Model Test on the Multi-Effects of Tunneling and Excavation upon an Existing Pile in Clay.

Existing studies often analyze tunnels and excavations as isolated projects, but in practice they are often constructed sequentially or simultaneously. This paper investigates their combined effects on adjacent pile foundations in clay using constant-gravity model tests and 3D numerical methods, considering time-dependent clay behavior and small-strain stiffness. Two combined construction sequences of tunnelling and excavation adjacent to an existing pile were investigated: (i) tunnel excavation followed by basement excavation (i.e., test TEP); (ii) basement excavation followed by tunnel excavation (i.e., test ETP). Results show that construction sequence has little effect on surface settlement but significantly influences pile response. Pile top settlement increases considerably when tunnelling occurs near piles. The TEP sequence reduces cumulative pile top settlement by 0.38% of the pile diameter and reduces the maximum cumulative bending moment by approximately 31% compared with the ETP sequence. Additionally, tunnel and excavation construction generate negative excess pore water pressure in the surrounding soil, which dissipates over time. The pressure increases with proximity to the tunnel face or excavation base.