Ultra-low permeability rock-analogue material for gas–solid coupling model tests

In fluid–solid coupling model tests, most existing rock-analogue materials have high permeability, making them unsuitable for gas–solid coupling model tests. Here, a new type of rock-analogue material was developed, which catered to gas–solid coupling model tests that used iron powder, barite powder and quartz sand as aggregates, a special cement as a binder and a cement sealant as a regulator. The physical and mechanical parameters of the material and its influence patterns were determined by laboratory tests. The results showed that the material had a uniaxial compressive strength of 4·16–8·8 MPa and a permeability of 1–460 × 10⁻³ mD, which is stable at a gas pressure of 1·5 MPa. The density, uniaxial compressive strength, modulus of elasticity and permeability of the material could be precisely adjusted by the moulding pressure, binder content and regulator content. The material can be used to simulate rock with high strength and ultra-low permeability in gas–solid coupling model tests. A model test of coal and gas outburst triggered by roadway excavation was successfully performed using this material to simulate the roof rock and floor rock of a coal seam with low permeability, which demonstrates the feasibility and applicability of the material.