## 1 Introduction
[7] simulated a low strength (0.08-0.56 MPA) solid-fluid coupling similar materials, using fine sand, calcium carbonate, gypsum, paraffin, and Vaseline to study the fracture development of coal and rock mass under mining conditions and the distribution characteristics of water inrush and sand burst channel. [PERSON] [8] used sand and talcum powder as the aggregates and paraffin as the adhesive and mixed them with appropriate amounts of the regulator to form solid-fluid coupling similar materials. The paraffin-wax-like materials can solve the problem of solid materials disintegrating in the presence of water. Using stone, quartz sand, and bentonite as the aggregate, and silicon oil and Vaseline as the binders, [PERSON] et al. [3] prepared similar materials with low strength and high plasticity for a water-resisting layer, but the strength was too low and had a general level of plasticity. As it only simulated a weak water barrier, it is difficult to apply these results to harder aquitard layers. Physical similarity model experiments are important methods for studying specific large-scale engineering laws [9], and many scholars have achieved considerable success in this field of engineering related to seepage and water inrush during the mining process. However, there are still some problems in the fluid-solid coupling similarity model testing of seepage water gushing from mine roof aquifers. First, there are significant differences in the physical strength parameters of similar materials in aquifuge (aquitard) strata under different geometric similarity ratios when applying the fluid-solid coupling similarity simulation theory of underground mining. Another problem is that the physical model testing of the fluid-structure interaction has high requirements in terms of similar materials. To satisfy the deformation conditions of similar materials in the aquiclude (aquitard), similar conditions of water-physical parameters, such as low permeability, must be met at the same time [10,11]. Furthermore, the physical strength and hydro-chemical stability of similar materials cannot be guaranteed in the development of fluid-solid coupling similar materials, which is mainly manifested in the sudden change in the physical strength and hydro-chemical parameters of seepage water under seepage erosion and hydro-chemical action. Among similar materials, there are often situations where the selected raw materials undergo sustained and uncontrollable hydration reactions with the seepage water, resulting in more uncertainty in the physical model test results. Therefore, it is necessary to conduct further research on similar materials using convection solid coupling. In this paper, based on the existing research on the fluid-solid coupling of similar materials, river sand was selected as the skeleton of the material, gypsum and calcium carbonate powder as the auxiliary cementing agents, and paraffin wax and petroleum jelly as the waterproof cementing agents of the experimental raw materials. We conduct a comprehensive analysis of physical and mechanical strength and hydraulic parameters to simulate the similar materials of aquifuge (aquitard) strata in the process of fluid-solid coupling physical similarity model testing of \"water inrush in goat exists in the mine\". We review the similarity theory of the \"solid-liquid\" coupling and analyze the mutual regulation mechanism between paraffin wax and petroleum jelly in the physical mechanical strength, plasticity, and waterproofing of the samples. We also study the influence mechanism of physical and mechanical strength changes and the similar change in the hydrologic parameters of the similar material of the aquifuge (aquitard) layers. This study is of great value to the study of water inrush from mined-out areas and to the enrichment and development of fluid-solid coupling physical similarity and model test technology.