How did Hood's steel crushing tubes absorb blast energy?

How heavy were Hood's steel crushing tubes, and was the system practical as underwater protection?

The exact weight depended on tube thickness and packing density but ran to hundreds of tons, with the tubes absorbing explosive energy by deforming like a car's crumple zone.

No universal weight applies because the total depends on the thickness of the steel and how densely the tubes are packed. The complete installation nevertheless weighed hundreds of tons. The tubes were meant to crush under an underwater explosion and consume energy before the blast reached vital structure. Like a car's crumple zone, deformation was the mechanism rather than evidence that the component had failed to do its job. The system was practical in principle even though later water-filled arrangements could use the protective volume more efficiently.