Earth Pressure Balancing (EPB) machines are commonly used to excavate tunnels in soft soils ranging from coarse-grained soils, sands to hard clays. The design of these machines is such that the excavated soil inside the pressure chamber is used to apply holding pressure to the face of the auger during excavation. The ideal soil for an EPB machine is soil that, after being excavated and entering the pressure chamber, becomes a plastic and doughy material capable of applying pressure to the auger. It is obvious that real soil in nature rarely has such properties. Thus, soil treatment technology has emerged over the past decade to overcome these problems. The process of adding foam and polymer to the soil is called treatment operation. In tunneling with EPB machine, the behavior of excavated soil from the time it is mixed with foam in front of the machine cutterhead until it exits the spiral conveyor depends on the workability characteristics of the treated soil. Factors that affect soil workability include strength index, moisture content, fine particle content, and foam injection ratio (FIR). The main objective of this paper is to investigate the effect of the above parameters experimentally on the workability of soil treated with foam and compare it with the actual data of Tabriz Urban Railway Line 2 in order to evaluate the mechanical parameters of the soil.