A GIS model for preliminary hazard assessment of swelling clays, a case study in Harran plain (SE Turkey)

Swelling behavior of clayey soils regarded as a hidden disaster, causes a great deal of damage in light hydraulic structures such as drinking water network, irrigation pipes or open canal linings through which water can easily leak and penetrate into soil during loading and unloading stages. Early identification during site investigation and laboratory testing is extremely important to ensure that the appropriate design strategy is adopted. The clay soils having swelling potential are generally found in arid and semi-arid regions, such as in the Şanlıurfa-Harran plain located in the southeast of Turkey. The problems associated with swelling clays occurred for the lightweight hydraulic structures constructed in Turkey have been met during the construction of irrigation structures in the scope of Southeast Anatolian Project as the Turkey’s greatest water resources project. Therefore, the identification of such soils and the assessment of their swelling potential parameters are necessary for hazard mitigation planning and land-use management. In this scope, extensive geotechnical study is executed for an investigation area. The samples were obtained from the Harran plain where many irrigation canal structures are constructed, and geotechnical study was performed on these samples. Atterberg limit tests often provide the basic field information to substantiate the soil’s swelling nature. The plasticity index (PI) and liquid limit (LL) values are also used extensively for classifying swelling soil and should always be determined during preliminary investigations. Because of this, LL and PI are assessed by using geographical information system (GIS)-based computer software, and LL and PI contour maps are created. Swelling percentages of the soil samples were carried out on both undisturbed and compacted soil samples by using direct methods. As a result of this extensive study, the values of swelling percentages determined for each location are used to obtain the swelling potential hazard map of the area by means of a GIS program. The results of GIS analyses for this area indicate that the analyses based on a lot of data introduce meaningful results for this study. It is expected that these maps will be a useful tool for planners and engineers in their efforts to achieve better land-use planning and to decide necessary remedial measures.