Ndaiga Bridge, CFA and Pile Testing, August 2015
Scope of Services:
Design and installation of 54 working piles and 1 test pile. Load test to 250T. Integrity test on all piles.
Location: Jinja-Malaba Rd, Uganda
Completion Date: August 2015
Main contractor: Terrain Services Ltd.
Client: Uganda National Roads Authority. (UNRA)
Project Description:
EAP undertook an expedited design build contract as part of the emergency bridge replacement at Ndaiga on the Jinja-Malaba rd. After establishing that Continuous Flight Auger (CFA) piling would be the most efficient method, EAP completed the entire design and build process inside 2 months.
The original bridge on one of Uganda’s most important highways had suffered a failure in one abutment and required replacing as a matter of urgency. EAP’s designer confirmed the preliminary design of 18 piles under each structure was appropriate, and given the limited geotechnical data available specified refusal criteria rather than length. Drilling to refusal reduces slightly the efficiency of the CFA method but gives extremely solid end bearing for the piles.
EAP designed a CFA appropriate concrete mix using locally available materials and specialist admixtures which were then batched onsite by EAP using three carmix self-loading mobile mixers. CFA piling requires concrete with high and extended workability to facilitate pumping and cage insertion. Reinforcement cages were tied on site.
Concrete was batched on site by EAP using three carmix self-loading mobile batch mixers. Concrete mix was designed by EAP specifically for CFA piling. CFA piling requires concrete with high and extended workability to facilitate pumping and cage insertion. Reinforcement cages were tied on site.
During the installation of the working piles a test pile was installed in order to verify the insitu load capacity of the piles. Eight anchor piles were installed around the test pile to provide the necessary reaction and the pile was then loaded to twice the working load of 1234kN. At working load the deflection was measured as 2.5mm and at twice the working load 6mm. Following standard EAP practice every working pile was then integrity tested with a 100% pass rate.
