Experimental characteristics for deformation properties of backfill mass

Abstract

Purpose. Determining the deformation properties of backfill mass used to preserve the continuity of the coal-rock stratum enclosing mine workings. Methods. To achieve the purpose set, laboratory studies have been performed on crushed rock samples with different granulometric composition, which are exposed to uniaxial compression in a steel cylinder. The experimental data are processed using the mathematical statistics methods. Findings. As a result of performed laboratory studies, it has been determined that during compression pressure of the backfill material from crushed rock, the deformation modulus is a variable value and depends on the value of the applied load, which means that it cannot be used as a physical characteristic of the backfill mass. It has been proven that the deformation modulus characterizes the backfill mass rigidity, that is, its ultimate stress state. The rigidity value under a constant external load, can be regulated using the granulometric composition of the crushed rock. It has been revealed that the maximum shrinkage of the backfill mass is achieved when repacking crushed rock fractions of different sizes under volume compression of the backfill material. In the case when the backfill material is a homogeneous fraction of crushed rock, when increasing the constrained modulus, the backfill mass rigidity increases, and shrinkage decreases. Originality.It has been proven that the values of the crushed rock compaction coefficient, which characterizes the shrin-kage of the backfill mass, are correlated with a parabola and depend on the granulometric composition of the source material. With inhomogeneous granulometric composition, the compaction coefficient values are maximum, and for backfill material with the similar fraction, they decrease with a change in the bulk density of the crushed rock. Practical implications. To ensure the side rocks stability and to maintain mine workings in an operational state, it is necessary to ensure a uniform by volume granulometric composition inhomogeneity of the crushed rock. This determines the ability of the roof and bottom of the coal seam to effectively respond to the impact of external factors that are manifested in the mass of sedimentary rocks during mining operations.