A performance-based ground improvement solution was developed to enhance foundation support and mitigate liquefaction risks, supported by rigorous testing to validate compliance with project design criteria for the two SC facilities sites.
The project
The Synchronous condensers (SC) are essential for the integration of renewable energy sources into 380kV substations. The SC units at Haden and Yanbu aim to improve voltage profile, frequency fluctuation support, system inertia and short circuit power, ensuring a stable power supply for renewable energy integration.
The challenge
The sites, located 350 km apart, exhibited variable soil conditions consisting of loose to medium dense sands with silt and gravel overlying dense silty sands. The project required compliance with stringent settlement and differential tilt limits by ground improvement to achieve specified shear wave velocity criteria, and liquefaction mitigation to meet the seismic design requirements for a PGA of 0.089g (Site Class C).
The solution
Keller designed 0.8 m RI columns for the critical SC units and 1.15 m Vibro- Stone Columns for the auxiliary facilities. The solution was validated through 300 kPa zone load tests and cross-hole seismic testing to confirm treatment depths of RI columns by achievement of the required shear wave velocity targets.
