Determination of mechanical and microstructure properties of paste backfills to avoid to overburden failure.

Backfilling, a widely used technology for green and sustainable underground practice, is an environmentally sustainable engineering approach. This study comprehensively investigates the mechanical properties and microstructural characteristics of backfills maintained underground for three years to avoid overburden failure, considering the static and dynamic mechanical characteristics, creep characteristics, permeability, and microporous structures under dry, natural, and saturated states. The experimental results indicate that the backfill can maintain a high residual stress after peak stress with a very low permeability under triaxial compression. The strength of backfill worked three years under dry, saturated and natural states show a slight difference, indicating a slight water effect on the long-term backfill. The triaxial compression strength of the backfill is greater than the value of stresses in the goaf of panel, indicating that the backfill strength has been achieved an standard value that can support the surrounding rock mass and maintain the stability of themselves in a long term. The porous structure of the backfill show a micro basis for the macro mechanical properties. All the results show that backfills possess the low permeability, strong strength, stable microstructure characteristics under complex environment and indicating an improving function and strength in supporting the surrounding rock mass and maintaining the stability themselves. The findings indicate that the backfills can serve as a useful reference for the control mechanism, waterproof effect, and safety evaluation of the backfill on the deformation of the surrounding rock mass underground. Furthermore, the successful applications show a good verification, indicating a significant practical application in other coal mines with the similar engineering geological conditions, which also contribute to other underground practice. [Display omitted] • The backfill underground can maintain a high residual stress after peak stress. • The saturated backfill has poor resistance to cyclic deformation. • The creep deformation is characterized by 3 stages. • The porous structure reduces the permeability of the backfill. • The network structure makes the pore structure more stable. [ABSTRACT FROM AUTHOR]