Liquefaction analysis of soils in ortahisar district, Trabzon province, based on SPT, CPT, and geophysical study data

Liquefaction is defined as the phenomenon where fine-grained sandy and silty soils, saturated with water, behave like a liquid during earthquake vibrations due to the increase in pore water pressure and the reduction of effective stress to zero. Liquefaction in residential areas can cause various types of deformations in the ground structure and lead to significant damage. The effect of liquefaction is particularly severe in the damage caused by large earthquakes. It occurs in loose sandy and silty soils, where shallow groundwater or soils beneath the sea bed are present, and is induced by the effects of an earthquake. A large part of the study area in the Ortahisar district of Trabzon is located in the sea. Based on SPT and CPT tests conducted in the sea, the geology of the study area consists mainly of silty sand, silty gravelly sand units. Based on SPT and geophysical studies carried out on land, it has been determined that the area is composed of sandy and gravelly units. Due to its location and geology, the study area may face liquefaction risk in the event of an earthquake. This thesis aims to determine the liquefaction potential of the study area using data obtained from various methods. The SPT test has been conducted most frequently in the study area due to its practicality, speed, and cost-effectiveness, and laboratory tests have also provided information about the physical properties of the soil. To make more frequent and precise measurements in the soil, the CPT test has also been utilized. As one moves from the open sea towards the coastline, gravelly units increase, and eventually, andesite/basalt bedrock is encountered. In areas where bedrock is observed, it would be difficult to apply other tests, so seismic refraction – MASW studies, which are suitable for use in all soil types, were conducted in these areas. In this thesis, to determine the liquefaction potential of the land, 30 boreholes were drilled for SPT tests, 10 CPT tests were performed, and seismic refraction – MASW studies were conducted along 8 lines. This study is expected to serve as a guiding resource by highlighting the advantages and disadvantages of the methods used to determine liquefaction potential and their respective application areas.