Earth Drain side slope

[Da CnS Engr]

Hi all,

I have an earth drain constrained to a size of 2.5m top width, 2m bottom width, 1.9m height, which would give the side slope 1:0.13 (H:V), can I reinforce the side slopes with gabion mattress? Or any other types of lateral reinforcements?

If not, what is the limit of the side slope that I can use? 1:0.5?(H:V).

Thanks.

 

[1503-44]

Your diagram shows a slope of 800%, a rise of 1 over a run of 0.13
That's essentially vertical.
It's possible to use a gabion, or a reinforced concrete wall.
Natural unprotected slopes are typically limited to a rise of 1 over a run of 2. You're nowhere close to that.

 

[Da CnS Engr]

Yes I'm aware of that.. but I'm pretty limited on the width thats why..

How about a 1:1.5 slope? Can the gabion hold it?

 

[TigerGuy]

Do you have room to install some tiebacks?

 

[1503-44]

Gabions can be made vertical, if enough width is available. After all it is a gravity design.

 

[Da CnS Engr]

@TigerGuy, yes I do have enough room for tiebacks but dont think its feasible in terms of cost, the earth drain/swale is approx. 1000 metres long.

@1503-44, do you know how to check the capacity?

 

[Da CnS Engr]

Attached is the typical detail drawing

 

[1503-44]

You can't use mattresses in the vertical. They're for horizontal lay.

You need gabion blocks, more like this, each block about 1m3, set back each block course an additional 0.25m into the sideslope as you lay each course.

A mattress might work to cover the bottom between the two walls on each side.

Capacity

Design as a gravity retaining wall. The 1.5 times the retained earth thrust outward must be counteracted by the weight of the blocks x distance of CG to toe.