Study on Mix Proportion Optimization and Microstructure of Coal-Based Solid Waste (CSW) Backfill Material Based on Multi-Objective Decision-Making Model

Abstract

The preparation of underground-backfill material from CSW can be used for large-scale disposal of solid waste. The proportion of backfill material plays an important role in transportation and backfilling effect, and the mix-proportion optimization of backfill material is essentially a multi-factor and multi-objective optimization problem. In this paper, to obtain the mix proportion of backfill materials with optimal comprehensive-evaluation indexes, and suitable for the engineering application, the fluidity and strength of backfill material, mainly composed of coal gangue(CG), fly ash (FA), flue gas desulfurization gypsum (FGD gypsum), and gasification coarse slag (GCS), were tested by single-factor transformation method, and the effects of various solid wastes on the slump-flow, bleeding rate and early strength of backfill material were analyzed. The optimal mix proportion of CSW with the slump-flow, bleeding rate, and 3-day and 7-day strengths as the evaluation indicators is FA: GCS: FGD gypsum: CG = 25%:25%:25%:25%, according to the multi-objective decision model. Furthermore, the comprehensive evaluation index that meets the requirements of mine backfilling is obtained by changing the ordinary portland cement (OPC) content, that is, the optimal OPC content is 10% of the total solid waste, and the mass concentration is 78%. Finally, the pore structure, micromorphology, and composition of the backfill material with the optimal mix proportion were studied by Mercury Intrusion Porosimetry (MIP), X-ray Diffraction (XRD), and Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS). The research results provide a good reference for the field application of CSW for underground backfilling.

Mix proportion and microscopic characterization of coal-based solid waste backfill material based on response surface methodology and multi-objective decision-making

“…It is a multi-objective decision-making model, which is suitable for the comprehensive evaluation and optimization model. In this regard, m indicators are used to comprehensively evaluate n schemes, and a target eigenvalue matrix is established 30,40 :…”

“…Although there also have been research results on the multi-source CSW for underground backfilling in recent years, for example, Zhang et al 27,28 used orthogonal experiments to study the mix proportion and mechanical properties of multi-source coal-based solid waste backfill materials, Wei et al 29 used RSM to study the mix proportions of four types of coal-based solid waste, Zhao et al 30,31 researched on the effects and proportions of four types of multi-source CSW, the current research and application are still not extensive and in-depth enough. Moreover, five kinds of CSW are used to prepare underground backfilling materials, with many types, complex compositions and unknown properties.…”

Physicochemical Properties and Planting Performance of Artificial Soil Developed from Multiple Coal-Based Solid Waste Materials

“…However, this approach does not adequately address the issue of insufficient soil resources for ecological restoration in mining areas. Indeed, it has been observed that CSWM, such as CG and FA [25][26][27], possess abundant mineral constituents such as aluminates, silicates, and oxides of iron and aluminum. These mineral components are close relatives to the natural soil.…”

The Material Mix Proportion of Roadside Backfill Body (RBB) Based on Spatiotemporal Law of Ground Pressure: A Case Study

“…In addition, many literature have carried out research on the mix proportion of different types of backfill materials, such as tailings (Fall et al, 2008), gangue (Feng et al, 2016), waste rock (Fu et al, 2018), multi-source solid waste (Zhao et al, 2022), etc., and various methods have been used, such as response surface method (Wei et al, 2022), BP neural network method (Feng et al, 2021), orthogonal test method (Zhang et al, 2022), multi-objective comprehensive decision-making method (Zhao et al, 2022), etc. However, the above-mentioned researches on the mix proportion of backfill materials are seldom carried out targeted research based on the law of ground pressure behavior, resulting in the lack of precise matching between the obtained mix proportion of backfill material and the temporospatial laws of ground pressure behavior, especially for the mix proportion of roadside backfill materials in the GER.…”