Abstract: Along with the increasing of buried depth of underground engineering, the boundary condition of geomechanical model test has become one of the most important problems restricting the scientificity of simulation test in deep rock mass. The flexible uniform pressure loading technique has made it possible to equally distribute the boundary stress. However, the boundary condition can still not be met strictly. In this paper, the stress and displacement of surrounding rock mass of real excavation have been analyzed based on elastic-plastic theory. The main source of error in simulating deep rock store environment under the existing loading conditions and the reason why the deep environmental simulation can not be accepted have been revealed. Loading method by using a combination of springs as an equivalent action of peripheral rock mass has been presented to simulate boundary conditions. And the formula of equivalent springs stiffness of loading plate has been deduced by the equivalence of the displacement and stress, and both the advantages and disadvantages of this method have been discussed.

Key words: deep rock mass, model test, boundary condition, laboratory simulation