For estimating the amount of infiltrated water during heavy rainfall after transition from open-pit mining to underground block caving, the Beiyi mining area of Shilu Iron Mine in Hainan Province after transition from open-pit to underground mining was taken for study. The characteristics of “three zones” formed due to overburden subsidence during the block caving of Beiyi mining area were analyzed based on the field investigation and numerical simulation of land subsidence area. The influence of different overburden on the infiltration coefficient of rainfall was also analyzed with a numerical calculation model for unsaturated overburden. Then, based on the practical measurement of rainfall and drainage, statistical analysis and inverse analysis were conducted for the infiltration coefficient of the caving zone and the surface runoff coefficient. The infiltrated water due to heavy rainfall in Beiyi mining area after transition from open pit from underground mining is calculated to be 225 386 m³, which can provide a reference for the design of infiltration and drainage system for the mine after transition from open-pit to underground mining.

In order to address problems of high cost, high noise and low efficiency of traditional smooth blasting technology, a new charging structure without a detonating cord was proposed, and the parameters were determined according to the requirements of smooth blasting. Tests on smooth blasting without a detonating cord were carried out for blastholes with non-coupling coefficients of 3.8, 3.9 and 4.0, respectively. Based on the analysis of the half-hole rate after smooth blasting, the smooth blasting effects of blastholes corresponding to three non-coupling coefficients were analyzed based on comparison. The results show that each blasthole for smooth blasting can be successfully initiated by using a charging structure without a detonating cord, and the half-hole rates of blastholes are 78.40%, 89.60% and 57.60% respectively corresponding to those three non-coupling coefficients. It is concluded that an optimal non-coupling coefficient of this new smooth blasting technology in the test is 3.9.

An acoustic emission (AE) test of granite under uniaxial step loading was carried out, and the evolution characteristics of AE frequency, event incidence and fractal dimension of the sample at each load-holding stage before occurrence of instability and fracture were analyzed. The results show that the high-frequency signal first decreases and then increases with the increase of stress in the process of step loading; and macro-instability occurs in the sample at the last stage of step loading, at which the internal micro-cracks in the sample undergo from stable propagation to unstable propagation. The incidence of acoustic emission events decreases gradually as time is prolonged. At the last stage of step loading, the incidence of acoustic emission events decreases first and then increases, unstable fracture in the rock increases and micro-cracks gradually merge and coalesce to form macro-cracks, resulting in overall instability and fracture of the sample; with the increase of stress, the fractal dimension of acoustic emission decreases after an initial increase, and the rock fracture develops gradually in an order way from a disorder way.

Based on the triboelectric charging characteristics of the main minerals of quartz, molybdenite and chalcopyrite in a copper-molybdenum ore, the enrichment effect and mechanism of triboelectrostatic separation of chalcopyrite from the mixture under different conditions were investigated. The triboelectric charging results show that after the interaction with the rotary charger under applied electric voltage, chalcopyrite, molybdenite and quartz are remarkably different in charge-mass ratio. In mineral processing tests, a rotary triboelectrostatic separator (RTS) was adopted to treat an artificial ore with chalcopyrite, molybdenite and quartz in a mass ratio of 1∶1∶8. The results show that with the applied voltage of the rotary charger at -14 kV, the charger rotation speed at 5 000 r/min and the co-flow air velocity at 2 m/s, a copper concentrate can be obtained with Cu grade up from 3.3% to 5.9% at Cu recovery of 90%, and with Cu grade up to 9.3% at a recovery of 50%.

Aiming at uncertainty of beneficiation product zone in dry magnetic separation process, an image segmentation method based on an improved U-Net model was proposed by employing machine vision. In this improved model, convolutional block attention module (CBAM) is utilized to enhance the recognition and attention of the network for target areas, which is beneficial to the segmentation of target objects under complex backgrounds; depth-wise separable convolution is adopted to reduce computational complexity while maintaining accuracy, providing strong support for obtaining high-resolution images of beneficiation product zone. Thus, this model can be applied in magnetic separation and also improve network performance. It is found that this improved model can bring segmentation accuracy up to 92.28%, and also is superior to classic U-Net, DeepLabV3+ and PSPNet models in terms of contour extraction completeness and denoising capabilities.

