Determination of 3D Modelling Method of Soil Classes

Abstract

The definitions of the risk factors due to a possible earthquake on the settlement area are useful for decreasing hazard of a potential earthquake and essential for preparing the management plans by the local municipalities and government. Soil amplification, vulnerability of buildings, natural period of soils and liquefaction are the main risk factors of a possible earthquake. On the other hand, before definitions of these risk factors, the distribution of the soil classes should be determined. By the way, the determination of the method of the soil classes in 3D is the main purpose of this study. Detailed geological, geotechnical and geophysical analysis have been performed such as standard penetration test (SPT) and index experiments. Eskisehir has 2 different soil groups known as recent alluvium, and Pleistocene aged old alluvium. Because of the difference in fluvial regime, some or all levels of the old alluvium are eroded and the recent alluvium has been sedimented on the area. Sometimes same soil classes with different alluvium formation could have a boundary in the area and this makes it difficult to determine the formation of the alluvium. Although old alluvium, generally, is a much stiffer formation, some levels of old alluvium have low SPT values. There are three ways to determine the vertical profile of the soil. One is the conventional way, the joining of the same soil classes' boundaries with engineering insight, depending on the law of superposition. The second one is 3D kriging of the soil classes depending on the geologic hierarchy and the third one is the indicator kriging. In this study three methods are performed separately the soil classes, the methods are compared and the most reliable method is defined.