In deep mines, two urgent problems are a high temperature thermal environment and solid waste. Filling the goaf with slurry mixed with ice grains is an effective way to solve these two problems simultaneously. The thermal property and mechanical property of the ice-added backfill have a great influence on the cooling effect in the deep mine. In this study, an experimental facility for measuring the temperature distribution of ice-added backfill slurry was established, and the temperature of backfill slurry with different proportions was measured. Then, the thermal properties of temperature distribution and cooling capacity and the mechanical property of uniaxial compressive strength of the backfill specimens were analyzed, and the results indicated the following: firstly, the cooling capacity of ice-added backfill specimens is negatively related with the slurry concentration C and is positively related with the ice-water ratio Ω; secondly, the strength of backfill specimens is affected by the slurry concentration C and ice-water ratio Ω by a contrary law compared to the cooling capacity; thirdly, ice-added backfill slurry with an ice-water ratio Ω of 1:1 has the best mechanical property after solidification. The effects of the slurry concentration and ice-water ratio on the thermal and mechanical properties were analyzed, and the results indicated that the optimum proportion of ice-added backfill slurry is a slurry concentration of 74% and an ice-water ratio of 1:1 in the present research range. This study is significant for the deep mine cooling method with ice-added backfill.

Considering the deep mining heat‐hazard problem, the concept and academic idea of cold load and storage (CLS) functional backfill applied on deep mine cooling was put forward. Firstly, according to characteristics of filling mining, a method of cooling stopes with CLS phase changing backfill which is made from the backfill material with CLS phase change material (PCM) was proposed. The working process, cooling physics, and the economic and safety benefits of CLS phase changing backfill were produced. Secondly, the theory system of cooling with CLS phase changing backfill was built. The theoretical basis of the key problems involved was investigated and analyzed which concluded heat transfer, fluid mechanics, and backfill mechanics. Lastly, the technology system of cooling with CLS phase changing backfill was established on the basis of the required technical assistance. It includes four parts: the backfill material design, the backfill material conveying way design, the stope temperature control scheme design, and the strength of cemented tailings backfill analysis. The idea of applying CLS phase changing backfill on cooling deep mine stopes and its theory and technology systems provide a scientific research and suitable development direction for deep mine cooling.

In view of high ground stress, high geothermal temperature, and thermal hazard during deep mineral resource exploitation, the concept of phase-change heat storage backfill was put forward in this study. Further, the corresponding technical system was constructed and the main content involved in technical system, which is the optimized proportion of the backfill slurry added with phase-change materials (PCMs), was examined. Moreover, we elaborated upon the collaborative optimization of a backfill body’s mechanical and thermal properties and the mutual cooperation on backfill mining, geothermal energy exploitation, and simultaneous stope cooling. The heat transfer behavior of a backfill body plays a key role in technology system. We numerically simulated the heat transfer among a backfill body, surrounding rock, and airflow in the heat storage process, as well as the heat transfer between backfill body and cold fluid during the heat release process. The temperature distribution of a backfill body at different heat storage/heat release times—i.e., the temperature distribution and its evolution—with heat transfer were revealed and analyzed. This study can provide theoretical guidance for a phase-change heat storage backfill, as it has an important significance for the collaborative exploitation of mineral resources and geothermal energy.

A sensitivity study was conducted for three typical expander-based transcritical CO₂ cycles with the developed simulation model, and the sensitivities of the maximum coefficient of performance (COP) to the key operating parameters, including the inlet pressure of gas cooler, the temperatures at evaporator inlet and gas cooler outlet, the inter-stage pressure and the isentropic efficiency of expander, were obtained. The results showed that the sensitivity to the gas cooler inlet pressure differs greatly before and after the optimal gas cooler inlet pressure. The sensitivity to the intercooler outlet temperature in the two-stage cycles increases sharply to near zero and then keeps almost constant at intercooler outlet temperature of higher than 45 °C. However, the sensitivity stabilizes near zero when the evaporator inlet temperature is very low of −26.1 °C. In two-stage compression with an intercooler and an expander assisting in driving the first-stage compressor (TEADFC) cycle, an abrupt change in the sensitivity of maximum COP to the inter-stage pressure was observed, but disappeared after intercooler outlet temperature exceeds 50 °C. The sensitivity of maximum COP to the expander isentropic efficiency increases almost linearly with the expander isentropic efficiency.

This study systematically studied the moisture characteristic curves, water‐holding capacity, and infiltration performance of different particle sizes of gangue in Nanliang coal mine and Dahaize coal mine by comprehensively using numerical simulation and measured data. The HYDRUS model was used to fit the measured moisture characteristic curve, determine the relevant soil parameters, and perform numerical simulations through the set boundary conditions to verify the reliability of the model. The results show that as the particle size of the gangue increases, the saturated water content gradually decreases, and the gangue with a smaller particle size exhibits a superior water‐holding capacity. In terms of wetting front migration, the migration distance of gangue with different particle sizes changes with time in a power function relationship, and the migration speed of gangue with a particle size of 1.25–2.5 mm is the fastest. Infiltration experiments show that gangue with a smaller particle size has a higher infiltration rate and a longer saturation time. The influence of coal gangue particle size on the water retention capacity and permeability of coal gangue is greater than the influence of coal gangue type on the water retention capacity and permeability of coal gangue. The gangue of Nanliang coal mine shows significant advantages in moisture characteristics, and its water‐holding capacity and infiltration performance are significantly better than those of Dahaize coal mine. This study systematically quantified the effects of different particle sizes of coal gangue on soil water retention characteristics, providing a new theoretical basis for its application in soil improvement. By combining numerical simulation and measured data verification methods, the accuracy and reliability of the research results were improved, providing an important reference for similar studies in the future. In addition, the significant effects of coal gangue particle size on soil wetting front migration speed and profile water content were revealed, providing new insights and basis for optimizing water resource management strategies.