embankment fill on slope

[longisland]

hi all,
Can someone shed some light on embankment filling on sloped ground?
What's the steepest allowable natural slope a 2:1(h:v) embankment can be constructed on top assuming no slope stability & bearing problem to the natural slope. In another words, the gradient which machinery can perform compaction to requirement on site. I mean heavy machinery such as roller compacter or sheep foot

thanx

 

[Krautso]

If this natural slope cuts across your cross-section, can you bench out the existing hill prior to building your embankment? Benching will help any possible slope stablility problem and allow the contractor to build a level surface for constructing the embankment. This also makes it easier to build in lifts and of course would remove the risk of having a packer roll over during compaction. This works better when the native soil is suitable for incorporation into the subgrade.

 

[glennd]

I agree with Krautso. if you are working along the contour (or close to the contour) you can construct the emabnkment in lifts allowing for a flat working surface to comapct as you go along. trying to compact on a slope is difficult and vehicles such as scapers and sheeps foot rollers have difficulty in working on anything steeper than about 1 in 3.

this technique is often used when rehabilitating earth dam embankments or levee banks.

 

[n3rei]

Oh! and let us not forget OSHA for maintaining the slope.

 

[Makis]

I agree with the above methods, a couple of other comments to consider would be to make sure that any roots, stumps or topsoil material is removed first. Another option is too build a level lift as suggested above, but key each lift into the existing slope by approximately 1 meter. This I believe would be the ideal situation, but you should discuss this with the Contractor first, as They may request an extra on this work.

 

[Jim6758]

Advice above is very good. 2:1 is pretty steep and cannot be safely mowed. You might consider modular block walls stepped back at reasonable intervals. There are some geogrids put out by Contec and Mirafi that can be used to stabilize a steep slope. You can then plant low growing plants such as Ivy which doesn't have to be mowed.

 

[dicksewerrat]

With 2:1 slope look for 'native' plants and turn the slope into a small' back to nature' site. It usually requires no maintenance. and you can probably get free help in the planning from a University. In Minn. we call them 'natural prairies'.

 

[Grader]

Depending on soil conditions, purpose of fill, structural integrity, etc., the most common maximum fill slope is built at 2:1. Steeper slopes can be engineered with the help of your soils engineer, if required. Many times a combination of geo-grids, retaining walls and earthen fills will be your best solution in hillside areas. Depending on the size of your project, normal grading equipment can build on extreemly steep slopes with the propper room to work. There are many issues to consider, I wish I had more information to go by.

 

[wolfhnd]

Something else to think about is drainage. If your working on the side of a hill you will block a spring or two and that can easily damage your fill.

 

[alwyn511]

what about a complete analysis to predict the performance or stability of your embankment during and after construction? An undrained case, i.e. a total stress analysis, will have to be considered. the slope of the emabankemnt must be related to the strength parameters of the borrow (fill) to ensure stability of the slopes. a non rigorous approach may be taken for designing your embankment. mention was made of drainage? What about seepage? that too must be considered as the embankment may failed because of piping, which is initiated by seepage forces.

 

[nawzadbilal]

Hi,
Ifully agree with (alwyn511) and there are different softwares for checking slope stability but first you should have the cohesion and internal angle (theta) so a lab. test for the borrowed soil is necessary, also mannual simplified Bishop method will be good for this case if it was not a huge one.
Nawzad

 

[KRSServices]

In additiona to the comments already provided, you should carefully evaluate the construction procedure to be used. Last year I had the dubious task of repairing an embankment fill on a highway, originally installed 10 years ago, that sheared due to a slip plane 3.5 m below the constructed fill. The cost, $1.2 million, need not have been spent if a detailed evaluation was carried out first. Albeit, this is a worse case scenario, but the probability of other geological factors affecting your design should be ruled out. KRS Services

http://www.krs-services.com