To rapidly evaluate the stability of tailings dams in flood season, the safety factor and reliability indices were selected to define the critical state of tailings dams. After unsaturated seepage analysis and limit equilibrium analysis, a safety evaluation method for tailings dams in flood season was proposed based on the Critical Rainfall Pattern Curve (CRPC). An orthogonal test results show that the physical parameters of effective internal friction angle φ′, saturated hydraulic conductivity K_s, V-G model fitting parameter a, effective cohesion c′ of tailings sand, and V-G model fitting parameter n were in a descending order in terms of their influences on safety factor-based CRPC. The parameters of c′, φ′ and K_s mainly control the horizontal variation of CRPC, while the parameters of a and n dominate its vertical variation. On this basis, φ′, K_s, a and c′ are selected to establish the reliability index-based CRPC. Parameter analysis results indicate that the area of the stable region of the reliability index-based CRPC gradually decreases with the increase of the coefficient of variation (COV) of c′, φ′, K_s and a, among which the COV of φ′ exerts the most significant impact. Based on the measured rainfall records in flood season, two types of CRPC were adopted to assess tailings dam stability and early-warnings were provided. Based on comparison with the statistical data from local safety monitoring departments, it is recommended that the safety factor-based CRPC method be adopted when the statistical characteristics of soil parameters are unknown.

For the Shandong Xinhui Gold Mine, 20 joints and fractures in rock mass were scanned and measured by using the ShapeMetriX 3D system, and the rock mass occurrence and geometric data of joints were obtained. Then, three traditional stability classification systems (BQ classification, Q classification, and RMR classification) were adopted to evaluate the rock mass stability, and fractal theory was introduced to analyze the spatial distribution characteristics of joints. The results show that rock mass quality is evaluated as relatively the same grade by three classification methods, with the overall stability rated from average to poor. Specifically, the stability of the hanging wall and its contact zone is basically rated as grade Ⅳ or above; the ore body stability is mainly rated as grade Ⅲ; the stability of the surrounding rock of footwall is rated as relatively good, with some as grade Ⅱ. The rock mass with fractal dimension less than 1.1 is good in quality; while the rock mass with fractal dimension more than 1.1 is poor in quality. Based on the above research results, a rock mass quality evaluation scheme with the fractal dimension of joint fracture distribution as the classification index is primarily proposed.

Due to discontinuousness and incompleteness of point cloud data of potential unstable rock mass in high and steep slopes acquired from scanning equipment, there exist large errors in the extracted curvature feature of slopes and boundaries between unstable and stable rock mass are also blurred. To address those problems, a method for identifying unstable rock mass in high and steep slopes based on point cloud 3D reconstruction is proposed. Kriging interpolation is used in processing sparse or unevenly distributed point cloud data. More continuous and complete point cloud data can be obtained by increasing the density of data points in consideration of spatial correlation, so as to accurately reflect the real geometrical configuration of the slope. The normal vectors and curvatures of the point cloud data are estimated by adopting local surface fitting and k-neighborhood search algorithm, so as to extract the geometric features of slope and reveal the slope morphology and potential unstable areas. The inconsistency index is used to analyze the changes in the geometric features of point cloud data, and a threshold is set to screen edge points, thereby the region with unstable rock mass can be accurately delineated after the boundary between unstable and stable rock mass is clearly defined. The point cloud data within the boundary of the unstable rock mass are obtained by incremental Voronoi diagram, and then a 3D model of point cloud data is constructed for the unstable rock mass, and the risk level of the unstable rock mass is also analyzed with the Slide software. This is the whole identification process for unstable rock mass in high and steep mine slopes. The practical engineering application of this identification method shows that the slope curvature can be estimated with an error less than 0.3%, and the calculated F1 scores in identification of unstable rock mass in each group of slope all remain above 0.99, indicating that such method can bring high quality identification of unstable rock mass.

To investigate the mechanical response of argillaceous weathered dolomite and its effect on engineering stability, the weathered dolomite from a mining area was taken for research. Laboratory tests including uniaxial compression, uniaxial splitting and conventional triaxial compression were carried out to systematically analyze its mechanical properties and failure modes under different stress paths. The results show that: Compared with non-argillaceous weathered dolomite, the compressive strength and tensile strength of argillaceous weathered dolomite decrease significantly, while the deformation capacity is enhanced; the compressive strength of weathered dolomite decreases obviously under water-bearing conditions, and argillaceous weathered dolomite is more sensitive to water; in triaxial compression tests, the increase of confining pressure can effectively improve the strength and toughness of rock; argillaceous weathered dolomite is prone to plastic deformation and shear failure, whereas non-argillaceous weathered dolomite tends to brittle failure under high confining pressure.

Aiming at the mechanical characteristics of backfill in high-level stopes of Zhongguan Iron Mine in Hebei Province, analytical models for lateral pressure, shear stress and vertical stress of high-level stopes were established, and the influence laws of stope width, height and length on the stress distribution of backfill were clarified. A strength design model for backfill in high-level stopes with stress distribution taken into consideration was proposed, and the reliability of the model was verified through engineering application. The results show that the lateral pressure reaches the maximum at the bottom of the backfill on the side contacting uncemented or low-ratio cemented backfill; the shear stress increases first and then decreases, peaking at the middle of the backfill, and is significantly affected by stope width and height; the vertical stress of backfill increases linearly with stope length; when the stope length exceeds 45 m, the influence of exposed height on vertical stress becomes gradually prominent. Based on the comprehensive consideration of the stress distribution characteristics of backfill, the shear force at the contact surface of the surrounding rock and the included angle of the horizontal plane, three types of backfill strength design models were constructed. In combination with the working conditions of Zhongguan Iron Mine, a differentiated strength design scheme was selected. Industrial tests on site have verified the accuracy and reliability of the proposed backfill strength design model.

