Jung-Feng Chang, I-Chou Hu, Ting-Chiun Su, and Hsiao-Chou Chao
Moh and Associates, Inc., Taipei, Taiwan
"ABSTRACT: With limited space in urban area, one viaduct line of Taipei Rapid Transit is designed to partially overlap the alignment of another underground line that is currently in operation. The pile foundation of the viaduct line in the overlapped region is thus built in between the up- and down-track shield tunnels of the underground line. To investigate the soil-pile-tunnel interaction behind this close construction, the 3D model of Midas/GTS is adopted to simulate a series of construction steps for cases with various covering and spacing of tunnels. Through 3D modeling, it is found that effects of pile loading on tunnel deformation are greater than those of pile construction using casing methods and under proper procedure. The longitudinal range of influence on tunnels is approximately restricted to 2 times of cap length from the centreline of the cap. In addition, the effects decrease with increasing spacing and covering of tunnels."