Driven Iron pile solutions for bridge abutments in Somerset West
GeoPile Africa and Geomechanics have been involved in the founding of two pedestrian bridges which are being built on both North and South sides of the R44 vehicle bridge which crosses the N2 near Somerset Mall in Somerset West.
The 4 piers of the bridges are resting on large concrete bases, but piles were required for each bridge abutment.
Geomechanics conducted Dynamic Penetration Super Heavy (DPSH) tests to accurately estimate the depth of suitable founding material. The tests revealed a variance in bedrock depth of about 2m between the north and south sides; the Southern side is 4m below current road underpass level while it is 6m deep on the northern side.
The depth of fill material above the underpass level was approximately 6m.
Driven ductile iron piles with dimensions of 118mm diam., 7.5mm wall thickness, with 200mm diam. Grouting shoe, were installed with a 35mPa grouted annulus, to give better shear load resistance.
Each pile is driven to practical refusal, using a powerful demolition hammer, which produces around 3000kN per blow, up to 400 blows per minute.
The piles were designed to take safe working loads of 450kN in compression and 30kN in horizontal load.
There was quite a large variance in refusal depth between the two sides of the N2, with the pile length ranging from 12 on the South, and up to 20m for one of the piles closest to the existing vehicular bridge abutment footing.
All 8 piles were installed in just 9 hours on site.