Abstract: According to similarity principle of geomechanical model test, a new type cementitious geotechnical similar material called iron crystal sand is developed through a lot of material mechanics test. This similar material is evenly mixed with iron ore powder, blanc fix, quartz sand, gypsum powder，rosin and alcohol in certain proportion and pressed together. Iron ore powder, blanc fix and quartz sand are main materials, the solution of rosin alcohol is cementing agent, gypsum powder is regulator. Specimen mechanical tests show that the new-type similar material has many remarkable advantages as follows: high volume-weight, wide variable mechanical parameters, stable performance, low price, easy dryness, easy processing and without any toxicity and side effects. It can be used to simulate most of rockmass material from soft to hard ones. The new typed material has been used in 3D geomecanicl model test of bifurcation tunnel of Sanghai-Chendu-Xichang expressway and mechanical deformation properties of rockmass surrounding bifurcation tunnel have been effectively revealed under excavation state.

Key words: similarity principle, new type geotechnical similar material, mechanical test of material, 3D test model of large-scale bifurcation tunnel