Since the important structures are often located across or near by tunnels under construction in urban areas, the ground surface settlement is quite important and unavoidable. Especially when a shallow tunnel is excavated in unconsolidated ground, the ground displacement shows often the characteristic non-linear movement influenced by the soil mechanics. The authors conducted two kinds of excavation methods in the diluvial sand layer and vertical anchor volts works to support the excavation in the bank. In the paper the authors analyze the mechanics of ground surface settlement by applying the back-analysis method, and conduct the technical evaluation for effectiveness of each preventive method and works.