Prediction of Excavation Disturbance and Required Support Force for Tunnel beneath Existing Structural Foundations

Abstract

[Objective] It is inevitable that construction of new tunnels or other underground engineering projects will pass through some building structures, causing disturbances to the existing structural foundations. Therefore, it is essential to study the required support force for tunnel excavation beneath existing structural foundations and its variation under different conditions. [Method] Considering two scenarios of tunnels directly beneath and laterally passing existing structural foundations, mechanical analysis models for tunneling beneath existing structural foundations are constructed. Using the upper-bound theorem, theoretical formulas for calculating the required support force and critical foundation base pressure are derived. The impact of factors such as crossing position, soil mechanics parameters, and foundation pressure on the required support force for new tunnel excavation is analyzed. [Result & Conclusion] The relative position between the new tunnel and the existing structural foundation significantly influences the safety of the tunnel and the required support force. Compared to lateral crossing scenarios, tunnels directly under-passing existing structural foundations pose a greater risk to tunnel structural integrity. The required support force of the tunnel is negatively correlated with the tunnel-foundation burial depth difference, soil mass cohesion and internal friction angle, and positively correlated with soil mass weight and critical foundation base pressure.

Keywords

• tunnel
• existing structural foundation
• support force