What key design parameters determine the optimal shape and material of a tunnel lining segment?

Several key design parameters determine the optimal shape and material of a tunnel lining segment. The external loads, including earth pressure, water pressure, and surcharge loads from surface structures, are primary. The shape and material must be able to withstand these forces without failure. The tunnel diameter and geometry dictate the segment size and curvature. Larger tunnels require larger segments, and the segment geometry must match the tunnel's shape. G....