Design and Construction of the Sutong Bridge Foundations-Article

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The Sutong Bridge crosses the lower Yangtze River in China and was designed with a 1,088 m cable-stayed main span and 306 m towers. Its foundations were built in deep water amid strong currents, waves, heavy shipping, and a rapidly changing riverbed. The main pylons stand in water depths of about 30 m and 16 m; soft and sandy sediments extend hundreds of metres below the riverbed.<br /><br />Each pylon is supported by 131 drilled shafts, 2.5 m in diameter and approximately 121–124 m long, capped by a 13.3 m-deep pile cap. Permanent steel casings stabilized the upper portions of the shafts. Because drilling disturbance and debris could reduce end-bearing capacity, the shaft tips were post-grouted to compact the soil and improve performance. Osterberg-cell tests showed that grouting increased measured capacity by about 20%; a test shaft developed 27 MN of end bearing at 44 mm settlement after grouting, compared with 16.5 MN before treatment. Testing also indicated stiffer shaft response near the grouted tips.<br /><br />Scour protection was designed for potentially severe erosion around the pylons. The system combined temporary sand-filled geotextile bags, quarry-run material, and layers of armour stone across inner and outer zones, with a wider “falling apron” intended to settle down into scour as it developed. This robust, flexible approach suited the site’s deep water, strong currents, and limited visibility.<br /><br />The large pile caps were constructed inside double-walled steel caissons lowered into position using strand jacks and controlled flooding. The caissons provided buoyancy, stiffness, a temporary cofferdam, and permanent ship-impact protection. After placement and sealing with tremie concrete, the interiors were dewatered and the caps completed in the dry.<br /><br />The project demonstrated that carefully coordinated design and construction methods—including post-grouting, staged scour protection, and controlled caisson lowering—could deliver reliable foundations under exceptionally challenging conditions.

Keywords

Sutong Bridge

Yangtze River

cable-stayed bridge

drilled shafts

post-grouting

Osterberg-cell tests

scour protection

steel caissons

pile caps

deep water foundations