A kind of polymetallic lead-zinc sulfide ore in Guangxi was taken for experimental research. In view of its characteristics of high zinc and low lead, as well as difficulty in the separation between zinc and lead, a new type of efficient inhibitor JFR-1 was adopted in the experiment. It is shown that the lead-zinc sulfide ore was subjected to a lead-zinc bulk flotation, consisting of one roughing, two cleaning and two scavenging, followed by a separation of lead and zinc, consisting of one roughing, two cleaning and two scavenging, finally resulting in a lead concentrate grading 21.00% pb at 72.82% recovery, a zinc sulfide ore grading 6.96% Zn at 94.21% recovery, and a tailings grading 0.04% Pb and 0.13% Zn with a lead recovery of 10.85% and a zinc recovery of 4.79%. Thus, the enrichment and separation of lead and zinc can be actualized.

Acid mine drainage (AMD) and a pulp regulator, TY-308, were used combinedly for activation in flotation of highly alkali-depressed pyrite, in which AMD was used to neutralize the pulp alkalinity, and TY-308 used to reduce the negative effect of AMD on flotation. A closed-circuit test on flotation with the process consisting of one-stage roughing, one-stage cleaning and one-stage scavenging yielded a pyrite concentrate grading 48.73% S at 97.93% recovery. Compared with the practice using sulfuric acid as the activator, the sulfur recovery can be increased by 1.34 percentage points. Furthermore, not only the cost for AMD treatment will be significantly reduced, but the safety risk associated with the use of concentrated sulfuric acid can be avoided.

The effects of sulfuric acid concentration, calcite particle size, sodium dodecyl sulfate (SDS) dosage and flow rate of dynamic fluid on the apparent density of calcite particles during acid reaction were studied. The results show that when the sulfuric acid concentration is 1%, calcite can sustain at the low apparent density state, and the smaller the calcite sizes, the lower the apparent densities. SDS with a concentration of 300 mg/L can enhance the hydrophobicity of calcite, increase effectively the adsorption density and residence time of CO₂ bubbles on calcite, and prolong the duration of low apparent density of calcite. Dynamic fluids may accelerate desorption of gas bubbles from calcite, which is detrimental to the reduction of apparent density of calcite during acid reaction process, but the SDS treatment can significantly reduce this detrimental effect. Settling tests show that acid reaction can prolong the settling time of calcite particles, creating favorable conditions for the separation of calcite and non-carbonate minerals by gravity concentration.

Based on the mineralogy of the high-sulfur sedimentary bauxite ore from Pingguo area of Guangxi, including mineral composition, structural property and mineral dissemination characteristics, three kinds of technical schemes were proposed according to the ore properties, including flotation, reduction roasting plus magnetic separation, and calcination, and then adopted respectively in experiments of desulfurization. The mineralogical study shows that this bauxite ore contains 65.04% Al₂O₃ with S grade of 5.08%, and the dominant minerals therein are diaspore and pyrite. It is found that the pyrite can be effectively removed by those three processing techniques, and the flotation process can yield an bauxite concentrate with Al₂O₃ grade of 75.90% and the S grade reduced to 0.49%, which is qualified as the feed material for the succeeding alumina extraction. In this case, it is recommended that the flotation be selected as a pre-desulfurization solution for high-sulfur sedimentary bauxite ore.

For a cobalt leaching residue grading 1.31% Cu and 0.20% Co, a flowsheet consisting of grinding and a flotation process of one stage of roughing, one stage of scavenging and two stages of cleaning was proposed based on the occurrence of copper and cobalt therein. A closed-circuit test employing this processing technique can result in a bulk copper-cobalt concentrate grading 16.16% Cu and 2.06% Co with recoveries of 80.56% Cu and 68.29% Co, with the yield of 6.63%. It is concluded that with this approach, copper and cobalt resources in the cobalt leaching residue can be enriched and recovered efficiently.