Mapping geotechnical data by GIS: a case study of Elazig city, Turkey

Elazig city has suffered from the effects of several strong earthquakes. Therefore, it has required to understand the ground conditions of Elazig for a successful urban planning, design and construction of new structures. Geological, seismic, hydrogeological and geotechnical properties are considered as the most crucial factors. Depending on the location of each structure, impact of these factors could have a different effect. To understand the effect of geotechnical factors of the soil underlying the site, subsoil exploration was examined. The main goal of the thesis was primarily to generate geotechnical maps, which saves especially the cost of soil investigations, time, and provide a quick source of information for engineering projects. Geotechnical maps are widespread nowadays due to the existence of Geographical Information Systems (GIS). The maps in this study were generated by ArcGIS software using Inverse Distance Weighted (IDW) method. In this study, 210 borehole samples were collected to determine the index properties and soil classification for the subsequent allowable bearing capacity evaluation. Furthermore, groundwater level, water content, shear wave velocity, compressional wave velocity, soil amplification and soil classification calculations and maps according to Turkish, NEHRP and EUROCODE 8 were generated. According to borehole analysis until 15m depth, groundwater could not be seen much and might be at deeper levels. Due this reason liquefaction analysis had not been made. Bearing capacity analysis based on SPT-N have shown that the results of Terzaghi & Peck and Meyerhof methods were close to each other. The compressional wave velocity values were higher than the shear wave velocity values in the study area. As a result of geophysical data`s, the soil classification presented that the study area was C (low hazard) according to Turkish earthquake regulations, B and C according NEHRP and A and B according to EUROCODE8. In addition, these maps will help in preliminary studies, feasibility studies, land use policy, design of urban planning for further studies and can represent the distribution of different geotechnical properties in an accurate easy to use manner.