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Abstract During the actual construction process of subway tunnel，the surrounding rock is in a complex process of loading and unloading. Meanwhile，the excavation and support are completed in multiple steps. During this process，the previous excavation step will influence the subsequent excavation. Based on the characteristics of underground engineering，that is，loads are applied first，then excavation is conducted，and supports are provided at last，the actual construction process of subway tunnel under excavation unloading effect was described and simulated. The excavation unloading effect during the process of subway tunnel construction was analyzed in detail；and the 4-stage simulation method was put forward，which can simulate the excavation unloading effect during the construction process of subway tunnel. Taking the tunnel in Xisanqi—Qinghe section of Beijing metro line No.8 as engineering background，the actual process of shield construction of subway tunnel and the excavation unloading effect were simulated. The effects of excavation face supporting pressure，supporting time and filled grouting on excavation and support of metro tunnel were studied，with and without consideration of the excavation unloading effect. The surrounding rock-support working mechanism of metro shield tunnel was obtained based on the excavation unloading effect.
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Received: 18 November 2011
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2013, Vol. 32 
