Insight to Foundation Construction of Extradosed - 3rd Narmada Bridge over River Narmada, Bharuch, Gujarat-Paper

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The paper describes the foundation design and construction of the third Narmada Bridge at Bharuch, Gujarat, a four-lane, 1,344 m bridge with 132 piles, each 1.5 m in diameter and about 50 m deep. Its foundations were built in an intertidal river environment with daily water-level changes of at least 3 m, variable ground conditions, and pile caps that needed to be cast dry.<br /><br />For the deep-water foundations, the team designed rectangular cofferdams using circular steel liners and sheet piles, supported by a single strut-and-waler bracing level. WALLAP and STAAD analyses assessed the cofferdams under staged construction loads. At the most demanding location, P2, deep dewatering would have caused high wall bending forces and required another bracing level. Instead, controlled backfilling inside the cofferdam counteracted water pressure, reducing the critical bending moment by 35% and avoiding additional struts. Backfilling was also used at P1 and P3.<br /><br />Construction involved a spud barge and piling rig for the permanent piles, followed by installation of the cofferdam walls using a guide frame and vibratory hammer. After sealing and dewatering, crews placed a concrete working layer, prepared the pile caps, and cast them in dry conditions. Jute-threaded grout seals helped reduce leakage at joints between circular liners. At the shore-edge P4 foundation, a protected island and dewatering system made a cofferdam unnecessary.<br /><br />The cofferdams also provided a safe work area for constructing the lower pylons and pier tables, after which the temporary walls were removed. Despite localized leakage, the system performed reliably with no significant deflection. The project demonstrates how staged analysis, controlled backfill, and practical use of available materials can make complex foundations in tidal waters safer and more economical.

Keywords

Narmada Bridge

foundation design

cofferdam

deep foundations

intertidal river

pile caps

controlled backfilling

dewatering

pile construction

Bharuch Gujarat