Improving bearing capacity with geogrid

[samclane]

We are using geogrid layers in approx. 5' of gravel fill (remote site location)over soft silt with moisture content in 35-40% range. Looking for computational technique or software to help quantify bearing capacity increase. Does anyone have a recommendation? We estimate capacity of native material in the 200 psf range and would like to reach 1000 psf at bottom foundation.

 

[BigH]

One thing to keep in mind is that even if you have the "bearing capacity" aspects covered due to the geogrids, you will still have settlements due to your pad construction - on very soft clays, this might be relatively substantial. Have you checked out the literature of Tenex? I know it is for roads, but you might get a start there. There were/are a number of papers in the ASCE journals that I remember - but offhand, don't know the correct refs. Will think about this more.

 

[PEinc]

Contact your local Tensar Earth Technologies, Inc. representative. You can get their design program SpectraPave2.

http://www.tensarcorp.com

 

[VAD]

Why do you need geogrid when you are using 5 ft of gravel. What is the depth of influence of your footing.You need to look at this aspect before looking at geogrids.

 

[fndn]

You can take in-situ undisturbed samples of the silt just below the gravel and run direct shear or triaxial and use the c-phi to comput allowable bearing pressure. Then you can work backwards and assign a bearing pressure on top of the gravel, so you won't exceed the computed bearing of the silt. I suspect settlement will control, specially if the compressible silt thickness is more than the gravel cover.

A Member of

http://www.civilvillage.com

 

[sendy]

I agree with fndn, once the bearing capacity of silt is in hand, one can assign the required-thickness of gravel which is used for distributing the pressure to the silt. And I guess the bearing capacity won't be a problem (If it is a problem then one may think to use geogrid); The possible settlement is a matter that is needed to consider.

 

[eric1037]

Geogrid is good for limiting differential settlement if used properly. There will still be total settlement issues. Depending on how it is utilized (usually 3 to 5 layers) total settlement can be limited by up to 60%.

Tensar can provide engineering guidance.