Determination of earthquake design spectrum of improved soils

'EARTHQUAKE' is the shaking of the earth's surface by sudden waves caused by cracks in the earth's crust. Depending on the map spectral acceleration coefficients and local soil impact coefficients, earthquake ground motion spectra are generated using standard or site-specific earthquake hazard analyses. Site-specific soil behaviour analyses are performed to determine the variation of earthquake ground motion in the bedrock through the soil layers and the earthquake ground motion at the ground surface. In this study, in order to observe the change in the design spectrum curve, the finite element method was used and numerical modelling was performed on natural ground, ground with building load and ground with jet-grout columns using the UBC3D-PLM model to observe liquefaction in a ground with liquefaction potential in PLAXIS programme. The behaviour of the identified soil profile when earthquake load is applied is modelled in the numerical model to give realistic results. The model created is a 200 m wide and 30 m high sand soil profile with high liquefaction probability. Jet grout columns with a diameter of 80 cm and a length of 15 m were defined in the model. The earthquake data to be affected on the soil profile were taken from the PEER database. The model was scaled according to the target spectrum in SEISMOMATCH programme according to the design spectrum curve obtained from AFAD for ZD soil class. The model was modelled statically and dynamically in separate stages as natural soil and improved soil. Analyses were carried out for 11 earthquakes at the points determined in the cross section and the accelerationtime change on the surface and the change in the design spectrum graph were observed. The results obtained from the analyses are similar to the earthquake motion results, however, it is observed that there is an increasing trend at the points located below the improvement from the determined analysis points and a decreasing trend at the points located in the improvement area.