A 5 mm thick DL510 ultra-high strength steel (1 500 MPa) was welded by using metal active gas (MAG) arc welding. The influence of heat input on the microstructure and mechanical properties of weld joint was investigated, and the residual weld stress of the joint was eliminated by hammering while welding. The results show that with heat input within the range of 43-70 kJ/cm, the obtained weld joints can have a good shape. If hammering time is less than 20 min, the tensile strength of weld joint increases as hammering time prolongs; however, after hammering time exceeds 20 min, there is little variation in the tensile strength. With the increasing of heat input, the grain size of weld joints grows obviously, and a small amount of fine granular bainite structure appears in the coarse-grained area with the heat input of 70 kJ/cm, leading to improvement in the toughness of weld joints.

With laser high-energy beam as heat source to initiate exothermic reaction, Cu-Al powder was compacted and sintered into Cu-Al alloy containing in-situ formed hard reinforcing phase Al₂O₃ by laser-induced self-propagating synthesis. The effect of Cu-Al ratio in the composition on the microstructure and properties of alloy system was explored. The results show that the microstructure of Cu-Al alloy is a multiphase structure composed of hard reinforcing phase Al₂O₃ and matrix of CuAl₂, AlCu₄, Al₄Cu₉ and other intermetallic compounds. The alloy has rich dendritic crystals in microstructure, and becomes more uniform and fine-grained with the increase of aluminum content. Increasing the content of aluminum to a certain range is helpful to improve the compactness of sintered products. With copper and aluminum in a mass ratio of 33.2∶66.8, the sintered product has the lowest porosity (10.57% ), the highest microhardness (373HV) and the best wear resistance (with wear rate of 0.137 g/mm²).

An orthogonal experiment was performed for laser welding of 5 mm ZL114A and 6061 aluminum alloys, and the influences of welding parameters on the microstructure and mechanical properties of welded joint were investigated. It is shown that the influences of three parameters of laser welding power, defocus and welding speed are in a descending order. With laser welding power of 3 kW, welding speed of 16 mm/s and the defocus of -3 mm, the welded joint has an average tensile strength of 208.03 MPa and the elongation of 5.16%. Compared to ZL114A and 6061 aluminum alloy, the tensile strength is reduced to 64.14% and 65.60%, respectively, while the elongation is reduced to 41.38% and 33.70%, respectively. The welded joint presents a mixed mode of brittle and ductile fracture when failing under tensile.

Based on the theory of metal oxidation and the mechanism of diffusion rate control, a kinetic model was established for high temperature oxidation of Cr-Fe alloy plate. The effects of composition, temperature, atmosphere, partial pressure of oxygen on the oxidation behavior of the alloy were studied. The results show that the established oxidation kinetic model can quantitatively present an oxidation process of Cr-Fe alloy plate, by which the calculated results are in good agreement with the experimental results. The oxidation characteristic time (t_Φ) of the Cr-Fe alloy is about (3-4) × 10^-14 s, and t_Φ in argon atmosphere decreases gradually with the increase of Fe content in the alloy. Partial pressure oxygen doesn' t bring significant impact to the oxidation rate of alloy, and all products from the equilibrium oxidation of alloy in argon atmosphere are Cr₂O₃. According to the standard of oxidation resistance of superalloy, Cr-Fe alloy in air atmosphere can meet the rating standards for oxidation resistance and secondary oxidation resistance.

ZnO narowires were synthesized by adopting hydrothermal synthesis, and ZnO/activated carbon composite material was then prepared by compounding activated carbon powder and nano-ZnO. The research on the sensing performance of such composite to ethanol gas shows that the sensor with ZnO/activated carbon composite presents good response and recovery characteristics to ethanol gas at 150 ℃. Its sensitivity to the ethanol with concentration of 5 × 10^-6 can be up to 4.75, and will increase positively with the increase of ethanol concentration, which presents a reproducibility and stability.

