Wierd Stone Special Cannonball Resistance.

[Inhapi 0]

I admit, this has little or nothing to do with AFV armour, yet i think it might be interesiting for those into fortifications:

 

How the fort at St. Augustine was able to resist cannonball impacts due to the special nature of the stone used in its construction:

 

https://www.atlasobscura.com/articles/coquina-fort-in-florida?utm_medium=atlas-page&utm_source=facebook.com&fbclid=IwAR38zhas0B2x4pwJaxVPh0qv8jp9qOJt0rHmHo6e4qOkI5AVbqTiG4FE_O8

[KV7 0]

Good find. I always wondered why they didn't just earth ramparts ahead of thinner stone on standard forts.

Edited January 3 by KV7

[RETAC21 0]

I can answer this: It’s not clear whether the Spanish had known about coquina’s properties when they first built the walls,

 

The answer is yes, most of Cadiz is built with the similar piedra ostionera

[Inhapi 0]

Good find. I always wondered why they didn't just earth ramparts ahead of thinner stone on standard forts.

 

 

Well there were different schools of tought about that.

 

You could go for almost entierly earth ramparts (indeed whole forts), but then you run into the risk of the fort being easier to storm by surpirse or an overwhelming force due to the slopes in earth being relatively flat.

This was the method chosen by Benno van Coehoorn, but he could in a sense get away with it because in the low countries he could provide his forts with wet ditches, thus make them essentially storm-proof;

 

Vauban otoh mostly had to build forts with dry ditches (there are exeptions in north west France). hence he felt the need for stone ramparts to get a fortress that was proof from being swamped by massive infantry or by surprise by a smaller force. now you have to take into account that Vauban did realise the vulnerability of masonry work to artillery. he tried always to cover the masonry walls behind detached earth works backed by masonry support (i.e. sand in front of the masonry). it is this refined interplay of stone crutain walls covered from direct fire by earthen works that form the core of the "Vauban system" , if we can call it that. The general bastioned fort principle was developed way befor Vauban, but he made them much more resistant to artilery.

 

In the 19th century, before the advent of concrete, we see that e.g. Brialmont elvolved his designs quickly to being stone cored structures with heavy earth cover in front (and on top of them). This general principle was later followed by Séré de Rivières in France.

 

there is much more to it, but i guess this gives an outline....

Edited February 3 by Inhapi

[DougRichards 0]

Another aspect is that soil ramparts needed quite a bit of maintenance, as water tended to erode them.

[Inhapi 0]

Another aspect is that soil ramparts needed quite a bit of maintenance, as water tended to erode them.

 

Indeed; and the growth on them has to be removed constantly (and this conflics ofc with anti erosion measures). You often read about earth fortresses being covered in high grasses, shrubs and even trees that had to be removed to bring them to a defensible status.