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Abstract Against the background of the Liangshui tunnel of Lanzhou—Chongqing line and based on 3D large-scale geomechanical model test of excavation and support on large cross-section tunnel，the process of surrounding rock load releasing during tunnel excavation is studied. New similar material is developed according to the field geological condition，which is proved by the laboratory tests to be similar to original rock materials on mechanical properties and meets the test requirement. Construction methods of excavation and support on different sections are various and the load releasing processes of surrounding rock on full-face excavation and bench-cut excavation are compared firstly. Through analyzing the test data，the features and differences of load releasing processes with different excavation methods are revealed. There are great differences in load releasing processes at different locations of the same section using the same excavation method. Meanwhile，the load releasing process at the same locations of the same section are various when different excavation methods are used. Secondly，the phenomenon of first load concentration occurs in front of tunnel face affecting by the excavation. The degree of first load concentration is related with the excavation method and section form. High degree of load concentration in front of tunnel face would aggravate the crowding-out effect，which is unfavorable to surrounding rock stability. Lastly，by comparing the load releasing processes of support excavation and non-support excavation，it is known that support can response the first load concentration effectively，reduce the load releasing amount，and optimize the load releasing process of surrounding rock in construction.
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Received: 15 September 2011
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2012, Vol. 31 
