[j_ten_man]

The wall is 4 years old at this point. These are two rocks at the bottom of a nearly 10 foot wall. I don't care about the look, but am wondering if this is a serious issue I need to address, or it should be fine?

 

[stadry]

think your rocks are crumbling due to 'point loading',,, looks like a dry laid wall,,, mortar serves 2 purposes: 1, makes chipmunk tunneling more difficult; & 2, spreads the static load to those supporting stones
or so it seems to me - then again, you just couldda got stuck w/couple bad stones

 

[j_ten_man]

If you look at the other rocks around the main rock, you'll see that the big ones aren't the only ones that are crumbling like that. There are several that are. I would say probably 1/3 of the rocks have started to crumble and break like this, so definitely not just a couple of bad rocks.

 

[Bondo]

Ayuh,...... Yer rock wall, will be a crushed stone slope in 'bout 40 years,......

 

[j_ten_man]

I'm fine if it's 40 years. I'm just worried about the next 2-5 years.

 

[SPS-1]

I am certainly no rock expert, but you can see the internal and external layers on those stones, which means its a sedimentary rock.

Sedimentary rock can be quite soft apparently.
Its just sediment that was fused together by years of pressure.
Link

So could be that after a while you will have a bunch of smaller rocks. No way for me to predict how quickly the rocks will deteriorate or how much strength is required by the geometry of your wall. A geotechnical engineer could give an opinion if this is in a critical application. But myself, I would not worry about it until if and when I saw the wall moving.

 

[j_ten_man]

I am certainly no rock expert, but you can see the internal and external layers on those stones, which means its a sedimentary rock.

Sedimentary rock can be quite soft apparently.
Its just sediment that was fused together by years of pressure.
Link

So could be that after a while you will have a bunch of smaller rocks. No way for me to predict how quickly the rocks will deteriorate or how much strength is required by the geometry of your wall. A geotechnical engineer could give an opinion if this is in a critical application. But myself, I would not worry about it until if and when I saw the wall moving.

Thanks. I may want to call an engineer then - this is in the front of my house and holds my driveway up. If it went, I'd lose a driveway.

 

[joed]

No rock expert here but it looks to me like the wrong type of rock was used. An engineer is good idea.

 

[HotRodx10]

That's definitely what we'd call "heavily weathered" rock. It has significantly less strength than intact rock, but its strength may still be sufficient; a geotechnical engineer, or an engineer with a geotech background should be able to give you an estimate of how long before it becomes unstable. It will probably be a broad estimate, so you will likely have to weigh the consequences of failure. I can't tell for sure, but it looks more like a steep slope than a wall, in which case 'failure' would consist of it mostly sloughing. If there isn't a risk to life or limb, and it's a 'fix it now or fix it when it fails' kind of choice, you don't have alot to lose by waiting. However, if it could cause damage or injury if it fails, that changes things. The geotech should be able to tell you the likely failure mode, as well.