{"id":17581,"date":"2022-09-07T15:13:00","date_gmt":"2022-09-07T13:13:00","guid":{"rendered":"https:\/\/nyatunnelbanan.se\/?p=17581"},"modified":"2022-11-22T11:17:48","modified_gmt":"2022-11-22T10:17:48","slug":"tunnels-under-water-how-does-that-work","status":"publish","type":"post","link":"https:\/\/nyatunnelbanan.se\/en\/news\/tunnels-under-water-how-does-that-work\/","title":{"rendered":"Tunnels under water \u2013 how does that work?\u00a0 \u00a0"},"content":{"rendered":"\n

The longest underwater tunnel is the one from Kungstr\u00e4dg\u00e5rden to S\u00f6dermalm and Sofia station. At its deepest, it will be about 90 metres below the surface of the water. Naturally, working under a large body of water increases the risks during construction.<\/p>\n\n\n\n

\"Karta
Saltsj\u00f6n in cross-section. This is how the metro will run under Ladug\u00e5rdslandsviken, Saltsj\u00f6n and Hammarby Canal.<\/figcaption><\/figure>\n\n\n\n

Familiar with the geology<\/h2>\n\n\n\n

\u201cMuch of our work is about making sure we know the risks and how to manage them. When building under this much water, the risk of large amounts of water entering the tunnels increases simply because it\u2019s under such pressure. This is particularly true if the bedrock between the lake or sea bed and the tunnel is of poorer quality. This is why we have to be familiar with the geology, we need to know the structure and behaviour of the bedrock, how much water it lets through,\u201d says G\u00f6ran Leverud, project manager for the tunnel that will be built from Kungstr\u00e4dg\u00e5rden under Saltsj\u00f6n to Sofia station.<\/p>\n\n\n\n

\"G\u00f6ran
G\u00f6ran Leverud. Photo: Thomas Henrikson<\/figcaption><\/figure>\n\n\n\n

S\u00e5 unders\u00f6ks berget innan man b\u00f6rjar bygga<\/a><\/p>\n\n\n\n

The tunnels are constructed the same way as all other new metro tunnels in Stockholm \u2013 by drilling and blasting the tunnel out of the bedrock. In all tunnels, any cracks in the rockface are sealed with a cement mixture before blasting, which stabilises the bedrock and prevents water from leaking in.<\/p>\n\n\n\n

\"Stor
Drilling ready for injection. Photo: Region Stockholm<\/figcaption><\/figure>\n\n\n\n

Concrete tunnel under Saltsj\u00f6n<\/h2>\n\n\n\n

Three tunnels will be built under Saltsj\u00f6n \u2013 two for the tracks and one for service access. The service tunnel will be blasted first, and it will always be about 20 metres ahead of the other tunnels.<\/p>\n\n\n\n

\u201cThis allows us to check whether the properties of the bedrock are as we expected before we blast the metro tunnels,\u201d G\u00f6ran Leverud explains.<\/p>\n\n\n\n

In addition, under Saltsj\u00f6n, a concrete tunnel will also be built inside each rock tunnel, a so-called lining, to ensure a safe, stable and dry tunnel.<\/p>\n\n\n\n

Early in the planning process, studies were conducted to check whether it would be possible to instead build a so-called immersed tunnel, which is a tunnel built on top of the lake bed. However, this would have been considerably more expensive with greater impact on the environment.<\/p>\n\n\n\n

One advantage of building in the bedrock under the water is that the surroundings are not as affected.<\/p>\n\n\n\n

\u201cBecause we\u2019re far from the nearest building, as well as deep under the lake bed and deep inside the bedrock, we don\u2019t have to worry as much about the noise and vibrations caused by our work,\u201d says G\u00f6ran Leverud.<\/p>\n\n\n\n

Are fish affected by the blasting?<\/h2>\n\n\n\n

\u201cAnimal life in the water above the tunnel construction won\u2019t be noticeably affected. The pressure waves from the blasting won\u2019t propagate into the water above our tunnels. The sound waves, however, can propagate in the water and be perceived as unpleasant if you\u2019re in the water.\u201d, says G\u00f6ran Leverud.<\/p>\n\n\n\n

<\/p>\n\n\n\n

Where is the metro being built under water?<\/h2>\n\n\n\n
  • Ladug\u00e5rdslandsviken between Blasieholmen and Skeppsholmen<\/li>
  • Under Saltsj\u00f6n between Skeppsholmen and S\u00f6dermalm<\/li>
  • Two lines (tunnels) under Hammarby Canal<\/li>
  • Under Sickla Canal. <\/li><\/ul>\n","protected":false},"excerpt":{"rendered":"

    In several places, the new metro will run through the bedrock under water. Construction under water is conducted much the same way as anywhere else, although it does requires good familiarity with the geology.<\/p>\n","protected":false},"author":4,"featured_media":17344,"comment_status":"closed","ping_status":"open","sticky":false,"template":"templates\/template-press-news.php","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[87],"tags":[],"class_list":["post-17581","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/posts\/17581","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/comments?post=17581"}],"version-history":[{"count":8,"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/posts\/17581\/revisions"}],"predecessor-version":[{"id":18397,"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/posts\/17581\/revisions\/18397"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/media\/17344"}],"wp:attachment":[{"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/media?parent=17581"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/categories?post=17581"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nyatunnelbanan.se\/en\/wp-json\/wp\/v2\/tags?post=17581"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}