Construction methods · Piers, pylons and abutments

MSE (reinforced soil) abutments

The approach fill itself is turned into a wall with layers of steel strips or geogrid behind precast facing panels, and the deck sits on a small seat on top or on piles through the fill. Cheaper and faster than a concrete wall, tolerant of settlement, and the standard in the game and in most highway practice for fills up to about 12-15 m.

How bridges get built · Piers, pylons and abutments · MSE (reinforced soil) abutments

Also called: mechanically stabilised earth abutment, reinforced earth, GRS abutment

Concept diagram (TheBridgeEng)

How it is done

Cast a levelling pad; erect facing panels row by row, placing and compacting select granular fill in 300-400 mm layers with the reinforcement between.
Build the seat beam on the fill (true abutment) or drive piles through a sleeve before the fill and cast the seat on them (mixed abutment).
Place the approach slab and drainage.

Where it fits

Fills of 4-15 m on competent ground, highway interchanges, sites where formwork and cranes are scarce, seismic regions (ductile).

Where it does not

Soft foundation soils without treatment, aggressive or saline fill (corrosion of steel strips), scour-exposed river banks.

Plant, pace and money

PlantSmall crane or excavator for panels, compaction plant, no formwork.

Productivity1-2 m of wall height per day.

CostUSD 250-450 per m2 of face, roughly half of a concrete wall.

Risks and controls

What goes wrong

Fill of the wrong grading, corrosion of reinforcement in wet or saline fill, panel bulging from poor compaction, seat settlement on a true MSE abutment.

Quality assurance

Fill grading and electrochemical tests, compaction tests per layer, panel alignment survey.

Examples

Highway interchanges worldwide since the 1970s; Gulf highways use them almost exclusively.