A shear modulus degradation model considering pore water pressure increases and liquefaction

In recent years, the importance of the subject has increased due to the increase in liquefaction-induced structural damage in earthquakes. Hence, numerical analyses considering structure-soil interaction to determine liquefaction settlements have become popular. Besides the Turkish Building Earthquake Code has made soil behavior analyses mandatory for construction on liquefiable soils. In both liquefaction analyses and soil behavior analyses, the shear modulus reduction curve, which determines the dynamic behavior of the soil, is one of the most important inputs. The reduction of shear modulus in sands (coarse-grained soils) depends on the average effective stress, void ratio, relative density and uniformity coefficient. It is necessary to add the deformation rate to these parameters. In this thesis, it is shown that additional increases in pore water pressure during liquefaction can cause shear modulus reduction and liquefaction-induced deformations that may be initiated by an increase in pore water pressure during dynamic (repeated) loading in sands (coarse-grained soils) are included in the shear modulus reduction relationship. In order to find the shear deformation value (tv) at which the additional modulus reduction starts, a database was created and a new equation based on the effective stress, void ratio, relative density and uniformity coefficient was proposed. Thus, depending on the type, stiffness and stress level of the submerged sands, a modulus reduction curve that takes liquefaction into account is developed. The one-dimensional soil behavior analyses performed at the end of the thesis show that the developed model is simple but effective/successful.