Experimental study on similar materials for tunnel lining concrete in geomechanical model tests

In geomechanical model tests, a reasonable proportioning of similar materials is one of the keys to ensuring that the physical and mechanical properties of the model match those of the prototype. Using gypsum, white cement, barite powder, quartz sand, and water as raw materials, a similar material of tunnel lining concrete was developed by orthogonal design. The density, compressive strength, elastic modulus, and tensile strength of the similar material were measured, which were evaluated using range analysis. Meanwhile, the mechanical parameter relationship was studied between the similar material specimens with different sizes. The results show that the similar material has a large range of physical and mechanical parameters, and can be used in the model test with a large unit weight; its ratio of compressive strength to tensile strength is 8.31–16.12, which conforms to the mechanical properties of concrete. The aggregates/cementing materials ratio has the largest impact on the material density, while the water/cementing materials ratio has the greatest influence on the strength and elastic modulus of the material. There is a good fitting relationship between the mechanical parameters of cylinder specimens and the mechanical parameters of cube and prism specimens, so cylinder specimens can be prepared for mix proportioning tests during trial preparation of the similar material. The physical and mechanical performance of grade-C25 concrete and grade-C40 concrete can be well simulated by the developed similar material. The research can provide a reference for the selection of similar materials for lining concrete in similar model tests.