Israel and Idaho: Peas in a pod?
Swelling clay of Elephant Butte meets its match
What do Idaho and Israel have in common? Besides sharing two of the the same vowels, not a lot, but they do share one commonality – they are the only two places on earth to use Geocells to combat an issue with swelling clay beneath a roadbed.
The swelling clay was on a stretch of US-95, just south of the Marsing Port of Entry in Owyhee County. Geocells were used on top of existing lime-treated subbase, 3.5' structural section. Central Paving completed the $2.5 million pro
ject for ITD.
"Geocells are typically used for erosion control on the ground's surface, so it was a new experience for ITD, the contractor, and the manufacturers of the materials," explained ITD District 3 Project Manager Michael Van Lydegraf.
Van Lydegraf said this was the first time a fix like this had been attempted in Idaho, and to his knowledge, only the second time worldwide (the first being in Israel).
The project began in late July 2018 and finished in the first week of November. Crews excavated the top 3.5 feet of a two-mile, badly damaged stretch of highway, and a composite mat of "geocells" filled with aggregate was installed at the bottom of the road section. The mat was installed to prevent asphalt damage and bumps in the road by distributing points of localized swelling from the underlying clay across a wider area.
A two-phase research project was conducted by Boise State University and sponsored by ITD to determine how expanding soils would impact the road and to identify solutions to address those impacts. The use of Geocells came from that research.
The study showed there were spots within the rebuilt section that experienced up to seven inches of swelling. The study also showed that the clay really attracted water (a very bad mix), and that rather than fight the water, crews should work with the water to minimize impacts. They decided that rather than eliminating heaving, they would instead try to dissipate it and neutralize the damaging effects.
Now that the project has finished, D3's survey crew will monitor any resulting elevation changes. Early public response to the fix is positive.
Published 03-08-19