Evaluation of deformations and stability of a NATM tunnel: case study Djebel El-Ouahch Tunnel, Algeria

Excavating underground structures, like tunnels or galleries, disrupts the soil's stress and deformation state, potentially compromising excavation stability and inducing significant ground damage. Ground movements are common challenges during such constructions, often attributed to adverse geological, geotechnical, or hydrological conditions, including groundwater-induced swelling and seismic loads. This article aims to model a pathological case of the T1 tunnel of Djebel El Ouahch (East-West highway). It studies the pathological conditions by examining the stress and strain states both in the surrounding soil and in the tunnel wall. To do this, a numerical analysis was carried out using the FLAC2D calculation code, which uses the finite differences method (DEM) to study the stability of a section of the T1 tunnel, calculate the stress state, and evaluate soil displacements and their impact on the structure.