Mechanical aspects of construction of new TBM tunnel under existing structures

Abstract

It is inevitable for the construction of subways to pass under the existing structures in the city; this will cause settlement of the existing structures and affect their safety. The soil is a complex mixture, and hence it is difficult to determine the damage caused by construction using tunnel boring machine (TBM) method to the stress balance of the surrounding soil. Normally, settlement and uplift of the surface are caused during tunneling. Therefore, large-scale 3D simulations are needed to study the interaction between mechanically driven tunnel construction and the surrounding soil to estimate the expected settlement and related damage risks to the existing structures, especially in tunnel construction in urban areas. Qingdao Metro Line 1 in the Haixiao section (Xiaocunzhuang and Haiboqiao stations) was taken up as the research object to study the trend and degree of the effect of TBM tunnel construction using the numerical simulation software Midas GTS NX. The numerical simulation results and measured data were used for the reliability analysis to study the influence of different digging speeds and pressures in TBM construction on ground subsidence, and the effect of vibrations generated at the tunnel face by the TBM cutter head on the ground structure. It is shown that when other factors remain unchanged, the faster the driving speed, the smaller the ground settlement; the higher the surrounding rock pressure, the smaller the ground settlement. The vibration of the ground structure caused by the TBM cutter head complies with the relevant specifications. During construction, the driving parameters should be selected suitably depending on the available budget.

Composite evaluation method for route selection of linear underground space engineering based on numerical simulation and analytical hierarchy process

“…Relying on the Ma Wan cross-sea passage project, Chen Xiaoping et al constructed a rapid evaluation model for cross-sea tunnel route selection using AHP [7]. Additionally, some studies have used traditional numerical calculation methods to establish small-scale engineering models and simulate the excavation process of linear underground space projects to analyze the safety of the surrounding structures during excavation [8][9][10]. Xu et al used FLAC3D to establish a model of Beijing Subway Line 6 passing beneath Chaoyangmen Station and studied the deformation patterns of the existing station [11].…”