Assessment of Soil Liquefaction Potential in the Coastal Area of Bushehr Using SPT Data

Liquefaction is a critical hazard in seismically active coastal zones, where saturated loose soils may lose strength during earthquakes. This study assesses the liquefaction potential in the Bushehr coastal area (Persian Gulf, Iran) using the simplified cyclic stress method and SPT data from seven boreholes (۱۵-۳۰ m depth), supported by laboratory tests including grain size distribution, Atterberg limits, and natural water content. Fine-grained soils observed in the upper ۰-۱۰ m were classified as non-liquefiable based on Bray & Sancio (۲۰۰۶) criteria, mainly due to low water content. In contrast, liquefiable sandy layers were consistently found between ۱۰ and ۳۰ m depth. Although these deeper sand layers have high liquefaction potential, their burial beneath thick cohesive soils significantly reduces the risk of surface manifestation. Exceptions exist in zones with surface or shallow sand layers, particularly BH-۲, where the Liquefaction Potential Index (PL) indicated a moderate-to-high risk. Additionally, one ML layer exhibited boiling and deformation due to high upward hydraulic gradients during excavation below the groundwater level, mimicking liquefaction despite not meeting standard criteria. The study recommends that geotechnical designs consider both the presence of deep liquefiable layers and changes in overlying non-liquefiable soils due to excavation. Attention is also advised for silty soils and areas with exposed sands to ensure seismic safety in future developments.

کلیدواژه ها:

Problematic soils ، Cyclic stress method ، Standard Penetration Test (SPT) ، Liquefiable soils ، Persian Gulf coastal areas