Countermeasures against Soil Liquefaction at Galataport Project in Istanbul, Turkey-Paper

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The paper describes the Multi-Purpose Bottom Plug (MPBP), developed for deep basement excavation at the Galataport project in Karaköy, Istanbul. The site contains thick, loose fill and liquefiable marine sand, with groundwater and high seismic risk, as well as nearby historic buildings requiring protection.<br /><br />The MPBP combines three functions: groundwater seepage control, liquefaction mitigation and structural resistance to uplift. Overlapping, double-fluid jet-grouted columns form a hydraulic bottom plug. Above it, pseudo-elliptical jet-grouted columns create a stiff lattice intended to limit soil deformation and pore-pressure buildup during earthquakes; these columns also support the future building. Permanent, double-corrosion-protected micropiles installed within the treated columns resist uplift.<br /><br />A nonlinear, three-dimensional time-history analysis using the 1999 İzmit earthquake record informed the lattice design. Results indicated that the selected 7-by-7-m grid substantially reduced liquefaction potential. Field trials and quality checks confirmed treated-soil strength and stiffness targets, column widths exceeding 4 m, and continuous overlap. A static tension test reached 2,000 kN, supporting the design assumption of approximately 400 kPa micropile-to-grout skin friction.<br /><br />Electronic systems monitored drilling position and jetting operations, helping ensure column overlap and that micropiles were installed within the treated ground. The authors emphasize that successful delivery depended on combining advanced analysis, specialized jet-grouting technology, precise electronic controls, extensive monitoring and experienced personnel. The project demonstrates that wide pseudo-elliptical jet-grouted columns can serve as both liquefaction-mitigation and structural elements when ground conditions are suitable.

Keywords

Multi-Purpose Bottom Plug

MPBP

jet grouting

liquefaction mitigation

groundwater seepage control

uplift resistance

micropiles

deep excavation

seismic risk

Istanbul Galataport