2.1.1 Soil
The used soil in this study was obtained from a site, namely Barika soil, situated in Sulaimani governorate, northern Iraq. The studied natural soil is collected at a depth of 0.5 to 1 m from the natural ground level, and is normally consolidated clay. The undisturbed and disturbed soil sample were excavated, placed in plastic bags, and transported to the geotechnical laboratory for testing. Geotechnical laboratory tests were performed on the soil to determine its geotechnical properties. The obtained clayey soil sample was light brown in color, and is composed of some clay. It can be defined as low plasticity soil according to the Unified Soil Classification System (Akbulut, 1999; Kalkan, 2003; Kalkan and Bayraktutan, 2008, Rashed et al., 2017). Extreme precautions were taken during soil sampling to keep the collected soil samples in their natural moisture content and field density conditions. The particle size distribution curve of Barika clayey soil is shown in Figure 1. The tested sample can be classified, according to ASTM Standard (D422, 1990), as CL soil. The obtained properties of the untreated soil sample are summarized in Table 1. The selected lime for the study is hydrated lime, Ca (OH)2, white color in the form of fine powder.
Table 1: Geotechnical properties of the tested untreated Barika CL soil sample.