Can't they like dig under the dome? Spoilers in case

[urrutiap]

It worked in The Simpsons movie

[M2H]

I am about halfway through the novel. I can't remember but someone in the novel "guessestimated" how far it went in the ground. At the same time, I don't know they couldn't dig but at the same time it's too "unhealthy" to physically get close to the dome. i.e. The Sheriff at the beginning