Dunkeswell Bridge, Devon is an old stone built bridge which has become structurally unstable caused by the increased weight and traffic of this small arch based bridge. Unfortunately the road was closed until all works had been completed, the contract had to be finished in a short time, scale safely and without causing further damage to the bridge while it was being used as a work platform.
Scope of works:
*Install 12 No. 273mm dia Steel Cased Bottom Driven Piles to a designed set.
*Insert 12 No. 150mm dia 6mm walled steel Reinforcement.
*Concrete all piles to top of capping beam.
*Leave one chosen Pile up 500m from CSL to be tested by request of main contractor.
The road to Dunkeswell in closed untill all works are complete, by main contractor South West Highways allowing only pedestrians and cyclists safe passage. Which is why barriers and welding screens were used to prevent harm to the public.
The arch of the bridge is supported temporarily, while work goes ahead on top. And once the slab is cast over the piles the load will be transferred to them via the capping beam. Leaving the stone arch and sides of the bridge untouched.
The D1000H with built in hydraulic welder, and out riggers make for a very safe machine while operating over an excavated pile position.
All 12 piles installed to design depth, some of the driven piles had to be moved due services running under the road surface. The piles either side of the bridge, as they were being driven displaced the ground and put pressure on the sides this was also taken into account by moving them inwards.
A 150mm dia steel tube with a 6mm thick wall was inserted into each completed pile. Special skid spacers were welded to the sides of the reinforcement tube giving the correct concrete cover.The reinforcement goes top to bottom and is left 500mm below CSL which is top of capping beam, the piles were then filled with high slump, high strength concrete.
No pictures were taken of finished piles as heavy showers in the afternoon caused flash floods resulting in the road turning into a river which consequently ended in a number of piles filling with water, these were pumped out and were then ready for concreting.
3 Bedroom mid terrace house in Weston-Super-Mare,
with subsidence to the front and rear of the property. The house is positioned between a block of 5 flats and another 3 bedroom house, and on removal of the plasterboard inside it was found that the property was built with no cavity on the party wall adjacent to the flats. Both party walls are built off piled beams and the front and rear of property is built off standard footings.
Externally there are major cracks to front and rear of the brickwork and internally the aerated concrete blocks are all loose and cracked on both the first and second floor of the house.
Scope of works:
*Remove reinforced concrete floors and excavated down to bottom of slab before Piling work commences.
*Resin bond all cracks with Heli bar.
*Mobilise T5000 Rotary Bored Auger Rig which will bore 250mm dia to 5.0m reducing vibration and taking us past any obstructions before Driven Piling starts.
*Demobilise T5000 and mobilise D500 Piling Rig to drive 17 No 220 Steel Cased Bottom Driven Cast Insitu Piles.
*Demobilise D500 and concrete all Piles with reinforcement.
*Break out needles in walls front and back.
*Fabricate 250mm reinforced concrete slab.
*Remove jacks for total isolation and clear site.
While removing the reinforced concrete floors we found that the footings at the rear of the house were found to be a lot wider than anticipated and 2 Piles were redesigned and placed outside.
With all 17 No. 220 Steel Cased Bottom Driven Piles, installed to designed depth and concreted, the underside of the reinforced concrete slab is blinded ready for laying out the steel reinforcement. As there is no Heave involved in this job just insufficient footings, we are not using any void forming collapsible materials and no Anti Heave Sleeve around our Piles (Which where there is Heave involved allows the top stratum of clay to move with the changing variables of weather).
The Reinforced steel slab has been fabricated insitu and 500 x 250 needle beams have been inserted into the walls, picking up the front and rear walls and preventing them from sinking by transferring the load through the entire 250mm deep Reinforced concrete slab.
We have a H12 top and bottom mat with H16 bar’s running side by side and top and bottom around all Piles locations. The project is now ready for concreting.
All concreted and job finished.