DETERMINATION OF 3D MODELLING METHOD OF SOIL CLASSES

11th International Multidisciplinary Scientific GeoConference SGEM2011, www.sgem.org, SGEM2011 Conference Proceedings/ ISSN 1314-2704, June 20-25, 2011, Vol. 1, 413-420 pp

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. Eskişehir 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.

Keywords: soil classification, 3d modeling of soil, 3d kriging, indicator kriging