Site Specific Study for Foundation Design of Iswar Gupta Bridge-Paper

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The study evaluates foundation design conditions for the proposed extradosed cable-stayed bridge over the Hooghly River, near the seismically active Eocene Hinge Zone. Geotechnical data from four sites—Baropara, Bansberia ROB, Ishwar Gupta Bridge and Saraswati River—were used to characterize soil profiles and assess seismic response, liquefaction potential and pile performance.<br /><br />Site-response analyses produced site-specific seismic zone factors of 0.195–0.20g, higher than the 0.16g value specified for Zone III in IS 1893:2002. Liquefaction and cyclic-failure assessments found susceptible loose silty sand at Bansberia, from 4–7 m depth, and Saraswati River, from 5–8 m. Baropara and Ishwar Gupta Bridge were not identified as susceptible.<br /><br />Lateral pile capacity was evaluated using a nonlinear Winkler-spring model and IS 2911-2010. The Winkler method generally estimated higher capacities than the code-based method. For 1.0 m and 1.2 m piles, accounting for liquefaction reduced estimated capacities at Bansberia from 262 to 175 kN and from 392 to 282 kN, respectively. At Saraswati River, capacities fell from 262 to 192 kN and from 393 to 305 kN.<br /><br />The findings emphasize the importance of site-specific seismic design and of accounting for liquefiable soil layers when determining pile resistance.

Keywords

extradosed bridge

Hooghly River

foundation design

geotechnical investigation

seismic response

liquefaction potential

pile performance

Winkler-spring model

site-specific seismic design

liquefiable soil layers