Vertical Earth Pressure for a High-Filled Cut-and-Cover Tunnel: Site Measurements and DEM Simulations

Abstract

Determining vertical earth pressure (VEP) is crucial in designing high-filled cut-and-cover tunnel (CCT) structures. This parameter directly influences the safety and economy of the structure. However, the current pressure formulations do not adequately account for the numerous influencing factors that affect VEP for CCTs, including filling height, slope rate, and tunnel span. In this study, the effects of these factors on VEP were investigated through a combination of field tests and discrete element method (DEM) simulations. An empirical formula for VEP suitable for high-filled CCTs was obtained through mathematical regression. The findings indicated that the soil arching effect is present in high-filled CCTs once the backfill reaches a certain height. The final VEP on the vault was only 0.74 times the total overburden weight. The pressure reduction coefficient decreased with increasing filling height and slope rate but increased with rising tunnel span. The proposed empirical formula for VEP took into account the discount of earth pressure under various factors. It is consistent with the field test results, providing a better reflection of the actual VEP for high-filled CCTs.