An experiment on non-quenched and tempered steel F45MnVS was carried out by adopting controlled cooling after hot rolling. The mechanical properties, decarburized layer and microstructure of rolled steel without cooling and after controlled cooling process were compared for analysis. The results show that controlled cooling after hot rolling can lead to the steel with yield strength, elongation, section shrinkage and impact energy improved all, and with the decarburized layer being effectively controlled or even "disappeared". With the surface temperature of the hot-rolled steel decreased to 650 ℃, granular bainite begins to occur on the steel surface; with the surface temperature down to 460 ℃, much granular bainite occurs on the steel surface. It is shown that by using controlled cooling after hot rolling, the ferrite and pearlite on the steel surface and near 1/2 radius on the cross section of the steel become fine-grained. The total ferrite net is reduced, and long strip ferrite is transformed to blocky ferrite. Due to larger size, the central part of steel shows little difference in the microstructure.

A self-designed multi-functional rod was adopted to provide a real-time monitoring of surrounding rock stability during the excavation of a metal mine, and the variations of vertical stress of rock stratum and surrounding rock vibration occurrence within the monitoring range of the multi-functional rod during stoping were all recorded. It is found that the stress and peak ground velocity of the surrounding rock are all trending up as excavation area increases, which reflects that more fractures occur inside the surrounding rock, leading to lower degree of stability for the surrounding rock, and the excavation damage zone (EDZ) goes deeper. As for mines supported by top threaded anchor bolts, the EDZ evolution process and caving of rock mass can be more effectively controlled when the thread length of rod is greater than the depth of EDZ. After one month's mining of this stope, it is found that the vertical stress of the rock stratum within the monitoring length of the multifunctional rod increases by 3.9 MPa due to the subsidence of the stratum, and the frequency of vibration occurrence meets the blast vibration standard for safety permit in China. It is shown that the surrounding rock has a good stability based on the comprehensive evaluation.

A database including 336 sets of engineering practical samples was established for rockburst prediction based on literature research. An improved salp swarm algorithm (ISSA) was adopted to optimize the support vector machine (SVM), and then an ISSA-SVM model was constructed for predicting the rockburst intensity grade and its effectiveness was also verified. Results show that this ISSA-SVA model for rockburst prediction can have accuracy up to 94.0%, much higher than other model, which can provide a certain scientific basis for rockburst prevention and control.

The upper middle section in the West 2^#Mining Area of Jinchuan Longshou Mine, with the mining method changed from underhand cut-and-fill mining to sublevel caving without sill pillar, was taken as an example for studying extraction of the orebody in a confined space from sublevels of stope. A combined scheme was prepared with different ore-drawing method for each sublevel. As for the first and second sublevels, the total amount of mined ore in the ore drawing is controlled to ensure the safe caving of roof and forming of overburden. And ore drawing by controlling ore dilution is adopted for the third sublevel for avoiding ineffective dilution, so as to achieve high-quality ore recovery. For the fourth sublevel, a scheme of ore drawing by controlling ore dilution in the normal stope drift plus ore-drawing by controlling cutoff grade in an auxiliary extraction drift is designed to achieve a full and effective ore recovery. Experiments were then performed with three groups of different ore-drawing schemes, and results show that a combined ore-drawing scheme can achieve safe and effective mining of orebody in a confined space, but also has a significant advantage in controlling loss and dilution of ores, which can bring the mine good economic benefit from mining. It is concluded that this research can provide scientific theory and technical guidance for the following engineering practice.

For determining support parameters in an advancement project of the secondary shaft of Comica Mining's Kamoya copper-cobalt mine in the DRC, 25 sets of testing schemes were designed by using Box-Behnken based on the engineering geological conditions. After numerical analysis with FLAC^3D, the mechanical response characteristics under various support conditions were obtained. In combination with technical and economic requirement, analysis hierarchy process and principal component analysis were adopted for the combined weighting of nine selected indices, including advancement cost, maximum tensile stress among others, and then a comprehensive evaluating model was established for the parameters of shaft support. A multivariate second-order regression prediction equation was then obtained with the comprehensive scores as response indicators, and shaft support parameters as the variables. It is found that shaft is supported with 35 anchor bolts with thread length of 2.5 m arranged in horizontal direction, with spacing of 1 m in vertical direction, as well as the concrete lining with strength grade of C35, and the best comprehensive benefits can be obtained.