Reinforcing foamed glass gravel with geosynthetics

logo_smallWe are used to build on stable terrain and disregard the possibilities of less stable ones. But sometimes, we have not the choice (we don´t make a curve with a railway due to terrain conditions) or we can buy such a land at a very good price. In these cases, we can use geosynthetics to stabilize the terrrain.

GLAPOR PERMAFROSTWith GLAPOR cellular glass gravel, it is advised to use a geotextile to separate the gravel from the soil. Without using this textile, intermixing between gravel and soil will induce a cold bridge into the gravel. In the picture on the right, this textile is called geogrid. In reality, a geotextile is used with the following specifications.

A gravel bed is only loaded in compression or shear and can be described as a cellular structure based on cellular glass. This gravel bed does certainly not behave as a beam, it has no bending strength at all. As a consequence, all the bending strength of the system has to come from a (concrete) plate on top of the gravel.

CellularConfinementSystem-HexBut today, we have also cellular confinement systems, also known as geocell. The brand name Geocell Schaumglas is also used for foamed glass gravel, but this is clearly not what we mean, when we speak about geocell. The picture on the left shows an old application in Alaska.

footsettlementThis geocell  structure, filled with clay, induces an important extra bearing capacity compared to unreinforced clay like shown in a paper paper. Like can be observed in the graph, the effect is dramatic if geocell and geogrid are used. For a settlement of 20%, we have an increase in bearing pressure of at least a factor 3. This is defined as the load bearing improvement factor.

PRS roadThe (beam) effect is also demonstrated in a paper paper about improved road constructions with geocell reinforcement. Indeed, the geocell helps to distribute the load of a tire over a much larger surface, increasing the life time of the road. In this case, the experiments were done with PRS Neoweb, a geocell based on Neoloy. This polymer is an improvement, compared to HDPE, which is usual used for geocell.

At this moment, we can ask ourselves what we can do with a geocell, filled with GLAPOR cellular glass gravel? At least, the application in the previous post will be improved. Indeed, roads on foamed glass gravel will have a much larger life time. But in a lot of cases, we can construct a lighter structure than with ordinary gravel, thanks to the wedding of cellular glass gravel and geocell. Even for the standard house application, the use of geocell will induce extra stability allowing to reduce the thickness of the concrete slab on top of the foamed glass gravel.

 

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