Abstract
Techniques including pre-grouting, long pipe roof, and parameter optimization were employed to ensure the safety of loess metro tunnelling under an existing glass building. Their effects were proved through monitoring the settlement of building and surface during tunnelling. Besides, division of settlement monitoring according to processes, a new method, was conducted to control settlement in time. The highest surface settlement after construction was 16 mm only, meeting the requirement. The result indicates that it is practicable to control the tunnelling settlement strictly in extremely difficult geological areas. The settlement regularities were also studied through numerical simulation; their deformation is larger compared with in situ results while their change trends coincide during most processes. Soil excavations cause settlement primarily, accounting for more than 60%. It is suggested that dual slurry pre-grouting and process-based measurement should be employed before each excavation in water-rich loess areas.
Highlights
With the boom of urbanization and heavier traffic on the roads, the metro plays an increasingly important role
Metro tunnels are primarily constructed by shield method
Limited to difficult geological environment like ground fissure area, it has to be substituted with shallow tunnelling method (STM) sometimes because the parameters of shield machine cannot change rapidly with the various soil formations. en, some adverse consequences follow due to the disadvantage of STM method per se
Summary
With the boom of urbanization and heavier traffic on the roads, the metro plays an increasingly important role. Limited to difficult geological environment like ground fissure area, it has to be substituted with shallow tunnelling method (STM) sometimes because the parameters of shield machine cannot change rapidly with the various soil formations. Metro tunnels were constructed under an existing building with glass exterior walls that are extremely sensitive to settlement in loess strata. E challenge of this project lies in the fact that (i) the surface building is ageing, and its external wall materials are unable to absorb large settlement; (ii) it is difficult to control the deformation in shallow tunnelling, which is easy to cause large settlement or even collapse; (iii) the project is adjacent to a ground fissure, and the soil is soft, aqueous, and unstable. E project was constructed with the following steps: (i) tunnelling the 9.68 m right line through the south shield hoisting hole and the north temporary dumping soil passageway; (ii) setting up the large pipe roof above the vault of 39.33 m tunnel on the left line directly; (iii) undermining left tunnel from south to north via alleyways of right line and Tonghuamen Station
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
