400 meter long Hellerud tunnel on the Østensjøbanen in Oslo has been excavated. But it comes with the warning from the project management that the project will be more expensive than expected.

Report from Byggeindustrien (Construction Industry):

https://www.bygg.no/gjennomslag-i-ny-t-banetunnel-men-oslo-prosjektet-blir-dyrere-enn-antatt/1503909!/

VårtOslo: 60,000 passengers can have shorter journey times on the subway's lines 2 and 3 when the new tunnel is put into use next autumn.

https://vartoslo.no/bydel-ostensjo-per-magne-mathisen-sirin-hellvin-stav/det-ble-lys-i-enden-av-den-nye-t-banetunnelen-en-gledens-dag-for-ostensjobanen/394300

Project owner is infrastructure and projects dept of Sporveien. Excavation had started on April 4 this year.

The tunnel has been excavated with traditional tunneling, by first drilling and then blasting into the rock. Extra Avisen has a lot of details, if anyone interested in reading Norwegian:

https://www.extraavisen.no/gjennomslag-i-den-nye-t-banetunnelen/