Abstract: The classical Peck’s formula fails to account for the impact of tunnel’s section shape and buried depth on surface settlement in shallow-buried tunnels with large section. To address this limitation, we introduced a modified Peck’s formula by incorporating correction coefficients for sectional shape and buried depth, and verified the validity of the modified formula using measured surface settlement data of the Baitashan Tunnel. The average relative error between predicted and measured values for two monitoring sections is 8.3%, with a maximum relative error of 18.4%. Additionally, we employed the modified Peck’s formula to predict surface settlement resulting from tunnel excavation under various sectional shapes and buried depths. The results demonstrate a positive correlation between the maximum surface settlement and the sectional shape correction coefficient, with the following order of maximum surface settlement predicted: rectangle-1(Ⅰ) > horseshoe-1(Ⅱ) > circle (V) > rectangle-2(Ⅲ) > horseshoe-2(Ⅳ). As the burial depth of the large-section shallow-buried tunnel increases, the maximum surface settlement decreases, and the width of surface settlement groove correspondingly widens. The surface settlement curve transitions from being narrow and deep to wide and shallow, while the area of core settlement gradually diminishes. The outcomes presented in this study provide theoretical support and serve as a technical reference for similar projects.

Key words: shallow-buried tunnel with large section, surface settlement prediction, Peck’s correction formula, sectional shape