SOLMAX Written

Written

Course Information
When retaining walls are needed on a project, there are several options available. For fill walls, the best options are concrete gravity walls or mechanically stabilized earth (MSE) walls. Geosynthetic (geogrid) MSE walls offer several advantages over traditional concrete gravity walls and metallic-reinforced MSE walls, making them a popular choice for owners and engineers. Geogrid MSE walls are roughly one half the cost of concrete gravity walls, depending on the size and height of the wall.

The cost-effectiveness of geogrid MSE walls in comparison to metallic reinforcement is due to the restrictions on the gradation and the pH of the backfill gravel that must be used to prevent the corrosion of metallic reinforcement. Geogrid MSE walls can utilize onsite soils for reinforced backfill (if it meets the gradation and plasticity requirements), which helps to balance the cut and fill for the project, reduce the need for high-quality import fill, and reduce transportation costs while minimizing the environmental impact associated with sourcing and transporting materials. Another benefit of MSE walls is they can be designed to incorporate vegetation, enhancing biodiversity and creating a more aesthetically pleasing environment.

Author
Laura Spencer, Ph.D., P.E.

Learning Objectives
At the conclusion of this article, the reader should be able to understand the following:

• The advantages of MSE walls and of using geosynthetic (geogrid) reinforcement.

• How different polymer geogrids have different properties and how that affects the long-term design strength.

• How to calculate the long-term design strength (LTDS)

• The different design methodologies currently acceptable by AASHTO/FHWA and NCMA.