Study on ground deformation due to small-clearance twin shield tunneling with different construction sequences

Different construction sequences can lead to stress redistribution in surrounding strata, triggering ground deformation problems. However, the existing studies mainly focus on the ground deformation caused by a single asynchronous or synchronous twin tunnel construction, and less consideration is given to the effects of different construction sequences. This paper relies on a small-clearance twin shield tunnel project in Xiong'an New Area, establishes a numerical model by using ABAQUS finite element software, verifies the reasonableness of the model through on-site measurements and Peck calculations, and investigates the effect of construction sequence on the deformation of the ground layer in the construction of twin shield tunnels. The results show that the construction sequence has significant influence on both vertical and horizontal displacements of the strata. In terms of vertical displacement, compared with asynchronous tunneling, the maximum vertical displacement (along the cross-section) and the width coefficient of the sinkhole of synchronous tunneling increased by 34%~35% and 20%~25%, respectively; the vertical displacement (along the longitudinal cross-section) increased by 20%~33% and 34%~58% at the ground surface and at the 0.5D below the tunnel, respectively. For the horizontal displacement of the ground, compared with asynchronous boring, the maximum horizontal displacement of synchronous boring on the left and right sides of the two tunnels increases to 46%~47%, and the maximum horizontal displacement in the middle of the two tunnels almost decreases to zero.