## 6 Conclusions  
1. Experimental results indicate that the cement used contains 54.66% CaO and 21.91% SiO\({}_{2}\), while the fly ash contains 54.91% SiO\({}_{2}\) and 30.19% Al\({}_{2}\)O\({}_{3}\), and the coal gangue contains 52.78% SiO\({}_{2}\) and 20.67% Al\({}_{2}\)O\({}_{3}\). Although coal gangue exhibits slightly inferior physical properties compared to natural crushed stone, its main chemical composition and overall performance still satisfy the technical requirements for use as a concrete aggregate. 2. Based on steam curing tests, the optimal curing regime was established for mixtures containing 20% fly ash by mass of cementitious materials: static curing for 18-24 h, a heating rate of 20 \({}^{\circ}\)C/h, a constant temperature of 50 \({}^{\circ}\)C, and a constant temperature duration of 24 h. This regime effectively activated the early pozzolanic activity of fly ash, significantly enhancing the strength development of the concrete. Orthogonal experiments and range analysis revealed that coal gangue content had the most pronounced effect on compressive strength, followed by additional water content, whereas the maximum aggregate size had the least influence. Under the requirement of achieving a design compressive strength of 30 MPa, the optimal mix proportions were determined to be 20% coal gangue content, 20 mm maximum aggregate size, and 70% additional water content. The results of variance analysis were consistent with those of the range analysis, confirming the rationality and effectiveness of the proposed optimization scheme. 3. The coal gangue concrete specimens exhibited favorable mechanical properties, including an average compressive strength of 32.1 MPa, tensile strength of 2.93 MPa, shear strength of 4.0 MPa, cohesion of 2.7 MPa, internal friction angle of 31\({}^{\circ}\), and a tensile-to-compressive strength ratio of 0.08. The average elastic modulus was 3.5 GPa, Poisson's ratio was 0.23, and the average peak strain was 2.57%. Failure mode analysis indicated that structural failure was primarily governed by the inherent strength limitations of the coal gangue aggregate. Durability testing revealed that compressive strength remained stable under neutral conditions, declined slightly in sulfate environments while maintaining moderate corrosion resistance, and experienced the most severe degradation in acidic (HCI) environments. Conversely, alkaline (NaOH) conditions promoted strength development, suggesting that the material is well-suited for weakly alkaline underground environments. 4. Combined with the geological conditions of 431,304 working face roadways in Liangshuijing coal mine, the pavement structure is simplified into surface layer, cushion sand layer and siltstone base layer. The maximum design load is 0.85 MPa, and the allowable deflection is 0.83 mm ( corresponding to 106 cyclic load life). Based on ANSYS, the finite element model of assembled pavement is established, and the stress and displacement responses under different loads, block thicknesses and dynamic loads are analyzed. The most unfavorable load position is determined to be the middle of the plate edge. The results show that the maximum deflection of the hexagonal coal gangue block with a side length of 20 cm and a thickness of 16 cm is 0.73 mm, which is far lower than the deflection limit and within the required deflection range, so it can meet the requirements of structural stability and bearing performance of underground roadway. In summary, regular hexagonal coal gangue concrete blocks with a side length of 20 cm and a thickness of 16 cm exhibit superior mechanical performance, durability, and structural adaptability, rendering them well-suited for a wide range of underground mine tunnel applications. These blocks offer a practical and cost-effective solution for the efficient installation and maintenance of underground tunnel pavements.