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Abstract In order to study the process of construction mechanics under different excavation methods，a large-scale model test system is developed. Its maximum external dimensions is 5.2 m wide，4.5 m high，and 2.7 m thick. It has the features of stressing definite，reasonable structure. It can be disassembled and combined at will. Automatic hydraulic control system has the features of high pressure，long pressure holding time，steady loading and loading in gradient，etc. Various 3D and 2D geomechanical model tests of underground engineering can be satisfied. On the basis of the existing geomechanics similar material，a material ratio was attained for soft rock by a large number of different material ratios with their mechanical parameters being tested. Large scale 3D geomechanical model test about construction process of railway tunnel was developed. The changing mechanical process was simulated truthfully. Test results show that the test system is stable and reliable，and can be widely used for geomechanical model test in other underground engineering；research methods，techniques and the results make certain guiding significance to the practical engineering.
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Received: 28 January 2011
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2011, Vol. 30 
