Abstract: In physical similarity simulation experiments, the similarity between the physico-mechanical properties of similar materials and the physical properties of simulated prototypes is the key to the success of physical similar simulations. In order to determine the physico-mechanical properties of physical similar materials, three factors and four levels of orthogonal experiments are used; and the influence of three factors, such as sand binder ratio, density and residual moisture content, on the uniaxial compressive strength, elastic modulus and Poisson's ratio of similar materials are studied by using the similar materials composed of sand and gypsum. The results show that the factors affecting the degree of uniaxial compressive strength from big to small in turn for the sand binder ratio, density, residual moisture content; and the uniaxial compressive strength increases with the increase of density but decreases with the sand ratio and residual water content increases. The factors affecting the degree of elastic modulus from big to small in turn for the sand binder ratio, density, residual moisture content; and the elastic modulus increases with the increase of the density, decreases with the increase of the sand binder ratio. The factors affecting the Poisson's ratio from big to small in turn for the residual water content, density, sand binder ratio; and the Poisson's ratio increases with the increase of density and residual water content, but not to the sand binder ratio. The density, sand binder ratio and residual moisture content have a certain interaction with the uniaxial compressive strength; but they do not exist on the elastic modulus; and the density, sand binder ratio have a certain interaction with the Poisson's ratio of similar materials. The regression equation of the ratio of sand to shell, density and residual water content on uniaxial compressive strength, elastic modulus and Poisson's ratio is obtained; and it is of great significance for the design of similar materials.

Key words: similar material, physico-mechanical properties, orthogonal experiment, sensitivity, interaction