Investigation of liquefaction potential of soils with numerical analysis methods, case study

Turkey's location within a significant earthquake belt entails risks such as reduced bearing capacity and deformations in soils. One of the most critical and complex of these risks is earthquake-induced liquefaction. The significance of liquefaction, particularly highlighted after the 1999 earthquake, occurs during seismic events in loose sandy, silty soils and areas with shallow groundwater, leading to severe structural damage. The mechanism of liquefaction is explained by seismic waves generating shear forces in undrained, saturated, and loose soils during an earthquake, causing the displacement of soil particles. The inability of water to drain due to sudden and short-duration movements leads to an abrupt increase in pore water pressure. This pressure increase eliminates the contact forces holding the particles together, causing the soil to lose its strength and behave like a liquid. Liquefaction in soil layers during an earthquake alters the soil's stiffness and strength, creating severe adverse effects on engineering structures. Its most significant consequences include structural damages such as loss of foundation bearing capacity, excessive settlements, lateral spreading, and slope failures. This situation makes liquefaction a risk of great importance from an engineering perspective. Consequently, it is of vital importance to perform liquefaction calculations using experimental formulas and empirical correlations derived from field, laboratory, and seismic parameters to determine the liquefaction potential in sandy and silty soils during an earthquake. Liquefaction hazard analyses require the examination of conditions such as earthquake magnitude, distance from the epicenter, soil composition, and density state. In this thesis, liquefaction calculations will be performed using SPT (Standard Penetration Test) and Shear Wave Velocity (Vs) methods; furthermore, the static and dynamic behaviors of an area subjected to liquefaction will be analyzed using the finite element method (Plaxis 2D program) to evaluate the changes in settlements before and after ground improvement.