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Liu, et al.

(Statistical Package for Social Sciences [SPSS], IBM, effects (p<0.01 for all factors across responses) and the
United States of America). absence of statistically significant two-way interactions
The initial assumption of negligible interactions was (p>0.05) detected in our dataset. This approach
justified based on: (i) the primary objective of identifying provided an efficient framework for identifying the most
dominant main effects influencing rheology; (ii) the influential parameters controlling slurry behavior. The
established precedent in similar rheological studies orthogonal experimental design is presented in Table 2.
of particulate suspensions using orthogonal arrays for The solid volume concentration of grouting slurries
factor screening; and (iii) subsequent statistical analysis is typically set between 50% and 80%. 9,10 Accordingly,
confirming the overwhelming significance of main this study selected three volume concentrations: 50%,
60%, and 70%. Larger coal gangue particle sizes reduce
grinding costs, while excessively coarse particles may
compromise slurry properties and increase injection
costs. To analyze the influence of particle size on slurry
performance, coal gangue was ground to three particle
sizes: 50, 100, and 150 meshes. In addition, five fly ash-
to-coal gangue mass ratios were selected: 7:3, 6:4, 5:5,
4:6, and 3:7.

2.3. Experimental procedure
The coal gangue was crushed using a grinder and sieved
through 50, 100, and 150 mesh screens. Fly ash and coal
gangue were weighed according to the predetermined
Figure 1. Schematic diagram of the injection process mass ratios and transferred to a temperature-controlled
in separated‑bed grouting mixing vessel maintained at 25 ± 2°C. Deionized water

A B

Figure 2. X‑ray diffraction patterns: (A): Coal gangue, and (B) Fly ash.
Abbreviations: Al O : Aluminum oxide; CaSO : Calcium sulfate; Fe O : Ferric oxide; NaAlSi O : Sodium
4
3
3
8
2
3
2
aluminum silicate; SiO : Silicon dioxide; TiO : Titanium dioxide
2 2
Table 1. Results of X‑ray fluorescence analysis for coal gangue and fly ash
Compounds SiO Al O CaO Fe O TiO MgO P O Na O K O LOI a
2 2 3 2 3 2 2 5 2 2
Coal gangue 50.63 17.31 4.24 7.64 3.36 1.42 1.24 3.31 2.47 8.38
Fly ash 62.31 22.41 3.11 6.04 1.12 0.08 0.14 1.53 1.21 2.05
Note: Mass loss of the sample upon heating to 950℃.
a
Abbreviations: Al O : Aluminum oxide;CaO: Calcium oxide; Fe O : Ferric oxide; K O: Potassium oxide; LOI: Loss of ignition;
3
2
2

3
2
MgO: Magnesium oxide; Na O: Sodium oxide; P O : Phosphorus pentoxide; SiO : Silicon dioxide; TiO : Titanium dioxide.
2
5
2
2
2
Volume 22 Issue 5 (2025) 216 doi: 10.36922/AJWEP025210162