Evaluation of liquefaction potential and post-liquefaction settlements in a coastal region in Atakum

Abstract

Soil liquefaction is one of the most momentous causes of damages induced by earthquakes. It can be described as a sudden decrease in the strength of saturated, cohesionless soil layers, remaining effectual for a length of time under transient and cyclic loading due to excess pore water pressure generation. Consequently, the most appropriate and typical soil condition which brings the potential out to liquefy is loose sand with a groundwater table close to ground surface. This study is pertinent to determine the liquefaction potential in a coastal region in Atakum County of Samsun Province, Turkey. Therefore, empirical equations were used to determine the peak ground accelerations for three scenario earthquakes with the magnitudes of 6.5, 7.0, and 7.2 in order to consider in the simplified procedure context proposed by Seed and Idriss (J. Soil Mech. Found. Div. ASCE 97: 1249-1273 1971). Liquefaction potential evaluations were performed using standard penetration test blow counts for four boreholes for sandy portions of the soil profile which exist in the first 20 m below ground surface. In addition to analytical evaluations, two-dimensional nonlinear analyses were ran with Towhata-Iai constitutive model suitable for liquefaction analysis available in DIANA finite element software to clarify excess pore pressure generation that leads to liquefaction. It is also well-known that sands tend to densify when subjected to seismic shaking. Densification of undersoil causes settlement at the ground surface. Liquefaction induced settlements usually cause damages on both superstructures and infrastructures. On the basis of this fact, the method proposed by Ishihara and Yoshimine (Soils Found. 32: 173-188 1992) was used to determine the settlements for scenario earthquakes.