How do engineers account for continental drift when building bridges and tunnels?


How do engineers account for continental drift when building bridges and tunnels?

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Not an engineer but… Land surveys would be the first step. Is the location fit for the bridge or tunnel? Tunnels would ideally not be built on a fault line or across a fault line if it is known to be active. As far as bridges- spacers get put in them to accommodate for expansion and shrinking due to temperature changes, that could accommodate some ground movement as well. And bridges generally have some amount of flexibility by design- in seismically active areas this would be an extra consideration.

They don’t. Bridges last 100 years and drift isn’t measurable over that short a time span. Also, most usually don’t cross tech tonic plate boundaries

They don’t build bridges or tunnels long enough that it would become an issue. They’re more concerned with local conditions like the bedrock being stable enough to take the weight of a large concrete structure and not chemically react to weaken it.

Continents don’t drift like stretching taffy. They creak and judder and largely stay rigid, shifting along lines known as fault lines. And they don’t move smoothly – they stay still for years and then there’s an earthquake and they move a lot (like, several inches) in a short time.

You typically don’t build a bridge straight across a fault line. If you do, it falls down in the next earthquake. You certainly don’t do something as dumb as tunnelling across a fault.

> The two towers were originally 1,990 m (6,530 ft) apart, but the Great Hanshin earthquake on January 17, 1995 (magnitude 7.3, with epicenter 20 km west of Kobe) moved the towers (the only structures that had been erected at the time) such that the central span had to be increased by 1 m (3.3 ft).

I’m not sure what would’ve happened if the bridge had already been completed when the earthquake occurred.