A Moisture Index Map of TURKEY for Design of Slabs Resting on Expansive Soils by GIS Approach

Abstract

Expansive soils commonly exist in the arid and semi-arid regions of the world. Climate changes depending on these soils moisture content variation and this causes large volume changes. Although there are some methods developed for use in design of slabs resting on expansive soils, project planning information is needed locally in regions where this type of soil exists. The most important one of this knowledge is moisture index. For this purpose, many moisture index calculations are given in literature. In this study, to calculate Thornthwaite Moisture Index (TMI) described by Thornthwaite (1948), rainfall and temperature records for an average period of sixty-three years of 81 stations of Turkey were received from General Directorate of Meteorology. Later TMI values belonging to each station are calculated by arranging these values in tables. As a result of this comprehensive study, the values of TMI determined for each station are used to design slabs resting on expansive soil and TMI map of the area by using Geostatistical Analyst Module of ArcGIS 10.0 software and Kriging interpolation method. The results of Geographic Information System (GIS) analyses for this area point out that the analyses based on a lot of data introduce meaningful results for this study. The study provides climate of region, soil parameters related to structure to be taken into account in design of slabs resting on expansive soils and a reference is put forward for utilization of geotechnical engineers working in practice.