I'm curious as to the maximum heights and other limiting factors for the sytem you describe because it does not have the porosity to allow water to seep back into the sea after washing over it. This factor what eventually causes all the sea walls around here to fail sooner or later.
The beauty of the geo-tube is that it's just sand in a very strong porous bag. The water seeps through it - sand is left behind, but the water goes back to the sea. The stones under the piers have a similar property although they are not as stable because a big storm can move them around if they are not contained.

Anyway - sounds like my groyne story and your cement bag story are about two different systems - each having an application in various settings. All valuable info and yes I'd be very interested in seeing the info you have. I'll PM you with an address to send.

As Bucky Fuller said ...... "You can only learn more - it is impossible to learn less!".