Effect of multi‑faced twin tunneling in different depths on a single pile

摘要

In this paper, 3D modeling was performed to understand the effects of excavation of twin tunnel on a single pile in weathered residual soil. The effect of various tunnel depths on pile was evaluated in two cases of Z/L-p = 0.8 (tunnels near the pile shaft) and Z/L-p = 1.2 (tunnels below the pile tip). The effect of different patterns of the New Austrian tunneling method including top heading, central diaphragm wall, and sidewall drift on behavior of a single pile was also studied. The results of study showed that TH pattern reduced pile settlement by 36.5 and 15.9% at Z/L-p = 0.8 and Z/L-p = 1.2, respectively, compared to other patterns considered in twin tunneling. In the case of Z/L-p = 1.2, TH pattern caused the minimum magnitude of tensile force in the pile compared to other tunneling patterns. Besides, results obtained from analyses indicated that zone of influence of tunneling was independent of tunneling patterns, and it can be identified as +/- 2D (D is the tunnel diameter) based on pile head settlement in longitudinal direction.