The term SENS stands for Shield ECL NATM System. Excavation is conducted by maintaining the stability of the face with the shield tunneling method, while aiming for early closure with primary support that applies the extruded concrete lining (ECL) method. The tunnel is completed by casting concrete for the secondary lining after the displacement convergence of the ground, as in the case of spraying concrete with NATM. This method is applied for constructing 11-meter-diameter tunnels for the Shinkansen (bullet train) and other railway tunnels. Special equipment machines that permit switching between the shield tunneling method and SENS method have also been put into practical use.
The SENS method is establishing its position as a method with cost benefits for works in the boundary between the mountain NATM and the shield tunneling method in terms of ground property. Above all, it is expected to make a significant contribution in the fields of large-diameter tunnels, non-circular tunnels, and long tunnels.