Experimental study on the mechanics and deformation failure characteristics of multi-source coal-based solid waste cemented backfill

Objective In order to study the mechanical properties and deformation failure laws of multi-source coal-based solid waste cemented backfill (CBSWCB), the uniaxial compression, acoustic emission response and microstructure test experiments were carried out with 5 types of typical coal-based waste. Methods The factors influencing the uniaxial compressive strength of CBSWCB, as well as their interaction, were analyzed, and a four-dimensional spatial visualization model of the factors influencing the compressive strength based on their interactions was established. Besides, the mechanical evolution characteristics and macroscopic deformation failure laws under uniaxial compression conditions were elaborated by referring to the acoustic emission and microstructure characteristics of CBSWCB. Further, the hydration mechanism of CBSWCB during the loading process and the macroscopic and microscopic relation were demonstrated from the microscopic point of view. Results and Conclusions The test results show that: (1) Mass fraction is the main factor influencing the uniaxial compressive strength, while the blending amount of furnace bottom slag has the least influence. (2) Under the uniaxial compression, the macroscopic deformation failure of CBSWCB transforms from plastic and weak splitting failure to brittle and shear failure. (3) The evolution of acoustic emission parameters of CBSWCB specimen can be divided into the rising stage, the quiet stage, the active stage and the stable stage. the cumulative ring count curve of acoustic emission shows an obvious "step-like" increase trend, with slow increasing in the rising and stable stages, sharp increasing in the active stage, and gradual leveling-off in the stable stage. (4) The low cement dosing and property difference of multi-source coal-based solid waste cemented backfills result in limited hydration, and the low number of hydration products is the main reason for the generally low uniaxial compressive strength of CBSWCB. The research results could provide a certain reference basis for the use of multi-source coal-based solid waste in cut-and-fill mining.