The effect of Cr content on microstructure and heat exposure of Al-Cu-Mg-Ag alloys was investigated. It is found that strength of the alloys at room temperature decreases after an initial increase as Cr content increases, and the 0.2%Cr alloy exhibits excellent room-temperature mechanical properties. Transmission quantitative calculation results suggest that an addition of 0.2%Cr can promote precipitation of Ω phase and improve coarsening resistance of Ω phase in the alloy after heat exposure. With the addition of Cr exceeding 0.3%, the (Al, Cr, Mn, Ti)-enriched phases precipitate at the grain boundaries of the alloy, leading to coarser grains.

The phase structure, microstructure and mechanical properties of Fe_46-xNi₂₀Co₂₀Cr₁₀V₄Al_x (x=5, 8, 12, 15) high-entropy alloys with different Al contents (atom fraction, %) were systematically investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and performing uniaxial tensile test. The results show that with the increase of Al content, the phase structure of Fe_46-xNi₂₀Co₂₀Cr₁₀V₄Al_x high-entropy alloys transforms from single-phase structure of face-centered cubic (FCC) to dual-phase structure of FCC and body-centered cubic (BCC). Also, the strength increases and ductility decreases. The Fe₃₄Ni₂₀Co₂₀Cr₁₀V₄Al₁₂ high-entropy alloy annealed at 900 ℃ exhibits an excellent strength-ductility balance, with yield strength, tensile strength and elongation to failure at 593 MPa, 1009 MPa and 32.13%, respectively. With Al content of 5%, the as-cast and annealed high-entropy alloys remain single FCC phase. However, with Al content of 8%, 12% and 15%, the high-entropy alloys all become FCC-BCC phase. The annealing treatment promotes the precipitation of BCC phase, and the proportion of BCC phase increases with increasing annealing temperature.

When ultra-high strength steel with tensile strength more than 1 600 MPa and BS700 high-strength steel with tensile strength more than 760 MPa are joined together by metal active gas welding, weld cracks are prone to occur in the seam of joint. To solve this problem, comparative welding tests were performed by using ER70-G or ER307Mo welding wire with diameter of 1.0 mm, respectively, with initial welding current of 160-180 A, voltage of 21-24 V, and final welding current of 190-210 A, voltage of 23-26 V. The comparison of process and weldability show that welding with ER307Mo can lead to the sample with bending property obviously better than that by welding with ER70-G. The sample after welding with ER70-G can be found to have micro-cracks not going through the whole cross section of welding seam, with cracking rate on the cross section of seam reaching 35.29%, but no cracks are found on the section of welding seam by using ER307Mo. It is concluded that the ER307Mo welding wire is more suitable for welding ultra-high strength steel and BS700 high strength steel. The study has solved the cracking problem in the joint of ultra-high strength steel and BS700 high strength steel, which can provide a solution for the welding of dissimilar high-strength steel with larger difference in tensile strength.

Theoretical calculation was made for the flow field in the hydraulic transportation with deep-sea polymetallic nodule collector, and the relationship between particle size of polymetallic nodules and minimum conveying speed was obtained. The distribution of flow pattern in the conveying channel was simulated with the jet velocity of nozzle at 15 m/s, 20 m/s and 25 m/s respectively, and rate of the flow at 30 mm away from the lower surface of the channel was measured. A laboratory test was conducted for nodules pick-up by using a collector with different jet velocities of nozzles, and it is found that the obtained results are consistent with the theoretical calculation and simulation results.

Based on the in-depth investigation of the geological characteristics of the phosphate mines in western Hubei, including Sujiapo Phosphate Mine, Maping Phosphate Mine and Taoyuxi Phosphate Mine, rock burst phenomena were analyzed in terms of influencing factors of occurrence position, buried depth and lithology. The appropriate control measures are proposed for rock burst in those phosphate mines in western Hubei. In-situ stress of underground phosphate rock in western Hubei was tested. Based on the obtained results, the mining sequence was optimized to avoid mining operation in the stress concentration area as much as possible, and pressure relief and support measures were taken in local areas to ensure safe underground mining.

In order to simply and effectively evaluate slope stability, four machine learning models based on chaotic particle swarm optimization (CPSO) were proposed to solve the existing problems of algorithm selection and hyper-parameter optimization in traditional machine learning model, and their prediction performance were comprehensively compared among each other. A database consisting of 221 open-pit slope stability cases was established, in which 80% of the data were used for training and 20% for model testing. Based on the comparison between the prediction results of four models and the verification results of engineering practices, it is found that the support vector machine (SVM) based on CPSO is superior than other three machine learning models in terms of prediction of slope stability, presenting an accuracy up to 88%. Thus, it can provide a reliable prediction for the safety of slope in open-pit mine.

The lifting of polymetallic nodules was simulated by using a CFD-DEM coupling approach, and the influence of different swirling flow on hydraulic lifting of polymetallic nodules in vertical pipelines was explored. The results show that as swirl ratio increases, the intensity of swirl will be enhanced significantly, and both the maximum fluid velocity and the average axial velocity of particle group will increase. It is found that intensity of swirl can bring obvious impact to the distribution of particles with different velocity in the pipe, showing that particles with high velocity are gradually distributed around the pipe wall, while the particles with low velocity in the center of the pipe. Swirling flow can reduce the local concentration of particles, which is beneficial to reducing the risk of pipeline blockage due to higher concentration of particles caused by retention effect.

Based on the analysis of ore dilution in Barun mine, the dilution rate at the junction of ore and rock in Barun open-pit mine was controlled. With the actual production into consideration, some controlling measures are put forward for the mine, including accurately identifying ore-rock boundary by drilling and sampling, separating ore and rock by blasting, accurately identifying the ore-rock boundary in muck-pile by blasting, and optimizing shovel loading operation among others. As a result, less waste rock has been mixed with ore, leading to the ore dilution down to below 2%. It is shown that the rate of extraction can be obviously improved.

The key factors of pile foundation settlement were explored for the slope under vertical load by using grey relational analysis, and it is found that each factor is in the following descending order by its influence: elastic modulus > slope distance > slope gradient > internal friction angle > cohesion > soil density > poisson's ratio of soil > pile length > pile diameter. In order to optimize the parameters of support vector regression (SVR) model, a novel HGWO-SVR model was proposed by integrating the differential evolution-enhanced gray wolf algorithm (HGWO). Compared with GWO-SVR and GS-SVR models, this model presents obvious advantage in prediction, with high accuracy and minor error. A settlement prediction model for pile foundation of slope was constructed based on HGWO-SVR model, and the prediction results were compared with those values calculated with existing settlement formulas. The results show that the maximum percentage error between the prediction value of HGWO-SVR model and the calculated value is 6.55%, thus verifying that this model is feasible in settlement prediction for pile foundation of slope.

The ground surface displacement caused by open-pit mining of a large iron mine in Hainan was analyzed by using fuzzy measurement theory. Base on the comparison with the calculated results by using the theory of random media, it has verified that the fuzzy measurement theory is superior and practicable in the analysis of influence of open-pit mining on the surrounding environment.