Abstract:

In order to guarantee the smooth implementation of first domestic shield tunnel crossing underneath turnout groups of railway turnout area in waterrich sandy cobble stratum, the methods of engineering analogy, numerical calculation and field monitoring are adopted to propose a deformation control standard of less than 1 mm/d for track bed and track based on train running speed and track bed form; and a series of active control countermeasures, i.e. large and superlong pipe roof support, existing pedestrian passageway reinforcement and tracing grouting, and shield pressure maintaining and sectioned boring during railway skylight period, are put forward under the condition that vertical and horizontal lifting beams cannot be constructed. The practice results show that: (1) The jacking technology, bit stiffness and orientation control technology are the keys to high precision and superlong pipe roof construction in dense sandy cobble stratum. (2) The reinforcement for the existing pedestrian passage beneath railway can play a role as longitudinal lifting beam with large stiffness; and the Soletanche tracing grouting conducted in both side of pedestrian passage can effectively compensate for ground loss and disturbance displacement induced by shield tunneling. (3) The adverse influence of shield sectioned boring in skylight period can be controlled when cabin pressure and stability of tunnel face can be guaranteed.

Key words: shield tunnel, waterrich sandy cobble stratum, railway turnout area, turnout groups, high precision and superlong pipe roof, lifting beam with large stiffness, shield sectioned boring in skylight period