Experimental study on flocculation sedimentation was carried out in a laboratory for the lead processing tailings from a lead-zinc mine, and the flocculant type, flocculant dosage and feed concentration were all investigated. Then, the selected flocculant was applied into a lead-zinc-sulfur flotation. The results show that the anionic PAM flocculant AX868 presents a better sedimentation effect, and its addition into the flotation system leads to the obtained flotation indicators equivalent to those by using clear water. It is found that an addition of 20 g/t AX868 into the thickener with a diameter of 36 m can meet the sedimentation requirements in industrial production.

Random Forest (RF) and eXtreme Gradient Boosting model (XGboost) were adopted to assess the landslide hazard in Changsha City, and frequency ratio (FR) was then used to check and verify the obtained result. A vulnerability assessment system was established based on analytic hierarchy process (AHP) and then adopted to make vulnerability assessment. Finally, efficient risk assessment was realized by integrating the results of hazard assessment and vulnerability assessment with numerical classification method. It is found that RF model is similar to XGBoost model in its evaluation performance, but XGBoost model regulated by FR method can bring a more accurate assessment. Also, the vulnerability assessment has the largest weight value of population density, and high vulnerability areas are mostly concentrated in downtown area and traffic arteries. The areas with relatively higher and high risk account for about 4.6% of the entire study area in Changsha City, which are mainly concentrated in valleys, towns and traffic arteries.

With a water cut-off and slope reinforcement project in Tenglong open-pit mine in Hebei Province as the background, a three-dimensional numerical model was established for finite slope with a retaining wall. Firstly, this numerical model was verified for its validity, and then was adopted in numerical simulation and analysis for the distribution law of earth pressure on the back of wall under translational motion. The results show that as the bench becomes wider, the angle of inclination for sliding surface of finite slope falls down to zero first, and then is gradually increased. When the bench is 9 m wide, the numerical solution of passive earth pressure on the back of wall is almost consistent with the analytical solution in term of its variation rule, which fully verifies the validity of this numerical model. The passive earth pressure presents nonlinear distribution, and the active earth pressure presents convex curve distribution. With both the stability of retaining wall and the construction cost taken into consideration, it is recommended that the slope degree should be set at 30° and the bench should be 9 m wide.

In order to obtain the information of landslide in forest area, a high-resolution digital terrain model was derived from LiDAR point cloud, and the data of landslide in forest area were extracted by Res-Unet network and persistent homology. The Fenghe Experimental Forest in Washington State of USA was selected for study, among which three areas were selected for quantitative analysis. Based on calculation, the extracted data of landslide in the forest area show an average precision of 79.7%, an average recall rate of 70.2%, and average F₁ of 65.5%. The extraction method based on Res-Unet and persistent homology can accurately identify most landslides in the research area. It is shown that by using deep learning and persistent homology, this extraction method can make up for the weakness of traditional remote sensing methods in extracting landslide information in vegetation covered areas, and also provide a technical support for landslide analysis.

An experimental study on mineral processing was carried out for the lean magnetite in M1033 Iron Ore from JISCO. After being crushed with high pressure grinding mill, the ore with a fineness of -0.030 mm 85% was processed using a magnetic separator with the magnetic field strength of 180~220 mT, resulting in an iron concentrate grading 65.18% TFe, with SiO₂ content of 5.21% and Fe metal recovery of 73.20%.

An experiment on dynamic loading at high strain rate was conducted for T4 deformed ZK60 magnesium alloy by means of split Hopkinson pressure bar (SHPB). The experimental results show that the flow stresses of the ZK60 alloy samples increase with the increasing of strain rate. Observation of transmission electron microscopy results indicate that a large number of second phases precipitated in the alloy after dynamic loading. The hardness measurement results show that the hardness of material is elevated from 64.40HV to 93.05HV after dynamic loading at 3 000 s^-1. High-density dislocation is generated within the ZK60 alloy and numerous reinforcing phases (β′₁ and β′₂) precipitated in the matrix during deformation.

Magnetic separation tests were carried out by adopting a pulsating high gradient magnetic separators (HGMS) for low-grade manganese rhodochrosite ores from Yingjiang County of Yunnan Province, with more than 50% passing size of the raw ore finer than -0.019 mm, TMn grade of 6.72% and manganese carbonate content of 84.97%. Based on the laboratory test applying a SLon-100 type cyclic pulsating HGMS, a pilot test was conducted with a SLon-500 type vertical ring pulsating HGMS, by adopting an optimized processing flowsheet consisting of one roughing, one scavenging and a cleaning process of the scavenging concentrate, a manganese concentrate was produced with TMn grade and recovery of 16.77% and 87.61%, respectively.

A technique process to remove impurities of calcium and magnesium from the leaching solution obtained after roasting plus leaching process of a sort of lepidolite was studied, and the effects of several factors on washing effect, including amount of sodium carbonate, solution pH, time and temperature of reaction and washing conditions, were all investigated. The results show that removal rates of calcium and magnesium can reach 99.9% and 93.1%, respectively, by adding sodium carbonate as precipitant at an amount of 2.21 mol/L, with pH of solution at 8.0, temperature of 25 ℃and time of 30 min. Then, the obtained calcium-magnesium residue was washed three times with a liquid-solid ratio of 1∶1, and 5 min for each time. As a result, products of calcium carbonate and magnesium carbonate can be obtained. It is concluded that this process, being simple and stable, can be adopted to effectively remove impurities of calcium and magnesium from leaching solution of lepidolite.

A shear creep test was performed for weak intercalation in order to investigate influence of creep characteristics of weak intercalation on slope stability. The obtained curve from the test was fitted according to Cvisc creep constitutive model, and the creep of slope with weak intercalation was calculated by using finite difference method to analyze the variation in long-term displacement and shear strain increment of the slope. The results show that the weak intercalation has typical creep characteristics. The results obtained from the numerical calculation with Cvisc model are basically consistent with the actual monitoring data. The creep characteristics of weak intercalation cause not only increase in the displacement, but also significant changes in the distribution form and orientation of the overall displacement of the slope, especially greater displacement at the top and in the middle of the slope. As a result, the slope body experiences an increment in the shear strain, which is then expanded and finally tends to stable.

Based on the environmental characteristics of polymetallic nodules mining zone, different lifting modes for deep-sea polymetallic nodules, including continuous line bucket (CLB) system, autonomous submersible shuttle mining system and pipeline lifting system, were analyzed in terms of characteristics and applicability. With eight factors taken into consideration, including maneuverability, dry ore lifting capacity, launching and recovery efficiency, manufacturing and operation costs, suitability for water depth, adaptability to extreme sea condition and seabed disturbance, as well as environmental friendliness, a mathematical model covering multi-dimensional evaluation indices and an adaptability evaluation system were established. Analysis results show that CLB system and capsule pipeline lift system are not suitable for lifting polymetallic nodules, while autonomous submersible shuttle mining system, due to high cost in R & D, is not economically applicable. Due to the improvement in the reliability of underwater equipment and progress in the solution to sealing of heavy medium, pipeline lift system with heavy medium is expected to become a high-efficient lifting mode for deep-sea polymetallic nodules.