A core of uranium deposit was taken in an experiment of column leaching with alkaline solution (NaHCO₃+H₂O₂), and then the surface characteristics and pore distribution of sandstone-type uranium deposit were analyzed by using scanning electron microscope images. The variation in the microscopic pore structure of uranium-bearing sandstone in alkaline in situ leaching process was characterized by using T₂ spectrum of nuclear magnetic resonance (NMR). The results show that the matrix in the core firstly becomes connected pores due to chemical dissolution of leaching solution, resulting in more pore throats among large and small pores. The Al(OH)₃ mineral colloid and CaCO₃ generated by the reaction are deposited intensively in the pores and microcracks, which reduces the effective reaction area between leaching solution and matrix, thus reducing the uranium leaching efficiency. During the period of 97-158 h, dissolution is predominant, leading to the amount of chemical dissolution much higher than the amount of precipitation and accumulation, thus forming a large number of connected pores. Further reaction and dissolution of uranium minerals in the leaching solution can increase the recovery of uranium mineral to the peak.

With a transport roadway at+392 m section of №92 ore body in Tongkeng Mine as an example, the testing area was firstly divided for investigating the required on-site data. Then, the roadway roof rock was scored by using mining rock mass rating (MRMR) system for rock quality classification and rating. Finally, an appropriate support measure was proposed for the roadway roof based on the grading result. It is shown that the roof rock mass has its score of 50 by RMR system and is rated to be Grade Ⅲ. However, with the modified MRMR system, the rock mass has its score of 29 and is rated to be Grade IV. Compared with the on-site actual investigation of structural plane, the rating result by using MRMR system is much more consistent with actual situation.

By establishing a particle flow model of geological profile with discrete element software PFC^2D, the formation and development process of overlying strata cracks during the mining of ore body were studied, and the mechanism for overlying strata gradually developing into collapse and caving was also revealed. It is found that with the mining of ore bodies, fractures grow upward and increase in numbers. The goaf after mining can cause the overlying strata with tensile-shear failure, and also the new cracks will constantly occur in the strata. Tensile fractures predominantly develop in the overlying strata, but tensile fractures occur at the both ends of fracture development region. Also, more and more concentrated fractures grow upward at both ends of goaf, presenting a potential of gradual collapse and caving of goaf roof. After the third and fourth stratified ore bodies are mined out, roof collapse will take place locally and then gradually develop into roof caving of the whole goaf, finally leading to roof collapse to the surface and forming a small sinkhole on the ground surface. Then, the development progress of sinkholes can be subdivided into stable stage, slow-progress stage, rapid-progress stage and end of progress in terms of the numbers of fractures, presenting the mechanism for overlying strata developing from tensile fracture and shear fractures at both ends of goaf to overall collapse.

In order to study the energy distribution of blast wave propagation, the EEMD and Hilbert transform techniques were adopted to analyze the blast vibration signals at the same measuring point in different directions, on the same line with different distance away from explosion center, as well as with the same distance away from explosion center but with different maximum charges. It is found that vertical signal energy is mainly concentrated in the midbands, while the radial signal energy in horizontal direction is distributed in both the mid- and low-bands, and tangential signal energy in the horizontal direction is mainly concentrated in the high-bands. Under the same monitoring, a greater attenuation is found in high frequency energy and the proportion of signal energy distribution shifts from high-bands to low-bands as the distance is farther away from the explosion center. However, with the same distance away from the explosion center, increasing the maximum charge in a single stage can lead to higher proportion of low frequency energy, and significantly increased charge can bring more obvious effect.

The progress in the research of micro-fine mineral flotation process is reviewed in terms of grinding, pulping, separation, and finally a prospect for the research direction of micro-fine mineral flotation process is presented.

