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.

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.

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.

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.

The action and mechanism of copolymer of maleic acid and acrylic acid (PMAA) in flotation separation of barite and fluorite in the presence of collector of sodium oleate were studied. A single mineral flotation test shows that sodium oleate has a good collecting for barite and fluorite, and PMAA has an obvious selective depressing effect on fluorite. A flotation test of artificially mixed minerals confirms that PMAA can achieve the separation of barite from fluorite in the presence of sodium oleate. A Zeta potential test shows that PMAA can hinder the adsorption of sodium oleate on the surface of fluorite, but cannot hinder its adsorption on barite surface. An XPS analysis shows that PMAA isn't effectively adsorbed on the surface of barite, but is chemically adsorbed on the surface of fluorite through the interaction between carboxyl groups of PMAA and calcium ions of fluorite, thus achieving the selective depression of fluorite during the flotation of barite with sodium oleate.

A nine-hole cut blasting method was adopted in a test of Tonglushan stope. In combination with on-site actual situation, cutting blasting with medium hole length was studied by using theories of compensated space and fissure zone. The first circle of blasthole layout for cutting blasting was optimized, and four types of models for first circle of blasthole layout were then established by LS-DYNA software. After simulation calculation, the rock blasting effect was simulated by using RHT constitutive model. The results show that the more number of empty blastholes (that is, the larger the compensation space), the better the blasting effect in cutting area. The uniformity of empty blasthole position (that is the uniformity of compensative space) will also influence blasting effect. It is shown that both the section and height of the trench after blasting in the field test meet the design requirement, which proves that the first circle blasthole layout for cutting blasting is reasonable.

In order to improve accuracy in selection of blasting parameters for open-pit mines, a mathematical model was established for determining bench blasting parameters in open-pit mines based on production cost of stope, and the blasting parameters were then optimized by using an improved sparrow search algorithm. The results show that the improved sparrow search algorithm can effectively improve the effect of bench blasting in open-pit mine, but also improves the construction efficiency. With Yulong Mining Industry Company in Xizang as an example, the blasting parameters after optimization are as follows: hole spacing of 6.2 m, row spacing of 4.9 m, and unit explosive consumption of 0.32 kg/t. With these blasting parameters, the stope production cost goes down by 7.5% to 11.06 yuan/t, and the bulk rate can be controlled within 10%.

To address the problems of low conductivity and poor cycling performance of silicon oxide as negative electrode material, polyacrylamide (PAM) was adopted as a carbon source for the first carbon coating, and the methane-acetylene mixture was used as a gas-phase carbon source for the second coating by chemical vapor deposition to prepare nitrogen-containing double-layer carbon-coated silicon oxide anode materials (SiO_x@ DC-N). Compared with pure gas-phase coated (SiO_x@ GC) and pure liquid-phase coated (SiO_x@ LC) silicon oxide anode material, SiO_x@ DC-N exhibits excellent rate performance and cycling stability, showing that the specific capacity is 850.1 mAh/g at a current density of 4C (1C=1 500 mA/g). The 18650 cylindrical batteries prepared by using a mixed graphite in a ratio of 5∶95 can have a capacity retention rate of 92.70% after 700 cycles of charging and discharging at a current density of 1C.

An interactive orthogonal experiment was carried out. With the metallization rate of the products of fluidized reduction of iron ore powder as dependent variables, reduction temperature, reduction time, gas linear velocity and pressure of reduction as independent variables, the effects of various operating parameters and their interactions on the fluidized reduction of iron ore powder were investigated by means of range analysis and variance analysis. Results show that effects of four factors and their interaction on the metallization rate of fluidized reduction of iron ore powder are in the following descending order: reduction temperature > gas linear velocity > reduction time > pressure of reduction > interaction between reduction temperature and gas linear velocity > interaction between reduction temperature and pressure of reduction > interaction between reduction time and gas linear velocity > interaction between pressure of reduction and gas linear velocity > interaction between reduction temperature and reduction time > interaction between pressure of reduction and reduction time. It is shown that higher reduction temperature is helpful to the combination of iron whiskers, forming a compact structure. A higher gas linear velocity can improve the kinetic conditions of fluidized reduction, which is beneficial to fluidized reduction of iron ore powder.

Fluorite and barite in a low-grade associated ore are intimately intergrown, with the content of 21.2% and 41.7% respectively. Thus, it is hard to separate them via flotation process as they possess similar floatability. In view of the characteristics of this ore, a closed-circuit preferential flotation process consisting of one stage of roughing and seven stages of cleaning was adopted in an experiment, producing a high-quality fluorite concentrate with a yield of 15.60%, CaF₂ grade of 97.36% and recovery of 70.43%, while the BaSO₄ content therein was reduced to only 0.77%. In flotation process, the synergistic effect between inorganic and organic depressants can strengthen the depression of barite and significantly improve the selectivity of fluorite collector, resulting in an efficient separation of fluorite and barite.