Retaining wall leaning over?

Question

I have a retaining wall that I built two years ago. It is starting to lean in the middle. I used the connecting blocks that you buy at big box store. My plans is to tear down the section that is leaning dig out further and put new rock for backfill. The blocks are 6" x 12". I plan to put some weep holes in for drainage. The wall is about 6' high at the highest where it is leaning

My question is what can I do to prevent it from happening again.

What type of crushed rock do you use for back fill and drainage.

Also what about geogrid?

Thanks. I live in Minnesota. The size of the blocks I used were 6x12x6d. The wall is 5feet high. I used crushed rock and sand for base. It was mostly backfill with black dirt. I know I didn't use enough rock for drainage. It is between my garage and the wall is about 6' out from there. I don't have gutters yet so get a lot of runoff water so that could have caused some of the problem.

Answer 1

You might do best to contact a local stone yard. I just called my son in Phoenix for you. He's had lots of experience building retaining walls and is the manager of a stone yard there. He says that you didn't give enough info above to adequately answer your question. He'd need to know where you live (what kind of soil you have--whether it's clay or sand); the full dimensions of the blocks that you are using (L x W x H), etc. Also, the crushed rock has to be fairly big--no pea gravel, for sure. He mentioned using "slag" and compacting. You certainly don't want to make any mistakes the second time around. You need a really good foundation so don't use soil as the backfill, use slag sand. Slag by definition is the vitreous mass left as a residue by the smelting of metallic ore. We use slag here in the Detroit area because it is easier to work with and it is readily available in Southeastern Michigan due to the steel industry. Retaining walls require 4 to 6 inches escavation, depending on soil conditions. If your soil contains lots of clay, then excavate 6 inches. Your drainage problem needs to be addressed first.

Answer 2

Allow me to expand on the areas that Bonno touched on above.

Your ground behind the wall is expanding during the rain. this forces the wall outward. If the wall is top heavy toward the hill it retains, it will naturally settle back into its original place when the ground drys and shrinks. You can also turn an occasional block sideways so it will enter the soil and be locked in. Additional strength can be designed into your wall by creating an inside arc.

Can the water be diverted to the sides of the wall? if so, create a drainage ditch a few feet behind the wall and slope to the ends.

Answer 3

prevent - angle stack it back toward the dirt it is to retain

gravel - 5/8" to 3/4


geogrid allows water but reatains rocks so rocks & dirt dont mix, making the rocks useless!