Effects of particle size on compressive deformation characteristics of broken rock mass in gangue rib of automatically formed gob-side entry retaining

In automatically formed gob-side entry retaining techniques, one side of the retaining roadway consists of the gangue rib structure. The stability of the gangue rib and the movement of the overlying strata are significantly influenced by the compressive deformation characteristics of crushed stones. In this research, a large gangue rib similar compression device was designed to perform compression tests on gravel of different particle sizes. Additionally, a novel three-dimensional gravel compression simulation method was introduced, which involved the construction of irregular crushable clusters to simulate the compression and re-crushing process of gravel. The findings indicate a positive correlation between particle size and compression ratio under increasing stress. The gangue exhibits a prominent skeletal load-bearing effect, characterized by repeated processes of load-bearing, crushing, filling, and load-bearing. During compression, the porosity of the gravel decreases exponentially, and larger particle sizes result in higher degrees of fragmentation, showing a tendency of layered compaction.