Cellular Geogrid as Basal Reinforcement to High Fills on Soft Clay / Clays with Low Shear Strength

[Mad Mike]

I have a major bulk earthworks project commencing in the next few months and value engineering is currently underway.

A costly aspect of the bulk earthworks is constructing high shale fill embankments over valley bottoms underlain by high plasticity transported clays. Rather than remove these clays (they are thick), I designed the new embankments to be constructed off a very high tensile strength (800kN/m) basal geogrid.

I've since been approached by an established engineering firm marketing cellular geogrids, comprising perforated geocells with very light uniaxial grids. The ultimate tensile strength on their uniaxial grids is just 50kN/m, however, I am being assured that by packing these cells (200mm depth) with a high quality crushed stone, the tensile performance will be every bit as great as the 800kN grids I had specified.

I'm having a very hard time believing this. My question is, have any of the geotech. guys used cellular geogrids as a single basal reinforcement layer to high fill embankments? I can picture it working in a number of applications, but a single layer at the base of a high fill embankment (40 - 60 feet) over a fat clay foundation is not one of them...

Thanks in advance,
Mike

 

[GeoEnvGuy]

I typically see geo cells used as surface erosion blankets in stormwater ponds. In terms of strength I connot say what would perform better in the short or long term.

 

[MTNClimber]

I haven’t heard of using geo cells in reinforcement applications. I would ask for the documentation providing the high strength value before considering it.

 

[Mad Mike]

I appreciate your responses- my feeling was exactly the same- I see it used in erosion and shallow soil reinforcement all the time, but I have a hard time believing it will work beneath a high fill embankment.

The documentation doesn't exist- there is a proven tensile strength on the geotextile (just 50kN/m), and then there is an "increased tensile strength", which is based on the performance on crushed stone packing in the geocells. The suppliers are unable to put a number to this increase, which is why I'm declining the project on this job.

All the best,
Mike

 

[GeoEnvGuy]

The research for geocells or geowebb can be found, such as the below study regarding bearing capacity and the minimal increase for gravels and moderate improvement for sand. However for someone suggesting the use of there product they should keep upto date with the research and be able to provide relevant studies.

https://www.semanticscholar.org/pap...-Han/30801a74aed163955e66085ad3fab6717a9715ff