Aerial photo of a barrage, location and date unknown. As this photo shows, a barrage "covered" an area, but that really did not mean that nothing in that area could live. Most defenders in the shell-swept area would probably have their heads down, which was the goal, but they might well survive. This also shows that the shells did not all fall on a single line, even when they were supposed to.
Source: IWM photo Q27221.