Mechanical Stabilization of Subgrades and Bases Case History

Photograph of a excavator buried in mud — Photograph of an excavator buried in muck.

Project Summary/Scope:

Extremely weak soils (CBR <0.5%) were encountered during construction of a highway embankment. Additionally, the subgrade soils consisted of saturated silty clay with a high water table. Designs consisting of 42”+ of imported material with multiple layers of geosynthetics and geogrids were proposed.

Engineers used Tensar+ design software to produce a design consisting of 35” of clean sand placed overtop of one layer of Tensar® InterAx™ geogrid. This solution allowed the use of on-site borrow material that was more economical.

Complementary Technologies Used: N/A

Alternate Technologies: Over-excavation of the subgrade and replacement with aggregate was considered however the project site was located a long distance from a high-quality aggregate source. The large amount of required material and hauling costs were extremely high.

Photograph of rolling out geogrid on subgrade. — Rolling out geogrid on subgrade.

Performance Monitoring: N/A

Cost Information: The customer received a substantial cost savings by not importing aggregate from far off-site. Total savings numbered several millions of dollars.

Case History Author/Submitter: Nick Nuttbrock, Tensar Regional Manager, SD/NE/IA; nnuttbrock@tensarcorp.com

Project Technical Paper: N/A

Date Case History Prepared: December 2021

Final placement of materials on roadbed. — Final placement of fill materials on expanded roadway.

Case History Prepared By: Katie Phillips

Title

Highway Embankment Stabilization using Multi-axial Geogrid

Location

Angora, Nebraska

Year

2021

Technology

Mechanical Stabilization of Subgrades and Bases

Owner

Nebraska Department of Transportation

Contractor

IHC Scott

Engineer

Nebraska Department of Transportation