**4. Clayey sand subgrade**

As mentioned in the last paragraph, the percentage of fine particles smaller than 0.06 indicates RRP235special dosage. The soil was brought from Urmia railway station. Typically the region soil has enough clay.

The primitive soil tests such as particle size distribution were done, and the type of soil was specified. Results revealed 40–50% of soil was smaller than 0.06 mm (**Figure 3**).
