Coal gangue is a waste product commonly produced during coal mining. Using gangue as a replacement for conventional aggregates in shotcrete applied to underground roadways is a feasible approach to promote the resource utilization of gangue solid waste. The mix proportions of shotcrete materials are crucial to the effectiveness of field applications. The aim of this study was to investigate the effects of mix proportions on the mechanical properties of the gangue-based shotcrete material applied to roadways. To achieve this, we conducted experiments to measure changes in the slump under different gangue sizes, mass concentrations, sand contents, and cement contents. The study analyzed the influences of various mix proportions on the conveying and mechanical properties of the gangue-based shotcrete material applied to roadways. The slump and the compressive strength were analysed. The following was concluded: (1) The gangue size and sand content have a similar effect on the slump. As the gangue size and sand content increase, the slurry slump initially decreases and then increases, which is attributed to the plasticity of the aggregates themselves. The mass concentration has a negative correlation with the slump, which is the least sensitive to changes in cement content. (2) The compressive strength of all specimens increases with prolonged curing, reaching its maximum after 28 d under the compressive experimental conditions. (3) This paper analyzed the reasons for better mechanical properties under the conditions of smaller size gangue, higher mass concentration, and higher cement content. It has also examined the reasons for greater compressive strength at 35% sand content. The experimental results of this paper also offer relevant guidance regarding the specific mix proportions of the material of the field gangue-based shotcrete material applied to roadways.

The deep mining of coal resources can lead to surface subsidence, thereby damaging the stability of buildings on the surface; however, this issue can be effectively mitigated through goaf backfilling with coal gangue and other solid wastes. In this study, the technical principles of goaf solid waste backfill mining are illustrated, and the surface movement and deformation patterns under different burial depths and compression rates are examined. Additionally, the monitoring and analysis of the roof subsidence and surface building conditions after goaf solid waste backfill mining are described. The results show that as the burial depth and compression rate increase, the maximum values of the surface subsidence and horizontal deformation gradually decrease. When the burial depth is between 800 and 1200 m, the design value of the compression rate for the goaf should be higher than 79%. The actual measurement results show that the maximum subsidence value of the roof after goaf backfilling is 635 mm, and the compression rate is about 80.8%, which is consistent with the theoretical design value. Hence, surface buildings are little affected by mining activities and are within the safe range for use.

Coal gangue accounts for the bulk of the solid waste produced during coal mining. Conventional gangue disposal methods often fail to meet the requirements of environmental protection regulations, making it necessary to broaden the approach used in the disposal of coal gangue. The research aims to explore the feasibility of using gangue to displace coarse aggregates to prepare underground roadway shotcrete. Key performance indicators, including the slump, compressive strength, and tensile strength of the gangue‐based shotcrete with different mixing proportions, were tested. Influences of factors including the cement content, water‐cement ratio, and accelerator content on the performance of gangue‐based shotcrete were analyzed, the optimal mixing proportion of the shotcrete was determined, and a nonlinear prediction model for the strength of the shotcrete was established. Results show that Group O‐4 has the optimal mixing proportion of gangue‐based shotcrete, that is, the cement content, water–cement ratio, and accelerator content are separately 450 kg·m ⁻³ , 0.55, and 4%. Under that mix design, the slump, compressive strength, and tensile strength are 116 mm, 25.8 MPa, and 2.09 MPa, respectively. A multifactor coupling model was built based on orthogonal test data, and a predictive model for the compressive and tensile strengths of gangue‐based shotcrete was obtained through nonlinear regression and fitting. The research provides a theoretical basis and technical support for the use of solid‐waste coal gangue. Finally, the influences of the particle size of gangue on the performance of the shotcrete were analyzed, and the optimal particle size range of gangue was determined to be 0–10 mm.