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Abstract In the field of multi-arch tunnel，determining loose zone of surrounding rock has important theoretical value and practical significance for taking appropriate method for support in actual projects. By taking highway multi-arch tunnel with overburden depths of 100 m for example，a model test based on similar principle is implemented to study loose zone of the soft and fractured surrounding rock，and the characteristics of stress field in loose zone are analyzed through measuring pressure of different locations by pressure cells. FLAC software is applied to simulate model test. The range of loose zone is identified by stress analysis method and ultimate tensile strain method. Comparing with results of model test shows that tangential stress is greater than radius stress in loose zone，surrounding rock is more likely to form pressure arch under deep overburden condition. The range of loose zone decided by stress analysis method is closer to the results of model test，identifying loose zone is feasible for deep overburden tunnel by stress analysis method.
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Received: 12 January 2012
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2013, Vol. 32 
