According to the difficulties in beneficiation, such as intimate dissemination and complicated intergrowth of pentlandite, chalcopyrite and pyrrhotite, and high content of magnesium-bearing silicate minerals, a beneficiation experiment was conducted for a low-grade copper-nickel sulfide ore from abroad. A flowsheet consisting of rough grinding, fine-grinding of middlings, copper-nickel bulk flotation was introduced to treat this raw ore with Ni and Cu grades respectively as 0.50% and 0.20%. Adopting selective grinding approach and using high-efficient depressant CMC, excessive comminution of copper and nickel minerals can be avoided while magnesium-bearing silicate minerals can be selectively depressed. A closed-circuit test produced a copper-nickel concentrate grading 9.70% Ni and 4.75% Cu at corresponding recoveries of 68.99% and 79.85%, indicating copper and nickel resources were all effectively recovered.

In order to study the influences of diameter, length and installation position of tapered pipeline on the ratio of full pipe flow in gravity-fed pipeline transport of backfill slurry, a small-scale loop pipe test was carried out by using independently developed tapered pipeline. The hydraulic slope and ratio of full pipe flow were tested for gravity-fed transport of slurry via tapered pipeline, and Pearson correlation analysis was also conducted to explore the influence of various factors on the ratio of full pipe flow. The results show that the ratio of full pipe flow significantly presents a negative correlation to the diameter of tapered pipeline, which increases exponentially with the reduction in the diameter of tapered pipeline. The ratio of full pipe flow increases sharply for a pipe with diameter less than 50 mm. Furthermore, the ratio of full pipe flow presents a positive correlation to the length of tapered pipeline, which increases linearly with the increased length of tapered pipeline. However, the installation position of tapered pipeline in horizontal section of pipe has little effect on the ratio of full pipe flow, which can be negligible.

In order to improve the construction efficiency in benching excavation for tunnels in water-rich ground, a main tunnel of Xiaomaliu tailings pond was taken as an example in the study. A three-dimensional digital model was constructed according to the actual situation of the project, and the fluid-structure interaction analysis was conducted by simulating benching excavation with three types of bench length. Then, the effect of benching construction with different bench length was analyzed in terms of seepage field, displacement field, stress field and plastic zone distribution of tunnel after construction, and a comprehensive evaluation was presented by using CRITIC algorithm. Results show that excavation with micro bench can bring the best construction effect for the tunnel in water-rich ground, followed by excavation with long bench, and excavation with short bench presents poor effect.

Based on a summarization of decomposition techniques of scheelite by hydrometallurgical process, the advantages and disadvantages of several decomposition techniques, such as decomposition with hydrochloric acid, soda sintering, pressure boiling of soda, decomposition with sodium hydroxide, decomposition with fluorine salt, decomposition with mixture of sulfuric acid and phosphoric acid, as well as lime sintering conversion followed by decomposition with ammonium bicarbonate were all analyzed. It is concluded that those three techniques, including decomposition with fluorine salt, pressure boiling of soda and decomposition with mixture of sulfuric acid and phosphoric acid, will gradually become the mainstream decomposition techniques for scheelite.

A thermodynamic analysis reveals the phase evolution of main metals in the production of low-grade nickel matte by sulfidation smelting of copper-nickel electroplating sludge, and the main influencing factors in the process of sulfidation smelting were analyzed. The thermodynamic calculation shows that with the electroplating sludge grading 6% Cu and 4% Ni, respectively, sulfur gypsum as the sulfurizing agent, the actual addition of sulfur 2.0 times of the theoretical amount, and the smelting atmosphere P(CO)/[P(CO)+P(CO₂)]=50%, the low-grade nickel matter with the expected grade of 57.2% (Cu+Ni) can be produced, with the grade of copper and nickel in the slag lower than 0.2%. It is shown that the direct recovery rate of copper and nickel can reach 99.89% and 96.59% respectively, and the sulfur fixation rate is 77.20%. An industrial application shows that compared with conventional wet metallurgical recovery process, this technique can bring higher metal recovery rate with a green and low carbon process, thus presenting obvious technical advantages.

