Rock retaining walls pit friction against gravity
You may have learned why the stacked brick works in your high school physics class. (It’s possible you’ve been sick this week, so I’m going to loosen you up a bit.) There are several different formulas that could hurt your head, but it’s all about bulk and friction.
The floor behind the wall reacts to gravity. It wants to be drawn closer to the center of the earth. Any retaining wall that works is designed to provide a force greater than gravity, thus holding back the slope for a while, no matter how big it is.
Think how easy it is to push a baseball-sized stone across the floor. It doesn’t take much effort. Try pushing a square boulder the size of a dishwasher and you will have to enlist the help of a few friends.
Here are some tips to help you succeed in building a retaining wall out of stacked bricks. The first step is to dig into the ground and remove the topsoil from which the base of the wall will be anchored. You want the wall to be at least six inches in the ground, although 12 would be better.
If you want the wall to be taller than three feet, you should tilt the face of the wall so it leans back into the slope. The forces pressing against the wall increase exponentially as the wall gets higher. If you double the height of a typical wall, the compressive force to tip over can be three or four times greater.
A stacked stone wall relies on its own weight and the friction between the stones to hold the ground back. Larger stones work best, but make sure the size of the rock matches the overall look you want to achieve.
I have a collection of retaining wall columns on my askthebuilder.com website, including excellent photos and diagrams in case you want to dive deep into the subject.
Tim Carter can call you for free to solve your problem. Go to his website and fill out the form on this page: www.askthebuilder.com/ask-tim/.