Spiny Norman said:

What Went Wrong? Australia’s $15 Billion Pacific Highway Mega Build.

Discover the extreme construction of Australia’s massive 15 billion dollar Pacific Highway Upgrade. Stretching across 155 kilometres, this megabuild forced teams to tackle bottomless coastal swamps that behaved like liquid mud.

Learn how they prevented a massive highway collapse using millions of metres of vertical wick drains, concrete injected columns, and high-strength geotextiles.

From deep-water bridge foundation crises to explosive hard-rock tunnelling through tough basalt, we look at the high-pressure reality and extreme physics that saved countless lives on Australia’s deadliest road corridor.

https://www.youtube.com/watch?v=5AHKl-EIpig

More interesting and far more difficult than I thought it would have been.

I suspect there is a little bit of hype in all that, but should be QI anyway :)

Will have a look later.