Rockburst is one of the major problems in rock underground engineering and mechanics. To make a risk assessment of rockburst and improve the mine safety index, some evaluation systems for rockburst propensity have been proposed and applied, and progress has been made in the study of high-value mines and single evaluation systems, but these evaluation systems are still immature for deep low and medium grade phosphate mines with more complex influencing factors. Therefore, to solve this problem, this study takes the phosphate mining area of the Sujiapo phosphate mine as the main research object, and combines the characteristics of the deep rockburst of the phosphate mine and its physical and mechanical properties; the evaluation system combines fuzzy mathematical method and multiple evaluation methods to determine the propensity of rockburst of deep mining of Sujiapo phosphate mine. The JSM-500LV SEM and acoustic emission results are used to analyze the microscopic mechanism of rockburst from the morphology and composition of the rocks, and the rationality of the evaluation system is further demonstrated. The study shows that dolomite and phosphorite in the study area are moderate rockburst, and shale has a weak rockburst tendency; because the roof dolomite and phosphorite crystallization degree are higher, the elastic modulus is large. Under the action of external load, the roof dolomite stored more elastic strain energy. Deformation damage consumes less energy. The energy released to the outside world after the damage is large, more likely to occur brittle damage, and the rockburst tendency is high. Therefore, the evaluation system combining multiple evaluation methods can comprehensively determine rockburst in phosphate mines.

The study of pore structure in low-permeability sandstone uranium deposits has become a key factor in the profitability of uranium mining. In this paper, pore and fracture distribution in the target sandstone were determined by using mercury injection parameters. Single and multi-fractal models are used to calculate the heterogeneity of pore and fracture volume distribution. Moreover, the correlation between compressibility and the heterogeneity of pore distribution has been studied. The results are as follows. (1) All the samples can be divided into three types by using maximum mercury injection volume and mercury withdrawal efficiency. Type A is represented by a lower maximum mercury injection volume (less than 0.5 cm³·g⁻¹) and a higher mercury withdrawal efficiency (larger than 25%). The volume percentage of pores whose diameter is less than 100 nm and 100~1000 nm in type A samples is larger than that of type B and C samples since in this type of sample, micropores are developed. (2) The fractal dimension value assessed using the Menger model has a good linear relationship with the thermodynamic model, which indicates that the abovementioned models have good consistency in characterizing the pore distribution of tight sandstone. Multi-fractal results show that the lower pore volume in the selected samples controls the heterogeneity of pore distribution in the overall sample. (3) As the effective stress increases, the permeability damage rate gradually increases in a power exponential equation. The correlation between porosity and compressibility is weaker, indicating that only a portion of the pore volume in the sample provides compression space. As the pore volume of 100~1000 nm increases, the compressibility decreases linearly, indicating that pore volumes larger than 1000 nm provide compression space for all the selected samples.

Developing green mining technology for medium-to low-grade mines requires achieving minimal or no damage to the mining area’s ecological environment. A medium-to low-grade phosphate mine in Hubei Province was taken as the research object in this study. The tailings were selected as the main filling aggregate. Indoor tests and theoretical analysis were conducted to analyze the influence of curing age, the water–cement ratio, the cement–sand ratio, and slurry concentration on the strength of the cemented backfill. Furthermore, a multi-factor non-linear mathematical model of the strength of the cementitious filler was established. The study results indicated that the strength of backfill increased linearly with the increase in the curing age, decreased negatively with the increase in the water–cement ratio, and increased exponentially with the increase in the cement–sand ratio and the slurry concentration. The multivariate non-linear prediction model of the strength of the filling body at different ages was also established based on the test results. This predictive model could effectively predict the strength of the cemented backfill, and the error value was not larger than 4%. Our research results can lay a theoretical foundation for developing medium-to low-grade phosphate mine filling with tailings as the main filling aggregate.