If I set a raised bed on a weed infested area. Say 2 foot dep. . Will the
weeds come through ,or will they die.

Hi there, this is my first post. It depends on the weeds. If they're things like dandilions they may do. I would glyphosphate them first and leave them for 24 hours then build the raised beds over them. This is what I've done on my current vedge patch that I've been preparing.

Glyphosphate breaks down very quickly in the soil so is safe. After you've killed the weeds it's probably worth diging the soil over before you build your beds, especially if your planting vedge.

I could be wrong about the above but it's my oppinion and that's what I would do. Hope that helps you out.

Dave