Construction techniques and mechanical behavior of newly-built large-span tunnel ultra-short distance up-crossing the existing shield tunnel with oblique angle

In recent years, with the rapid increase of urban subway lines, crossing engineering has become another complex problem of modern tunnel construction techniques, and especially ultra-short distance up-crossing engineering has attracted wide attention. Based on the project of the new large-span tunnel ultra-short distance up-crossing the existing shield tunnel with oblique angle, deformation and mechanical space-time effect of existing shield tunnel was carried out in the present work, and the micro deformation control techniques of the " bench pile + large-diameter pipe roof + cable" combined bearing-reinforcement system was proposed. Firstly, the key construction techniques in this project were introduced, and the vertical deformation law of the ground surface, the arch foot and the ballast bed of the existing tunnel was researched. Then, by comparing with the field measured results, the accuracy of the numerical model was verified, and the overall deformation, internal forces and torsion behavior of the existing tunnels induced by the construction of new tunnel were obtained. Finally, the effect of technical measures to control the deformation of the existing shield tunnel was analyzed in detail. The results showed that the micro deformation control techniques of " bench pile + large-diameter pipe roof + cable " proposed in this paper can effectively control the deformation of existing shield tunnel, which provides a new deformation control system for similar projects.