Qing-Huang vs Eiksund: length, opening date and class compared

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Side by side

Qing-Huang is recorded on data/subsea.html and Eiksund on data/subsea.html, compiled to the same convention, which is what makes the two figures comparable at all.

How this archive measures: lengths, bores, dates and ordering

How this table is compiled

Qing-Huang and Eiksund are compared here on the figures this archive records for each, taken from the same sources and the same measurement convention. Qing-Huang belongs to the 2010s and Eiksund to the 2000s, two decades in which what a tunnel had to provide by way of escape and ventilation was not the same thing.

That gap is about 0 per cent of the longer bore, which is the figure worth holding on to rather than the raw metres. Driven end to end the two would run 15.6 km, which is the figure to hold against the 10.8 km of the longest single subaqueous tunnel in the record.

Both rows are reachable from the subaqueous tunnel table they were taken from, where the note column carries the tube count, the gradient and any reconstruction Qing-Huang or Eiksund has had. Across every class this archive records, Qing-Huang stands 165th by length and Eiksund 166th, so the pair sits inside the top 166 of 244 structures.

58 other structures in this record opened within two years of Qing-Huang, which is the cohort it was designed alongside and the fairer comparison for how it was built. The 2000s account for 53 entries in this archive, and Eiksund is one of them, which is the context a single opening date does not carry on its own.

Neither holds the record: Sandoy at 10.8 km is the longest subaqueous tunnel recorded here, 3 km ahead of Qing-Huang. A disused rail bore is the commonest cycleway in some countries, which is a second life a length ranking cannot show. Smoke moves uphill, so the two portals of a burning tunnel are not equally dangerous.

Reading the figures

Both are recorded in this archive as subaqueous tunnels, so the measurement convention is identical and the comparison is direct. 164 recorded structures are longer than Qing-Huang, the nearest of them Bømlafjord at 7.93 km. The interesting figure on most crossings is the gradient or the cover, and neither appears in a ranking by length.

Adding a metre to the longest tunnel in the world costs what adding a kilometre to an ordinary one does. Nothing in either row is estimated: a value that could not be corroborated is left blank rather than filled in. A short bore beneath a city can cost more than a long one through a mountain.

Qing-Huang was designed under the modern regime, with cross-passage spacing and emergency ventilation specified from the outset. Among the subaqueous tunnels this archive records, Qing-Huang stands 5th by length and Eiksund 6th, adjacent in the ranking. Fixed links change settlement patterns, so the traffic a crossing carries later is not the traffic that justified it.

Environmental consent now outlasts construction on many schemes, and the dates in a record rarely show it. Wartime damage closed several crossings for years and a few were never reopened to their original use. Comparing two national records says as much about how each country documents its infrastructure as about the infrastructure.

Depth below sea level is recorded where published. Length is measured portal to portal. Nothing on this page requires scripting to read. Sources are named on each structure's own table. A pilot bore driven ahead of the main tunnel is usually kept afterwards as the escape route. The longer bore is not the harder job.