The pressure applied to the tunnel face during excavation plays a significant role in ensuring the tunnel face stability. The tunnel face collapses at lower pressure and blasts out at higher pressure. In the present study, tunnel face stability analysis has been carried out under dry and seepage conditions for both \(\varphi\) and \(c-\varphi\) soil. The effects of tunnel geometry, including the tunnel diameter (D = 5.0, 7.5, 10.0) and cover-to-diameter ratio (C/D = 0.5, 1.0, 2.0, 4.0)] as well as the shear strength parameters of soil [Cohesion (c) and angle of internal friction (φ)] have been studied. A linearly proportional relationship has been observed between the face pressure and the tunnel diameter (D). The face pressure has been found to increase linearly with the increase in the value of the (H/D) ratio, irrespective of the soil type. Based on the observation of the parametric study, mathematical models have been developed to compute the stability numbers in dry ( \({N}_{\gamma }\) and \({N}_{c}\) ) and seepage ( \({N}_{\gamma }{\prime}\) and \({N}_{c}^{\prime}\) ) conditions as a function of the angle of internal friction (φ) of soil. Based on soil types and drainage conditions, appropriate solutions have been proposed to find the face pressure. The face pressure predicted by the present model has also been validated with the experimental studies of previous researchers. Hence, the developed numerical model may find potential application for the assessment of face pressure in \(\varphi\) and \(c-\varphi\) soil under both dry and seepage conditions.
