Many replies mention expansion joints. There are also other techniques that can be used: for example pre-stressing as is done with continuous weld rails: https

Many replies mention expansion joints. There are also other techniques that can be used: for example pre-stressing as is done with continuous weld rails: https://en.wikipedia.org/wiki/Rail_stressing https://en.wikipedia.org/wiki/Rail_stressing Overall, it is not a particularly difficult engineering problem.