Mechanically stabilized earth (MSE) walls have replaced traditional concrete retaining walls over the last 20 years providing a way to create earth retaining walls. Mechanically stabilized earth walls have plenty of advantages when compared to conventional reinforced concrete walls mostly because they are installed easily and because of the time it takes to assemble these walls. These walls consist of granular soil used as backfill, reinforcing mesh or strips, and a precast concrete block that will be assembled on top of each other forming an interlocking gravity earth retaining wall. MSE walls can be used to create high, curved or shaped walls that are ideal when a lot of utilities are in the area and there is no option to bring heavy equipment to the area.
Applications of Mechanically Stabilized Earth Walls
The selection of mechanically stabilized earth walls will vary from one site to another but can be used in these situations:
- As temporary structures for highway projects
- Use as soil retention structures or dikes
- As containment structures around oil tanks
- Containment structures around gas storage tanks
- Dams constructions and levees additional height increase capacity
- For creating storage areas
- At construction sites with poor soil conditions
- On areas of high seismic activity.
- Bridge Abutments
- On wing walls
Things to Consider When Building an MSE Wall
If you are planning to use one of these earth retention systems, you will need to take care of the following aspects:
- Verify the foundation is properly compacted and leveled
- Inspect panel and soil reinforcement prior to placement
- Make sure the soil used for backfill has been approved and tested
- Fill lifts shall be about 6" thick
- Use corner panels at all corners
- Verify the batter of the panels often and adjust as needed
- Do not excavate in front of the wall once it has started construction
- Never cut soil-geotextile to avoid obstructions such as storm drainage systems without approval
- A one-half inch expansion joint is recommended between different materials of cast-in-place concrete
Benefits Of Using MSE Earth Retaining Walls
Contractors and builders tend to choose these types of systems due to their great economic and constructive benefits. Some of them are:
- Simple construction.
- The use of heavy equipment is reduced.
- More land is available for construction.
- Faster construction than traditional concrete walls.
- Do not require specialized labor.
- Reduces the need for wall finishing.
- Less site prep is needed.
- Can be built in confined areas or areas where a concrete wall is almost impossible to be constructed.
- Reduces the need for the land acquisition process.
- Mechanically Stabilized Earth walls are susceptible to elastic deformation.
- High seismic load resistance.
- MSE walls can be used as tall structures, exceeding more than 60 feet of wall height.
- Can be combined with other products.
- Various shapes and forms can be made.
- Excavation works for footings are reduced.
- Can be built in poor soil areas.
MSE Earth Retaining Wall Facing Types
There are several facing systems used with mechanically stabilized earth systems. Below is a list of most common facing options:
- Segmental precast concrete panels: Precast panels in the form of square, rectangle, diamond or hexagon, connected with shear pins.
- Modular block wall: Solid or with cores filled with aggregates during their installation. Usually name Keystone®, Versa-Lok®, etc.
- Metallic Facings: lighter facing finished, made of galvanized steel split into half cylinders.
- Gabion Facing: can be connected to the wall systems.
- Geosynthetic Facing: Geotextile reinforcement, forming the face of the retaining wall. They can be exposed to vandalism, weather inclemency and other types of surfacing problems.
- Post-construction Facing: Shot Crete, cast-in-place, spray on, plastering or other techniques can also be used as a compliment facing for the mechanically stabilized earth wall facing. It adds some cost to the construction but will provide an aesthetic finish surface for the MSE walls.