As anyone who was at a typical archaeological dig knows, work safety is not always easy to achive. To be really safe, for example, it would be necessary to bank the sides of any trench after about 1.5 m of depth. Now this is unfortunately not possible if you want to document and analyse an archaeological profile... and there are many other conflicts between archaeology and perfect work safety like this.
Most archaeologists know about the risks. But since it's often a choice between take the risk or do not dig and document at all... the risks usually get taken, and most of the time luck is with them who wield the trowel and the showel. That said... situations like the one that you can see here (provided the link works - their server seems to be a little iffy) make me gulp.
So should you consider studying archaeology, or should you be one of the many folks who think they would love to be an archaeologist... it's not only hard and dirty work with not so much pay, standing in the exhaust fumes of big excavator machines sometimes, know that it often also means that you take quite a lot of risks - since you don't know what is behind a wall, or a trench wall, and you still go there and you still do the work.