Bi-Directional Testing Using Super Cells for the Jiaxing-Shaoxing River Crossing Bridge-Paper

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The paper reports bi-directional static load testing of a sacrificial drilled shaft built for China’s Jiaxing–Shaoxing River Crossing Bridge. The shaft was 3.8 m in diameter and approximately 110.6 m long, and was tested using Super Cells—open-shaped hydraulic devices designed to transfer high axial loads through the shaft while operating at relatively low pressure.<br /><br />Two multiple-cell Super Cell assemblies were installed at different depths. Instrumentation, including embedded strain gauges, telltale rods, and displacement transducers, measured shaft movement and load transfer. The lower device tested the shaft’s lower section before and after tip post-grouting; the upper device tested the middle and upper sections.<br /><br />The lower-section tests reached the maximum planned loads of 70,000 kN before grouting and 84,000 kN after grouting. Post-grouting increased the lower section’s ultimate resistance by about 9.2%. Testing with the upper device also mobilized the middle section’s side resistance, while testing of the uppermost section was stopped after rapid displacement developed.<br /><br />The shaft’s total computed axial resistance was approximately 329,600 kN without grouting and 347,100 kN after tip post-grouting, an increase of about 5.3%. The ungrouted shaft’s resistance was more than five times the estimated design resistance for a shaft founded in weathered sandstone. The tests also showed that resistance varied by soil layer, with pebble and sandstone layers contributing substantially.<br /><br />The authors conclude that Super Cells enabled large-scale load testing and evaluation of shaft behavior across multiple sections. The results validated the shaft’s high capacity and showed a modest overall benefit from tip post-grouting.

Keywords

static load testing

drilled shaft

Super Cell

axial resistance

post-grouting

pile foundation

load transfer

instrumentation

weathered sandstone

bridge foundation