Tunnel excavation causes stress redistribution in the rocks surrounding the tunnel. This action causes a tendency for convergence in the tunnel wall. Depending on the characteristics of the ground, convergence may reduce the excavation cross-section or cause the crown and abutment of the tunnel to collapse. To prevent collapse, it is necessary to strengthen the rock mass and soil of the abutment. The umbrella arch is one of the pre-consolidation systems that is implemented in an arch shape at the top of the tunnel before excavation. A correct understanding of how the umbrella arch works requires complex calculations that are made possible by numerical modeling methods. This study examines how the umbrella method works and its effect on the Taghan-Hashtgerd road tunnel. Part of the cross-section of this tunnel has a high collapse potential due to its location in loose and shale materials. For this purpose, the tunnel with umbrella pre-retention has been numerically modeled using FLAC 3D software. In this study, in addition to investigating the necessity of using the umbrella arch, the effect of geometric and physical parameters such as the distance between the pipes and the diameter of the pipes on the stability of the tunnel has been investigated. The criteria for investigation are the vertical displacement at the tunnel crest, Sakurai relations, and the investigation of the stability of the pipes. The results show that increasing the diameter and reducing the distance have a positive effect on the stability of the tunnel. Also, the umbrella method has led to a reduction in the displacement of the tunnel crest by 36%.