sandstone wall

[IngNicola]

I'm modelling a problematic stone wall. This wall is a retaining wall and i have measured that the wall rotate and move (respect the foundation). Probably the cause is water or some yielding. The wall starts with 0.8 meter of height and arrive at 3.3 m. Thickness is 0.45 m e the lenght of front is around 25 m.
How can I modell this wall? Where can I take the exact property of the sandstone? of course it's a material that resists only a compression and not a traction.

Thank you

 

[oldrunner]

Why are you modeling this wall? This appears to be a fairly simple gravity retaining wall that can be easily and quickly done by hands calcs.

Do you have a soil report which tells you the allowable bearing pressure and friction factors? Do you have the active pressures and surcharges?

Is there drainage behind the wall?

 

[IngNicola]

> This appears to be a fairly simple gravity retaining wall that can be easily and quickly done by hands calcs.

Of course it's a simple wall (if I have to make new, but it's already existing). I have to modell because I want to see when this wall'll collapse and studying a good solution (for instance some piles which should be in contrast of the movement of the retaining wall and so studying concentration of tensions)

>Is there drainage behind the wall?

No

> Do you have a soil report which tells you the allowable bearing pressure and friction factors?

pressure = 0.8 kg/cm2
friction factors = 22°

In general how can you modell a sandstone wall?Have you some practice tips?

thank you

 

[oldrunner]

Basically I only will model a retaining wall if is has an odd geometry. You didn't say what the active pressure is on the wall or if there is any kind of surcharge.

To me, the easiest way to find out the weakness's of the wall is to set up a simple spread sheet and then increase the loads until I get either tension in the sandstone or if the bearing pressure on the toe is higher than the allowable. If the wall is already rotating, I would hazard a guess that the there may be a soil failure occuring.

Are there piles under the footing of this wall? (You did mention them). In this case if there are front piles in compression they could possible be not adequate. If there are piles at the rear of the wall, they would have to work in tension and they may be failing and the wall rotating about the front row of piles.

In this case, your geotech should be providing you with some design friction or point bearing factors of the compression piles and then a different friction factor for pull-out.

 

[IngNicola]

> Are there piles under the footing of this wall? (You did mention them).

This is one of the solution for stopping the movement of the wall. But I need to know how can i model (if possibile) a plate (o something else) where every elements are disconnected each other (no tensile material). I think this is a general problem about modelling masonry wall with FEM program, isn't' it?