Spatial size effect study of broken-expansion mass using rock-like materials under the 110/N00 mining method

The spatial size effect (SSE) of the broken-expansion mass is crucial in mining engineering, particularly with the promotion of the 110/N00 mining method. We analyzed the broken-expansion characteristics of bulking mass and introduced the space ratio and SSE coefficient to understand the SSE of broken-expansion mass. The results and analyses show a clear SSE in broken-expansion mass, and the suggested space ratio can be utilized to describe SSE. When the space ratio increases, the initial (KI) and residual (KR) broken-expansion factors increase, and the greater the space ratio, the more rapidly the increase. KI generally determines KR, but the compression inhibits SSE. The proposed SSE coefficient can express the SSE and the inhibition. Additionally, the SEE coefficient explains the SSE differentiation in the displacement characteristics. A larger space ratio leads to a greater volume reduction. Meanwhile, the bulking samples show a growing compressive capacity, and it can benefit from a smaller accumulation area. Compression failure in bulking mass is a dynamic process where structures change from loose to firm. The upper samples fail and fill voids, and the lower samples adjust positions to prevent failure. Finally, the discussion suggests the implications to the 110/N00 mining method.