Well, uh...that's exactly what happened, especially in parts where the Atlantic Wall was thickest. Observe this beach in Pas-de-Calais, a similar stretch in Seine-Maritime, and other similar stretches of obstructions - mines and mine-tipped stakes in Pas-de-Calais, and angled mine-tipped stakes in Normandy - which is not yet looking into other possible types of beach obstacles, or the other components of the Atlantic Wall.

Could you clarify what you're actually trying to ask or what you're looking for here? As this is one of our more popular topics, I'd give it good chances I can dig up something that answers your question.