Slope requirements?

[thebig450es]

One of my friends asked me to come take a look at his house where the hill behide it slid back in the summer. What is the rule of thumb when grading the slope is it 34*, 45*, or can i go up to a 53 deg. slope. The soil is western PA clay.

 

[rino1494]

If the slope slid before, why would you want to go that steep. I wouldn't go more than a 2/1.

 

[thebig450es]

Well, its about 2 feet up the house on the one conor and is close to a 45 for about 10 feet and then 25 for about 200 feet

 

[thebig450es]

he wants me to make a 3 foot path behind his house, so the hill isn't as close to it. I told him to find a professional to do itbut he said he didnt have the money

 

[stock]

he wants me to make a 3 foot path behind his house, so the hill isn't as close to it. I told him to find a professional to do itbut he said he didnt have the money

????? your not professional?? any chance of a 1000 words or a picture maybe two.I would recommend a retaining wall where it is steepest; but as I live on the other side of the pond and not familiar with your local codes or type of ground conditions i will leave it at that.

 

[thebig450es]

well i dont specialize in the area of land slide rentention lol , im more into the septic systems. I'll get some pics asap.

 

[CM1995]

One of my friends asked me to come take a look at his house where the hill behide it slid back in the summer. What is the rule of thumb when grading the slope is it 34*, 45*, or can i go up to a 53 deg. slope. The soil is western PA clay.

Is this a cut slope? The angle in which a slope can be cut depends on the virgin material. Different soils have different angles in which they will remain stable. Other factors include rock, ground water, different soil types located in the cut slope, etc.

The whole slope may need to be re-graded and/or a retaining wall built. I would suggest your friend contact a geotechnical engineer to perform a proctor and a shear test to determine the angle the material in the slope will safely stay put. This info would also help in design of any retaining walls if needed. Of course if your friend doesn't have enough money to hire a "professional" then he may not want to go that route.

Either your friends backyard slope was cut at too steep of angle for the material or it was over-excavated and then re-filled, thus causing the slide. If I were you I wouldn't mess with this unless you want to lose a friend.

 

[td25c]

Ground water /wet springs

Pictures of the site would help.We have some slides in my area and its all due to ground water.Might try a surface diversion well above the slide to take care of rainfall,then a sub-suface perimeter drain just below the surface drain.dig it in & install drain tile ,backfill with #2 stone to catch the ground water. If you can dry up the hill,it wont slide anymore.

 

[thebig450es]

Here is a pic. The house has been there around 50 years and the reason the hill slid was because of a rain we had ( 6 inches in an hour). I told him, we can try to come up with something but i can't be held liable for anything that may happen, and he understands that.

 

[td25c]

Dang thebig450es! That looks like South Indiana hillside.Common problem here.I'd get up about 100 feet above the home and do a surface diversion drain now to keep the water away from the home.Then when your buddy has the money,put up a retaining wall behined the home.Gotta love them hills as they give us dirt diggers & concrete slingers somthing to do.

 

[cat 385]

it looks like there is plenty of moisture still judging from the cracks right where he wants it away from the house,if you start digging at the bottom it will probably keep coming,i don't know how dense the clay is but it could be holding back a lot of water,i would want to get rid of those trees close to the house but i think the are holding the hillside some.this is just my speculation from what i can see from the picture.i would say a retaining wall is cheaper than a new house.good luck.

 

[thebig450es]

I think we all agree a retaining wall and drainage is what is needed. I saw it right after it happened and it hasn't changed much if any in the past 6 months. removing the trees are almost a double egde sword, I'll need to remove a few of them atleast.

 

[thebig450es]

Im thinking of placing drainage alittle above the red line and then grade down to the green line.

 

[cat 385]

ya, if you start away from the house say like to the left on your picture you could get an idea of what it is going to do,what are you going to use for drainage?

 

[heavylift]

i would be worried about moving what ever is holding the mountain... you may move the wrong rock then down the hill it all goes...

the trees could be the entire problem. their roots may have gone down just a few feet then spread out. Like carving a slice of turkey. You may just have a thin slice of earth ready to slide down the mountain...I'm guessing

THink of it as a slice of bread with that turkey and stuffing on top.... but all that rain (mayo) is on the bottom of the turkey... Now turn the bread at a 45 degree angle ... that dang Mayo let the turkey slip all the way to the bottom (floor)...

still I think he needs an engineered guessimate... You know how insurance companies are...

 

[td25c]

Thats what I would do the big450es for now.Put in a surface type drain then later as money allows build a concrete wall behined the home.Good luck with it.

 

[supt]

Thats what I would do the big450es for now.Put in a surface type drain then later as money allows build a concrete wall behined the home.Good luck with it.

I agree. The right way in my opinion would be to put a retaining wall in with drain tile above like you mentioned. In addition, I would backfill the retaining wall with clear stone and install drain tile directly behind the wall at the top of the footing. The wall should be high enough however, so that you don't have to change the grade down to it by very much. I would suggest the wall to be at least a 10" wall, 4000 psi, with piers, on a 10" deep x 30" wide footing, and follow the footing around the piers, with plenty of re-bar both vertically and horizontally in the wall.

 

[td25c]

Welcome to the forum supt.Your plan sounds good.I forgot to mention to thebig450es about installing gabion wire baskets as a retaining wall.We use them in waterways & ditchbanks.They seem to work pretty good.They dont need any drainage behind them as they are filled with "rip-rap",ground water just flows through them.They hold back the ground good.

 

[thebig450es]

I like the idea of using the baskets, where is a good place to get them and what type of fill do you reccommend.

 

[heavylift]

www.gabionbaskets.net
that just a site I googled...
I've worked around them .... They had a machine with hog rings that put them together... then laborers stacking them .... and more hog rigs...
We used 5 x 9 rock... at least I think that's the size.... they would set a basket then fill it with a hopper then hand place a few rocks. then staple the top

they use them a lot . but they usually end up just being weed planters
and appear to hold up well