Pressures on the back of retaining walls due to ballast in close proximity

[MattMontgomery]

Hello,

Quick question, I was having a bit of a discussion with my director, whether or not you get full pressure on a retaining wall if you do not have continuous conditions.

The problem is, we have 2 retaining walls of approximately 800mm high, at 400mm from eachother, with ballast (40mm granular fill, ungraded) filling up the void between. I was arguing that ballast does not work like water, and we do not take the full height of ballast as the effective "head" because the pressures are distributed differently and there is rigidity that comes into play, as it is not a liquid. Surely if the wall pressures actually begin to move the wall, there is much less ballast within the wedge to push the wall outwards?

Please could someone confirm to me the system in which this works? Should it be full height of ballast pressures, or does it reach an equilibrium?

 

[GeoPaveTraffic]

Are you saying that the two walls run parallel to each other and are 400mm apart? If so, then the pressure could be reduced. Look up equations on silos.

Mike Lambert

 

[bimr]

You are correct in that it does not like water. Here is a pdh that explains it.

http://www.pdhonline.org/courses/c155/c155content.pdf

 

[Panars]

There have been other good discussions in other threads going back a few years.

thread486-185817: Retaining Wall 2 ft from Rock
thread274-166357: vertical and lateral earth pressure - length req'd
thread507-193368: Parallel Retaining Walls

 

[MattMontgomery]

sorry for the slow reply back,

yes I was indeed, the 2 are in very close proximity and thus it is more like a massive filled trough.

Thank you for the pdf, I'll make sure to look at it when discussing this in future.