Bridge Approach Slabs Raised

Bridge Approach Slabs Raised with a Minimum of Fuss

Sinking Bridge Approach Slabs - the causes of the problems

The sinking of bridge abutment slabs is not an uncommon road problem. It is caused by the pounding given to bridge approach slabs particularly by heavy vehicles. Especially the drop of the air bag suspension springs of modern B Double trucks sets up a destructive wave of resonance. 

Typically, the first step is to top up the roadway surface with bitumen to give a smooth ride, but this does not treat the cause of the problem. Topping with bitumen works for a while, but eventually the settlement becomes too bad to be rectified this way any longer. When big, heavy trucks start to bounce on the surface it begins to break up. That’s when modern road authorities call for Uretek.

Bridge Approach Slabs - the Solution

The Uretek Method of raising and stabilising sunken bridge abutment slabs is simple, quick and convenient. Small (16mm) holes are drilled through the slabs at in a grid pattern.  Down through those holes a multi-component structural resin is injected under the slab to variable depths depending on fill conditions.

The resins expand aggressively and first of all fill any voids existing under the slab. Then they squash any ground that can still be compacted. That stabilises the slab and eliminates movement, deflection and vibrations.

As the injection process continues, the resin expansion begins to lift the slab. The lifting is continuously and very carefully monitored by laser levels or other devices, so that the slab and sections of adjacent roadway (if required) are raised to exactly the correct position.

Bridge Approach Slabs - Advantages of Uretek

The URETEK Method also offers a number of other advantages. These are exemplified by the case of the Northbound approach slab of one of the seven bridges on the Hume Highway near Goulburn, NSW, a typical Uretek job:

Kevin J. Kennedy of the Roads and Traffic Authority’s Southern Division called in Uretek when that slab had gone too far to respond satisfactorily to bitumen topping.

The Uretek team of experienced operators went in their self-contained mobile works unit and carried out the slab-raising on a Thursday to avoid any interruption to the heavy weekend traffic. Only one lane was closed off at a time so that constriction of traffic was absolutely minimal.

 The curbside lane (carrying the majority of heavy trucks) had sunk 40 mm and the other lane was down 30 mm. Nevertheless the whole job was completed in just a matter of hours. Traffic was only restricted to one lane and opened up to both lanes just 30 minutes after the last injection.

 Apart from speed and minimising inconvenience, there are two other major advantages offered by this method.  Firstly, the Uretek material will self-seal, preventing any resin escaping or running down the embankment. 

 Secondly, it does not become brittle and break up with future pounding as it has ductile properties.

 Thirdly the URETEK Method is not an unconfined ‘hydraulic’ lift. As lifting is done by expansion of the Uretek resin, fine control of definite areas and levels is usually achieveable.

 All of this contrasts markedly with the old-fashioned practice of injecting concrete slurry under pressure, which is messy & time-consuming and tends to break up with the relentless stress of heavy traffic.

URETEK WARRANTY

URETEK materials injected below concrete have been specifically engineered to resist shrinkage or deterioration causing significant settlement, and as such are warranted by URETEK in strict accordance with the product durability requirements of the applicable Local, State or National Building Code.

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