilled into the aquiferous layer. The experts hope that they will be able to slow the land­slide by using this tunnel to drain the layer. During this process, the ex­pertise of Stump-BTE will once again be in demand, with the experts carry­ing out further ex­ploratory drilling in the gallery starting in March 2022.

The Drilling from 2018

The village is moving at break­neck speed. This is what made the geo­logists ask whether this process could be stopped. The basis for ad­ditional findings came from a drill core supplied by the specialists at Stump-BTE. For precisely this purpose, one of its drilling rigs in Brienz/Brinzauls south of Lenzerheide was already in operation from 2018. The team drilled under contract to the Department of Forest and Natural Hazards of the Canton of Grisons. The ob­jective was to learn more about the structure of the sub­surface all the way down to a depth of around 200 m. This was no mean feat.

Drilling operations were carried out using the wire line core drilling method. The team em­ployed a triplex tube for this. The outer tube bored into the sub­soil. The liner was located in the second tube, the inner tube. To recover the drill core, a winch was used to hoist the inner tube with the liner. The entire drill string re­mained in the bore­hole, which allowed the team to achieve the best core quality. This is essential be­cause geo­logists depend on the most exact bases possible. The main shifting zone at a depth of about 150 m was particularly interesting.

“We drill using the wire line core drilling method. After all, we cur­rently achieve the best possible core quality with this process.”
Martin Glück,

the stakeholders included

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