MEASURED DEFORMATIONS AND EXPECTED ANALYSIS CAUSED TO THE EXISTING TUNNEL DURING NEARBY CONSTRUCTION OF UPPER AND LOWER PARALLEL SHIELD TUNNELS

Abstract

 Twin large shield tunnels for highway services were excavated above and below an existed shield tunnel. The deformations of the existing tunnel were measured during nearby shield tunneling. The vertical and horizontal inner deformations of the existing tunnel were measured by specific fiber optics being called BOTDR. The deformations of the cross-section of the existing tunnel were detected with an accuracy of 0.05 mm. This paper is described remarkable knowledge of the vertical and horizontal deformations of the cross-section of the existing tunnel being influenced by upper and lower parallel shield tunneling. The authors also proposed the simple 2D FEM with the inclusion of the self-weight of the shield machine in the simultaneous excavation of vertical parallel shield tunnels. The construction data being corresponded to the shield tunneling are applied to analyze the changes of the deformations of the existing tunnel and nearby ground stresses. The results of the calculation showed good agreement with the deformations of the cross-section of the existing tunnel. As the result, we could propose a predictive calculation method for vertically parallel shield tunneling.