Multistage-based evaluation of tunnelling effects on the skin friction of adjacent building piles in layered media

Abstract

Pile skin friction performance has been recognized as a significant role in the stability of structures adjacent to underground tunnel constructions. Many previous studies paid attention to the ultimate bearing capacity of the pile when undergoing tunnel excavations, but the skin friction response to multistage tunnelling process is still far from clear. This paper conducted multistage-based modelling about the effect of tunnelling process on the pile-soil interaction in layered soil media, which aims at examining the skin friction performance of the single pile and pile group subject to both vertical building loads and adjacent shield tunnelling. Based on the multistage modelling of the tunnel excavation process, the distribution features and mobilization patterns of the skin friction on single piles were obtained as tunnel excavation continuously proceeded towards the single pile and away from it. In addition, the skin friction behaviours of the double piles and pile group adjacent to shield tunnelling in multi-stages were compared with that of the single pile under the same conditions. The research results show that adjacent tunnelling could cause stress release and additional settlement of the surrounding soils and thus change the distribution features of skin friction of building piles. For double piles, the isolation and dragging effects from the interaction between the front pile and the rear pile are presented and examined. The skin friction distribution on double piles during tunnelling process is primarily dependent on the distance of the pile from the tunnel centreline. For pile groups, the negative skin frictions are easy to appear on the side piles and the centre pile subjected to both vertical loading and adjacent tunnelling.