<p>This study employs the adaptive finite element limit analysis(AFELA) method to simulate the failure modes of the soil behind retaining walls of foundation pits above tunnels undergoing excavation. The effects of factors such as vertical and horizontal relative distances of the tunnel, excavation insertion ratio, and soil strength on soil failure were analyzed. Based on finite element simulation results, a portion above the horizontal plane at the bottom of the retaining wall was used to construct a characteristic line field. Three types of boundary value problems were solved for different regions to assess the earth pressure distribution. The stress state at various points within the plastic zone was calculated to determine the earth pressure on the retaining walls of foundation pits above tunnels in their limit state. A comparison of results from the Stress Characteristic Method(SCM) and finite element simulations showed strong consistency, validating the efficiency and accuracy of the Stress Characteristic Method in calculating earth pressure on retaining walls above tunnels undergoing excavation.</p>