Exploring Pore Structure Features, Crack Propagation and Failure Behavior of Fiber Reinforced Foam Tail Fill by CT Imaging and 3D Reconstruction

Fiber-reinforced foam tail fill (FRFTF) has been widely investigated in the field of foamed backfill because of its high strength and toughness. However, the fiber enhancement and damage mechanism of FRFTF still need to be further explored. The pore crack growth and particle structure distribution features of three kinds of basalt (B), polypropylene (PP), and glass (G) fibers on FRFTF were explored. The porosity, fracture, sphericity, and fractal dimension of FRFTF were quantitatively probed by X-ray micro-computed tomography combined with uniaxial compression (UCS) and SEM, while the spatial distribution of porosity and fracture of FRFTF was analyzed by 3D reconstruction technology. Laboratory findings demonstrate that the porosity of glass fiber increases from 1.46% to 4.74% with the increase of fiber content from 0.3% to 0.9%. This is related to the weak adhesion between the backfill and the fiber. Adding fiber and blowing agents could well enhance the pore distribution and morphology of FRFTF, reduce the number of principal cracks trapped within backfill specimens, and maintain the structure’s integrity. The relationship between FRFTF’s UCS value and porosity/fracture is closely related to the nature and quantity of fibers, and the overall performance of glass fiber is the best among others. As the quality of glass fiber shifts from 0.3% to 0.9%, the fill specimen’s UCS value is adversely correlated with the porosity. In the current study, the internal connection and damage mechanism of FRFTFs are studied microscopically. The combination of macro-mechanical strength and microscopic mechanism provides a new research idea for FRFTF materials during the implementation of the fully mechanized mining technology in hard rock mines.