Hallandsås Tunnel

Construction began in 1992, and the traffic opening was originally planned for 1995. However, construction was plagued by major difficulties concerning large amounts of water seeping in from surrounding rock, only a small fraction of which had been foreseen. Additionally, the original drill, which was said to drill 100 meters per week, broke down after drilling only 18 m (59 ft). The rock was too soft, so the machine could not use it to pull itself forward. The contractor tried to drill traditionally, but had to spend a lot of effort on sealing the water leaks. The contractor went bankrupt and a new contractor, Skanska, was contracted. The new contractor had similar trouble but a better contract that gave compensation for troublesome rock conditions.

A scandal broke out when it was learned that a poisonous sealing compound Rhoca-Gil was used during construction. This substance was linked to the death of nearby livestock. Rhoca-Gil contains acrylamide, a toxic chemical that is mutagenic and possibly carcinogenic. The main contractor, Skanska, took no special precautions for the sealant, nor did it tell its own workers or the local population of the risks. By October 1997, local cattle and fish started dying and workers were becoming ill. The local press started an investigation. After tests were done showing high levels of acrylamide contamination, the site was declared a high risk zone and the sale of agricultural products from the region was banned. Skanska, along with Rhone-Poulenc and Swedish Railways all had criminal charges brought against them; some senior executives resigned as a result.

Construction was halted in late 1997. By this time, nearly 3 km (1.9 mi) had been bored in each tunnel: 1,200 m (3,937 ft) at the north end, 1,700 m (5,577 ft) at the south end, and 40 m (131 ft) at the central adit).[1]

In 2005 construction resumed after a positive decision by the Riksdag and the Swedish government, hydrological and environmental remediation by Banverket and Skanska, and selection of contracting consortium Skanska-Vinci for the project. A new completion date of 2012 was initially estimated, later being revised to 2015.

As the consortium decided to drill only one tunnel at a time, only one tunnel boring machine (TBM) was used for the revived project. Nicknamed "Åsa", the TBM was in reality a comprehensive tunnelling machine; as it drilled through the strata, it simultaneously installed precast concrete tunnel lining segments behind it, and then injected a mortar-and-gravel slurry into the voids between the strata and the lining. The problem of drilling through saturated rock and soil was tackled by drilling a pilot tunnel ahead of the TBM, then freezing the surrounding rock to a temperature of −40 °C (−40 °F), thereby guaranteeing solid strata for the TBM's progress.[2]

On 25 August 2010, around 13:10 CET, breakthrough was achieved in the eastern tunnel. Drilling then switched to the western tunnel, which started in March 2011 from the workface at the south end and proceeded north. On 3 April 2012, this drive reached the central adit, whereupon 2,517 m (8,258 ft), or 46 percent, of the western tunnel had been bored.[3][4] The remaining 1,144 m (3,753 ft) to be drilled, which totaled 15 percent of the entire drilling project, was expected to be particularly challenging, as it contains a section of poor quality bedrock and significant amounts of water and water pressure.[3] An extra freezing stage, plus extra time (4 to 6 months) allotted for freezing, and thicker concrete lining segments, was utilized in this 300 m (984 ft) problem area, which is longer than the adjacent area encountered in the eastern bore.[5] On 4 September 2013, the second tunnel broke through.[6][7]

There are 19 emergency cross-passages (including the central adit) between the two tunnels every 500 m (1,640 ft). These were bored and lined separately, a process completed in February 2014.[8][9]

The opening ceremony was held on 8 December 2015, and the tunnel opened for traffic on 13 December.[10]