Effects of Ca²⁺, Mg²⁺, SO₄^2- and PO₄^3- on the flotation behavior and surface properties of dolomite and fluorapatite were studied by performing tests of pure mineral flotation, Zeta potential and contact angle. The results show that dissolved ions can significantly change the floatability, surface electricity property and surface wettability of these two minerals. Ca²⁺, Mg²⁺, SO₄^2- and PO₄^3- can reduce their contact angles, weaken their hydrophobicity and decrease the flotation recovery. Ca²⁺ and Mg²⁺ can increase, while SO₄^2- and PO₄^3- can decrease the Zeta potential of dolomite and fluorapatite. These results can be used as reference for removal of harmful ions in phosphorite ore processing.

Based on a deep foundation pit project for Pazhou Station of Guangzhou Metro, numerical simulation was conducted with FLAC^3D finite element software for foundation pit excavation. Shear test schemes with different stress paths were prepared based on the stress state of the surrounding soil of the foundation pit, and the influence of different stress path on the mechanical properties of the soil was also studied. The results indicate that stress path can bring significant impact to the stress-strain relationship, pore pressure, and shear strength indicators of the soil. The shear strength of the soil in consideration of the unloading stress path of the foundation pit is lower than the shear strength obtained from conventional tests.

In order to improve the working performance of drum cutter in mining mechanism, the cutting process of drum cutter under different working conditions was numerically simulated by using discrete element method (DEM). The effects of cutting thickness, rotating speed and tractor speed on cutting resistance, productivity and specific energy consumption were investigated by single-factor analysis and orthogonal testing. With cutting resistance and specific energy consumption of the drum cutter as evaluation indexes, the best working parameters of the drum cutter were obtained by matrix analysis. The results show that as cutting thickness increases, both cutting resistance and productivity increase, while specific energy consumption decreases. With rotation speed increases, cutting resistance and productivity decrease, but specific energy consumption increases. And with tractor speed increases, both cutting resistance and productivity increase, while specific energy consumption decreases. It is concluded that the optimum working parameters of drum cutter are as follows: cutting thickness of 50 mm, rotation speed of 100 r/min, and tractor speed of 0.06 m/s.

A copper-lead-zinc polymetallic sulfide ore, being characterized by complex dissemination of main minerals and intimate intergrowth of valuable minerals and gangue, was taken for study. In an experiment, the raw ore grading 0.21% Cu, 2.37% Pb and 3.01% Zn was treated with a weak-alkali process, consisting of Cu-Pb bulk flotation, Cu/Pb separation and Zn flotation. With A22 as a copper-lead bulk flotation collector, TZ01 and zinc sulphate as depressants of zinc and sulfur minerals, CZ08 as a zinc flotation collector, sodium sulfite and CMC as depressants for Cu/Pb separation, a copper concentrate grading 22.09% Cu at 70.48% recovery, a lead concentrate grading 59.48% Pb at 89.35% recovery, and a zinc concentrate grading 45.00% Zn at 86.96% recovery were yielded.

Fe-Cr-B based wear-resistant coating was prepared on the surface of 45 steel by ultra-high-speed laser cladding. The effects of laser power, scanning speed and powder feeding speed on the aspect ratio and crack of single pass cladding layer were studied by orthogonal experimental method, and the effects of overlap rates on the surface quality of cladded layer was also studied. The optimal process parameters were determined as follows: laser power of 2 300 W, scanning speed of 250 mm/s, powder feeding speed of 24 g/min, and overlap rate of 70%. The results show that the hardness of the coating is between 754HV_0.2 and 831HV_0.2, which is 2.36 times to 2.60 times of the matrix hardness. Under the same conditions, the volume wear of the coating is only 3.64% of electroplated hard chromium coating.