Pure quartz and pyrite minerals in the size range of 5-30 μm were taken in an experiment on viscosity under different pulp temperature and concentration conditions, for investigating the viscosity variation law of ultrafine particles. The results show that the viscosity for both minerals within the same size range increases along with the increase of pulp concentration, and the finer the particle, the greater the increasing rate. Furthermore, the viscosity variation of quartz is more remarkable．With the same pulp concentration, the viscosity of both minerals displays a declining-ascending trend as the temperature rises, which is more significant for finer minerals. The regression analysis shows that the correlation between viscosity and concentration of quartz and pyrite slurry are in line with the exponential fitting model. According to this analysis, the pulp concentration for ultrafine grinding should not exceed 40% and the optimum pulp temperature should be regulated at 50 ℃, which is beneficial for improving grinding efficiency.

The influence of Ce³⁺ in the sodium oleate system on the flotation of fluorite and calcite was investigated by flotation test, zeta potential measurement, solution chemistry study and X-ray photoelectron spectroscopy analysis. The results reveal that in the sodium oleate system, Ce³⁺ with a low concentration exists on fluorite surface in the form of CeF₃·0.5H₂O(s) under acidic and neutral conditions, therewith, fluorite can be activated to generate more active sites for the adsorption of sodium oleate. Meanwhile, Ce³⁺ can be adsorbed onto calcite in the form of Ce₂ (CO₃)₃·8H₂O(s). There are more active sites generated as well, but calcite may be depressed as the hydrophilic nature of Ce₂ (CO₃)₃·8H₂O(s) and the spatial site barrier effect of crystalline water hinder the adsorption of sodium oleate. In alkaline pulp, Ce³⁺ is mostly precipitated to form Ce(OH)₃(s) and depresses both fluorite and calcite as Ce(OH)₃ (s) can consume sodium oleate and reduce its adsorption on both minerals.

Aiming at the commercial production problems in the usage of high-temperature reagents for the reverse flotation in Qidashan Concentrator, a new laboratory-prepared combined collector (AG-1) was adopted in the reverse flotation of mixed magnetic concentrate at room temperature (20 ℃). The results show that a reverse flotation flowsheet consisting of one stage of roughing, one stage of cleaning and three stages of scavenging, with pulp pH of 11.5, the dosages for depressant (corn starch), activator (CaO) and collector (AG-1) at amount of 950 g/t.100 g/t and 750 g/t, respectively, can yield an iron concentrate grading 68.13% TFe at 88.43% recovery. XRD patterns and optical microscopy visualization of flotation concentrate and tailings show that AG-1 has good selectivity, and can effectively separate valuable minerals from gangue mineral of quartz. Compared with the single collector of sodium oleate or dodecylamine, AG-1 possesses a lower surface tension and a stronger ability in reducing the surface tension of gas-liquid interface, which can better improve mineral hydrophobicity.

A flotation experiment was performed with medium grade siliceous and calcareous collophanite from Guizhou Province for determining the optimum technical process and reagent system. With the process flow consisting of three roughing, one cleaning and one scavenging, a high quality phosphate concentrate grading 34.07% P₂O₅ at 75.38% recovery was finally obtained. The adsorption behavior of collector SGC-01 on the apatite surface during the direct flotation process was also investigated by using Zeta potential, infrared spectrum and QCM-D. The results show that SGC-01 can be chemically adsorbed onto apatite in various forms, and presents a better flotation performance compared with sodium oleate.

By performing settling rate test, turbidity test, zeta potential measurements, solution chemistry study and extended DLVO theoretical analysis, the mechanism for sodium hexametaphosphate (SHMP) to disperse ultrafine potassium feldspar and hematite was investigated. It is shown that, Na_m (PO_3)n^m-n (m<n) anions derived from SHMP ionization can wrap around mineral grains in a form of spiral long-chain polymers, forming thick hydrophilic macromolecule protective films. Meanwhile, HPO₄^2-formed by hydrolysis can be adsorbed onto ore grains, leading to decrease of the surface potential and increase of the interparticle electrostatic and steric repulsions. In this case, mineral particles need to overcome a higher potential barrier to reach a stable condensed state. Therewith, the non-selective agglomeration of ore particles weakens, resulting in a significant improvement in dispersion stability.