Abstract
To reduce the amount of cement used in cemented coal gangue backfill (CCGB, a mixture of coal gangue, cement, fly ash, and water), mechanical and deformation properties of CCGB in which CSFA partially replaces the cement (0, 10, 20, 30, and 40 wt%) were studied. Compressive strength, acoustic emission during uniaxial loading, shear strength, and drying shrinkage were analysed. The compressive strength, shear strength, and drying shrinkage tests were performed at different curing times. The results showed that cemented coal gangue and corn stalk fly ash backfill (CGCAB) presented better performance, and the CGCAB with a 20% substitution rate had the best performance at day 28. Despite having the largest drying shrinkage value, 20% is the best choice for the substitution rate of CSFA. A 20% CSFA addition can enhance the bearing capacity of CGCAB and improve its failure mode, which is of great significance to support the upper overburden load and maintain the surface stability of the goaf.
Highlights
Backfilling mining is widely used to address surface subsidence caused by extensive mining, environmental pollution caused by coal gangue accumulation, and low coal recovery rate under buildings/railways/water-bodies [1, 2]
The cement in Cemented coal gangue backfill (CCGB) was replaced by CSFA at 0, 10, 20, 30, and 40 wt%, and the effects of substitution rates on the mechanical and deformation properties of cemented coal gangue and corn stalk fly ash backfill (CGCAB) were investigated
The cement in CCGB was replaced by CSFA at 0, 10, 20, 30, and 40 wt%, and the effects on the mechanical and deformation properties of CGCAB, including compressive strength, shear strength, stress-strain-acoustic emission, and drying shrinkage, were analysed. e compressive and shear strength tests were performed at the curing age of 3, 7, 14, and 28 days. e acoustic emission test was performed only for day 28. e drying shrinkage test was performed at days 1, 3, 7, 14, 28, 45, 60, 90, 120, and 180. e main conclusions are summarized as follows: (1) At days 3, 7, and 14, the group with a 10% substitution rate showed the highest compressive strength
Summary
Backfilling mining is widely used to address surface subsidence caused by extensive mining, environmental pollution caused by coal gangue accumulation, and low coal recovery rate under buildings/railways/water-bodies [1, 2]. Cemented coal gangue backfill (CCGB) can be used to support overburden and prevent surface subsidence upon transportation through a pipeline to underground goaf [3,4,5]. CCGB can reuse solid waste and reduce landfill area, addressing environmental problems [6]. E CCGB for coal mine backfilling is an engineered mixture of coal gangue, fly ash, cement, and water; and the solids account for 75–85 wt% [7, 8]. Wu et al [9] developed a coupling model to analyse the thermal-hydraulic-mechanical-chemical processes that occurred in CCGB. CCGB still presents many practical issues such as insufficient materials [12], excessive cost [13], and low strength [14]
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