With a 16 year delay the second tunnel through Hallandsåsen is finished.

Hallandsås Tunnel - Wikipedia, the free encyclopedia

By the end of August 2013, a total of 5,379 m (17,648 ft) or 99.1 percent of the western bore had been drilled, and on 4 September 2013, the second tunnel broke through.^[6][7]

This will enhance train communications between Malmö and Gothenburg, as the existing single track winding around is a bottleneck. However it is also a cautionary tale against trying to tunneling through a porous ridge on the cheap. The first attempt in the 90'ies ended quite badly.

Hallandsås Tunnel - Wikipedia, the free encyclopedia

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 broke down after drilling only 18 m (59 ft). A scandal also broke out when it was learned that a poisonous sealing compound called "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]

The new attempt (from 2005 and onwards) instead used a slower, more expensive but in the end mre effective technique.

Hallandsås Tunnel - Wikipedia, the free encyclopedia

. The TBM, nicknamed "Åsa", is a comprehensive tunnelling machine; as the TBM drills through the strata, it simultaneously installs the precast concrete tunnel lining segments, then injecting a mortar-and-gravel slurry into the resulting voids between the strata and the lining. The problem of drilling through saturated rock and soil is being tackled by drilling a pilot tunnel ahead of the TBM, and then freezing the surrounding rock to a temperature of −40°C (−40°F), thereby guaranteeing solid strata for the TBM's progress.^[2]