A shallow foundation measuring 1 m × 2 m in plan is to be constructed over a normally consolidated sand layer. Given: D_f = 1 m, N₆₀ increases with depth, N₆₀ (in the depth of stress influence) = 12, and q_net = 153 kN/m². Estimate the elastic settlement using Burland and Burbidge’s method (Section 9.6).