To address the problem of discharged overflow carrying coarse particles during classification of high-concentrated and coarse-grained ores with a large-scale hydrocyclone (Φ838 mm), it was proposed that the cone section of a hydrocyclone was truncated and an annular flat bottom was constructed. Using computational fluid dynamics (CFD), a systematic study was conducted on the influence of different ring width of that annular flat bottom on the hydrocyclone separation performance. The results show that when the ring width increases from 0 to 50.28 mm, the yield of extremely coarse particles within the size fraction (+212 μm) in the hydrocyclone overflow decreases from 49.97% to 28.08%, and the yield of particles within the size fraction (10-212 μm) increases from 40.64% to 57.80%. A scaled-down hydrocyclone model (Φ100 mm) was fabricated based on the similarity principle, and laboratory tests were carried out with it. It is found that in variation of the separation performance of the Φ100 mm hydrocyclone with the ring width of annular flat bottom is highly consistent with the simulation results of the Φ838 mm hydrocyclone. This has verified that the classification of high-concentrated and coarse-grained ore, a hydrocyclone with its conical section structured with an annular flat bottom can effectively prevent overflow of coarse particles and increase the percentage of particles within the effective size fractions.

The finely disseminated hematite-magnetite ore with a TFe grade of 34.31% from Hunan was taken in a research, and a process of rough grinding followed by low intensity magnetic separation (LIMS) was adopted to separate magnetite from hematite. The roughing concentrate was then subjected to regrinding and two-stage cleaning to obtain magnetite concentrate. And the obtained LIMS tailings were then subjected to regrinding, high intensity magnetic separation (HIMS) and reverse flotation for purification, generating hematite concentrate. Based on condition tests, a whole-process test was carried out, producing a magnetite concentrate grading 62.08% TFe at 22.75% recovery, and a hematite concentrate grading a 65.22% TFe at 47.87% recovery. The total iron concentrate was obtained grading 64.17% TFe at 70.62% recovery, and the contents of harmful elements P and S were lower than 0.05%. It is shown that this processing technique can achieve comprehensive recovery of hematite and magnetite through staged grinding and the separation between magnetite and hematite. The produced concentrate has its indicators up to the follow-up requirements for iron-making raw materials.

Mineralogical characterization and flotation tests were carried out for the lithium-bearing mica in a granitic pegmatite-type lithium ore from Xinjiang. It is found that lithium-bearing mica is similar to gangue minerals of albite and quartz in terms of surface properties, and also presents close mineral dissemination characteristics. On this basis, a self-developed high-selectivity collector GYMR was adopted in a closed-circuit flotation process, consisting of one stage of roughing, two cleaning and two scavenging, to achieve efficient separation of lithium-bearing mica with grinding fineness of-0.074 mm 75.20%. Finally, a lithium-bearing mica concentrate grading Li₂O 2.65% at 15.22% recovery was obtained from the closed-circuit flotation test. It is confirmed that the GYMR collector has remarkable advantages in selective adsorption of fine-grained lepidolite and gangue minerals.

The development process of ultra-large SLon magnetic separators was systematically reviewed, with emphasis on technological innovations and industrial applications. It aims to provide technical support for the efficient recovery of complex mineral resources and a reference for the development of smart and green mineral processing equipment. The ultra-large models such as SLon-5000, SLon-6500 and SLon-8000 exhibit significantly enhanced processing capacity and a remarkable reduced unit energy consumption. Industrial application results show that when SLon-5000 is used for the recovery of vanadium-titanium magnetite tailings, a concentrate with a TiO₂ grade of 12% can be obtained, with annual electricity saving of 3 000 000 kWh per unit.

An experimental research was carried out on mineral processing of a skarn-type low-grade copper-lead-zinc polymetallic sulfide ore from the southwestern Yunnan under low-alkali conditions. In view of the ore characteristics, such as multiple valuable elements, fine dissemination and uneven distribution of useful minerals, a low-alkali processing technique consisting of copper-lead bulk flotation, Cu/Pb separation, and zinc flotation was proposed. With the combined reagents of Z200 and BK906 as the collector for copper-lead bulk flotation, a combination of zinc sulfate, sodium sulfite and sodium sulfide as the depressant, sodium sulfide combined with activated carbon as the reagent removers for copper-lead concentrate, BK902 as the lead collector and BK520 as the copper depressant in the Cu/Pb separation, copper sulfate as the activator in zinc flotation and BK906 as the zinc collector, a closed-circuit test produced a copper concentrate grading 24.05% Cu at 88.18% recovery, containing 2.54% Pb and 188.00 g/t Ag, a lead concentrate grading 75.55% Pb at 81.08% recovery, containing 2.57% Cu and 1 410.00 g/t Ag, and a zinc concentrate grading 52.21% Zn at 90.47% recovery, respectively.