Design and construction of a seismic physical model of room-pillar goafs in shallow coal seams

In view of the problem of low detection accuracy of room-pillar goafs in shallow coal seams in northern Shaanxi, the seismic physical model is designed for physical simulation according to the principle of similarity ratio of geometry size and wave impedance. Through a large number of ratio tests of similar materials, the ratio of epoxy resin and silicone rubber is determined as 1 : 1.2 for similar materials of low velocity loess layer, 1 : 0.2 : 0.6 for epoxy resin, silicone rubber and talc for mudstone, 1 : 0.4 for epoxy resin and silicone rubber for coal seams, 1 : 0.8 for epoxy resin and talc for argillaceous sandstone, and 1 : 1.2 for epoxy resin and talc for sandstone. The numerical control engraving machine is used to carve the coal seam goaf and roadway to ensure high precision. By using the pouring method combined with the bonding method, the sandwich layer of goafs and coal seams is made to solve the problem of air model production in the goaf roadway, and the seismic physical model of the room-pillar goaf roadway is completed. The single-layer shape measurement accuracy of the physical model measures 0.2 mm, the speed relative error less than 5%, and the density absolute error ±0.3 g/cm³, which meets the design requirements of the model.