Experimental Study of Similar Simulated Material Proportioning for Small Scale Models

The development of materials formulated for similar simulation testing of small-scale models is the foundation of this work in order to carry out the physical model test investigation of the instability mechanism of the retrieved roadway beneath the legacy coal column on the close coal seam. In this paper, river sand is chosen as the aggregate and gypsum + cement as the cementitious material, and an orthogonal test with three factors and five levels is designed, as well as sensitivity and error source analyses of the test results. The results showed that river sand content and water content had significant inhibitory effects on the longitudinal wave velocity, compressive strength, and tensile strength of similar materials, and had some but not significant effects on density, elastic modulus, and Poisson's ratio of similar materials. The gypsum-cement ratio had no significant effect on any of the six mechanical parameters of similar materials. For the sources of errors in each stage of the whole similar material fabrication process, corresponding methods and measures are proposed to reduce the errors. The experimental results are also fitted by multiple linear regression method, and the fitting results can better provide a reference for the formulation of similar simulation materials for small-scale models.