OasisLMS

Abstract: Reservoir across Volta River located at Ghana, West Africa is one of the largest man-made waterbody in the world, measured in terms of area. Volta lake, being man-made, the variation in overburden sand was significant. The design & construction of this 300m long single standard gauge railway bridge was never an easier task. Volta bridge was designed as 5-span simply supported structures between the abutments with a span length of 60m each. Earlier, 2.0m diameter vertical piles were planned for foundations, given the fact that the peak ground acceleration (PGA) was 0.16g. Due to change in PGA from 0.16g to 0.35g, piling philosophies had to undergo a complete revamping to mitigate such large seismic lateral forces, and Raker pile options found to be optimal.

Raker pile at Volta Bridge is one such unique system in the country of Ghana, and Authors’ firm have designed & constructed one of such deepest RCC Bored Cast-In-Situ Raker Pile in the world. For this deep gorge of Volta River, with a maximum water depth of 31m, liner length requirement for the longest pile was 65m till the rock touch levels. The maximum length of pile executed was 76.5m including its length of socketing into hard rock.

Given a choice, bridging such deep gorges could have been with long span structures abutting the river banks like Balance cantilever, Arch bridge, Cable stayed bridge, etc. As the geometry of the adjoining approaches were finalized, any alteration to the alignment would have led to design & construction delays making a non-feasible soultion. Design validation had to be done during construction stage of every pile in the group before concreting. Post construction, the Pile group performance was demonstrated by instrumented lateral load test.

The Volta bridge now stands completed and is an epitome of design & construction challenges.

Keywords: Raker Pile, Deepest Pile, Volta

Mr. NAVEEN GOVINDARAJU; Mr. Udaiveer Singh

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