Research progress on physical reconstruction of coal-rock mass and roadway model test based on sand-powder 3D printing

The surrounding rock of roadways often contains complex joint fractures, holes of different sizes, and other internal structural characteristics, which seriously affect their stability. Indoor physical model tests are one of the main ways to study the stability of engineering rock masses. However, traditional methods struggle to produce physical models with exactly the same structures and properties, and the mechanical properties and internal structures of physical models differ considerably from those of in-situ rock masses, which greatly limits the scientific nature of physical model tests in reflecting the actual engineering roadway. In recent years, the rapid development of 3D printing technology has effectively made up for the shortcomings of traditional methods. At the level of material research and development, sand-powder 3D printing coal-rock-like materials with high similarity to natural coal-rock in mechanical behavior are successfully prepared by systematically regulating printing matrix, particle gradation, binder saturation, and glass fiber content. This progress lays a material foundation for the production of physical models. At the level of mechanism research, based on mechanical tests on anchorage bodies using such coal-rock materials, the anchorage mechanisms of supporting elements such as bolts have been systematically revealed. These tests verify the feasibility of using these materials to simulate the anchorage in natural rock masses and provide a theoretical basis for the design of supporting structure. Finally, at the level of physical model tests, researches have employed the sand-powder 3D printing technology with the layered printing process to construct physical models of anchored roadways under the conditions of both intact surrounding rock and fractured surrounding rock. The influence of cracks on the deformation and failure law of roadway is quantitatively analyzed with the aid of the biaxial loading system and the digital speckle technique (DIC). The failure modes revealed by the tests are highly consistent with the field observation results. Collectively, these studies confirm that the sand-powder 3D printing technology can achieve high-precision reconstruction with respect to material properties, internal structure, and mechanical response, effectively overcoming the shortcomings of traditional model tests and showing good application prospects and scientificity in physical simulation research of rock mass engineering.