Pore fractal characteristics of fiber-reinforced backfill based on nuclear magnetic resonance

To investigate the pore fractal characteristics of fiber-reinforced backfill, uniaxial compression tests and nuclear magnetic resonance (NMR) tests were conducted on reinforced backfills with different cement-tailing ratios (1:6, 1:8, and 1:10) and different fiber types (polyacrylonitrile fiber and glass fiber). The relationship between the pore size distribution, elastic modulus, uniaxial compressive strength, and cement-tailings ratio of the backfill was investigated, and the pore fractal dimensions of three types were quantified. The results showed that the peak signal amplitude and total spectral peak area of the fiber-reinforced backfill were highest reduced by 21.2% and 25.3%, respectively, compared with that of the fiber-free backfill. The uniaxial compressive strength and elastic modulus of the backfill specimens decreased with decreasing cement-tailings ratio. The micropore fractal dimension values of the backfill specimens ranged from 0.30 to 1.00, while the mesopore and macropore fractal dimension values were in the range of 2.96 to 3.00. The correlation coefficients of the mesopore and macropore fractal dimensions of the backfill are >0.94, and the fractal dimension of mesopores and macropores was not significantly correlated with the cement-tailings ratio and fiber type. The results can provide a reference for discussing the relationship between the microscopic pore structure and macroscopic physical parameters of fiber -reinforced backfill.

Automated summary

Uniaxial compression tests and NMR tests were conducted to investigate the pore fractal characteristics of fiber-reinforced backfill with different cement-tailing ratios and fiber types. The results showed a reduction in signal amplitude and spectral peak area for the fiber-reinforced backfill compared to the fiber-free backfill. The compressive strength and elastic modulus decreased with decreasing cement-tailings ratio. The fractal dimensions of micro, meso, and macropores were quantified and showed no significant correlation with the cement-tailings ratio and fiber type.