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Abstract Separated two-track tunnels of Beijing Metro Line No.4 Xuanwumen station vertically cross beneath Line No.2 Xuanwumen station. Analyzing the measured displacement of the existing station structure both from the global deformation and the single structural block displacement，we obtain the deformation law of the overlying existing structure during excavation by steps. Research shows that：(1) The existing underground structure′s integral settlement complies with Peck formula，but the displacement of single block between two movement joints is rotation mainly and presents rigid body rotation. (2) The ground loss ratio fitted by Peck formula is 0.118%–0.187%. It is unrelated to the existence of the underground structure and the size of excavation section，but it is associated with the new tunnels′ supporting time and supporting stiffness. (3) The settlement trough width coefficient fitted by Peck formula is 2.44–3.87，which is the 1.05–1.62 times than the coefficient of natural stratum. It is unrelated to supporting stiffness，but it is associated with the reinforcement method，the existence of underground structure and the size of excavation section. The research result can provide reference for the similar engineering.
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Received: 20 February 2013
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2014, Vol. 33 
