Cost effective cast-in-place Foundation for Big Qualicum River Bridge
Big Qualicum River Bridge is the largest span bridge of the Vancouver Island highway system, connecting the provincial capital of Victoria with the northern parts of the island. The difficult terrain and limited site access of this four-lane bridge with a 144 m center span made conventional piling expensive and was a concern for the environment.
The project engineers chose GEWI® piles for the twin parallel arch abutment foundations because of many advantages:
Small versatile drilling equipment used for the pile installation eliminated the need for expensive access roads and large piling platforms required for conventional systems.
Small equipment reduced the environmental impact of construction work. All GEWI® piles are free of harmful substances.
The bridge is located in one of Canada's most active seismic zones. The performance of GEWI®piles in both tension and compression makes them ideal for resisting an earthquake.
200 piles of Ø 57 mm DYWIDAG GEWI® threadbar (average length 12 m) with double corrosion protection (DCP) were installed at even spacing under the four arch abutments (50 piles per footing). Pile spacing at the pile head was approximately 60 cm with pile inclinations ranging from 38' to 48' off horizontal. The soil consisted of a sand/gravel mixture, interspersed with cobbles and boulders, into which the 230 mm cased boreholes were drilled using a Krupp double head rotary drill with reverse hammer action.
An extensive field-testing program was conducted prior to production. The testing involved several short GEWI® piles in tension and two full-scale strain gauge instrumented pile load test in compression. In order to simulate actual conditions, a pile set at 45' was tested in both tension and compression. Test results demonstrated the high capacity of GEWI® piles: in compression more than 2,200 kN were achieved (exceeding the GUTS* of the bar!). The failure occurred as the top portion started to buckle. The design load was 1,200 kN.
* GUTS - Guaranteed Ultimate Tensile Strength