Constitutive models of HJC and RHT for different in-situ stress conditions were established by adopting ANSYS/LS-DYNA software, and the effects of blasting on effective stress and rock damage in different constitutive models were analyzed comparatively. The results show that the effective stress variation in the HJC model is more consistent with practical scenarios, while the rock damage in the RHT model can better reflect practical conditions. In-situ stress has a minor impact on effective stress in regions close to blast holes but a significant influence on effective stress in areas farther away. Additionally, in-situ stress has a smaller effect on rock damage in the HJC model, but substantially affects the damage variables in the RHT model.

Aiming at addressing the difficulty in selecting parameters for the support vector machine (SVM) model in predicting slope safety factors, a Newton-Raphson Backtracking Optimization (NRBO) algorithm was optimized to assist the SVM model in rapidly selecting appropriate hyperparameters. The NRBO algorithm was improved by introducing a dynamic opposition-based learning strategy, horizontal and vertical crossover strategies, and a modified adaptive coefficient calculation formula, so as to construct an INRBO-SVM model for predicting slope safety factors. Six factors, including bulk density, cohesion, internal friction angle, slope angle, slope height and pore water pressure ratio, were selected as model inputs, with the safety factor as the output. The trained INRBO-SVM model, NRBO-SVM model, SVM model and RBF model were used to predict the safety factors of nine test samples. The results show that the INRBO-SVM model exhibits the best performance in safety factor prediction, with a correlation coefficient of 0.999 9, higher than those of the other models. Its root-mean-square error and mean absolute error are significantly lower than those of the other models. Engineering application results indicate that the prediction errors of the INRBO-SVM model for safety factors are all less than 10%, with most below 5%, confirming the accuracy and practical application value of the model in predicting safety factors.

In order to assess stability of the current multi-level mined-out areas in Qijiaojing iron mine in Subei County Bolun Mining Development Co., Ltd.of Western Mining Limited Company, the mine excavation process was simulated with FLAC^3D software to mainly analyze the stress and displacement changes in the mined-out areas after multi-level excavation. The results indicate that the stress in the mined-out areas is predominantly compressive stress, which is primarily concentrated in the roof and pillars of the stope. The maximum compressive stress, approximately 20 MPa, is observed in the pillars of the mined-out area at the 2 150 m level. It is found that the mind-out area has the maximum settlement of 20.30 mm and the maximum horizontal displacement of 7.22 mm, being satisfactorily stable. However, long-term exposure of large-scale mined-out areas may lead to deformation and collapse of pillars. Therefore, regular inspections and reinforcement measures should be taken for the pillars during subsequent production processes.

The south slope of the Jingxi-Barak mining area of Xinjiang Jinchuan Mining Industry was taken for study. As for the issues of weakening mechanical parameters of slopes after an earthquake and the stability assessment of slopes under aftershocks, a BP neural network model optimized by the crow search algorithm (CSA-BP) was proposed for the inversion of mechanical parameters of slopes after an earthquake. The stability of slopes with dangerous rock mass under aftershocks was evaluated by using the discrete element method. The results show that the CSA-BP model can quantitatively reveal the weakening characteristics of rock masses through the inversion of mechanical parameters. Under aftershock of a magnitude 5 earthquake, significant displacement occurs in the tuffaceous sandstone in the middle and upper parts of the slope, with horizontal (x-direction) displacement far exceeding vertical (z-direction) displacement, indicating that slope instability is dominated by horizontal sliding. The CSA-BP model can accurately identify high-risk zones through a parameter-dynamic coupling mechanism, providing theoretical support for slope protection after earthquakes.

Ultra-fine iron ore tailings were modified through thermal activation, and then together with some waste rock were taken for mixed calcination. With the mass ratio of iron ore tailings to waste rock, calcination temperature and calcination time as variables, and the compressive strength of specimens and the content of chemically bound water as the objectives for optimization, an orthogonal experiment was carried out to analyze the sensitivity and influence trends of each factor on the target values, and the hydration products of the cemented materials were also analyzed. The results indicate that with an increase in the mass of waste rock, the specimen compressive strength initially increases and then decreases. As the calcination temperature rises, the specimen compressive strength monotonically decreases. As calcination time is prolonged, the specimen compressive strength first decreases and then increases. In consideration of both calcination cost and material performance, an optimal calcination scheme is finally determined, including iron ore tailings and waste rock in a mass ratio of 7∶3, a calcination temperature of 800 ℃, and a calcination time of 2 h. Under these conditions, the 3-day, 7-day and 28-day compressive strengths of the specimens can reach 4.18, 6.36 and 9.87 MPa, respectively. The main hydration products of the cemented materials are calcium silicate hydrate gel, rankinite, ettringite and hydrotalcite.

The western No.2 mining area of a certain mine adopts the non-pillar sublevel caving in mining, and excessive wedge cut height in the 1 546 m sublevel leads to poor blasting effect. To address this problem, blasting with wedge cut was specially studied. Firstly, the rock parameters were calibrated based on the RHT constitutive model and the damage threshold of the rock was determined to be 0.4 by a fluid-structure interaction analysis with the LS-DYNA software. A comparative analysis of the cut blasting effects with different cut width shows that with the cut height fixed at 23 m, the effective damage rate of the rock presents a unimodal distribution with an increase in cut width. The optimal cut width is found to be 24 m, with which the effective damage rate of the rock can reach a peak value of 0.692 5. Based on these parameters, the on-site application of designed cutting scheme indicates that over 85% of blast-forming space can meet the requirement, presenting a reasonable fragment distribution of muck pile, with the angle of repose at approximately 40°.

As for a mine in Yunnan, the failure modes of surrounding rock in roadways buried at a depth of 1 500 m was analyzed by adopting a combination of theoretical analysis, in-situ monitoring and numerical simulation for exploring the variation law of surrounding rock stress. The results indicate that the surrounding rock in the main transportation roadway and the drift transportation roadway near the ore body at a depth of 1500 m predominantly belongs to Class Ⅰ and Class Ⅱ rock masses. The influence of stratum stability on the broken zone is greater than that of the roadway cross-sectional dimensions. Under the disturbances of surrounding rock stress, mining-induced stress and blasting loads, the stress in the arch corner of the roadway is higher than that in the side walls. Based on the failure modes of the surrounding rock, a support method combining rock bolts, steel mesh and shotcrete was proposed. The 3DEC numerical simulation results show that after support, the depths of the plastic zones in the side walls, roof and floor of the roadway are reduced by 0.5 m, 0.8 m and 0.6 m, respectively.

In a Hunan polymetallic ore concentrator, the tailings with CaF₂ grade of 26.56% exhibit certain economic value. However, due to the influence of residue reagents in the upstream processing of main tungsten-molybdenum-bismuth minerals and the interference of calcium-bearing gangue, it is extremely difficult to recover fluorite from the tailings. A process consisting of selective regrinding, tailings discarding by high intensity magnetic separation, and fluorite flotation was adopted with a new reagent NH-1 as activator of fluorite, CY-63 as collector of fluorite, SWG+SZY as depressant of silicate and micro-fine gangue, and CYAB as depressant of calcareous gangue. As a result, fluorite concentrate with CaF₂ grade of 90.50%, CaCO₃ content of only 1.35% and CaF₂ recovery of 79.50% was finally reclaimed in the closed-circuit test. It is concluded that such tailings resources can be comprehensively utilized by adopting this process.

As for a gold-bearing pyrite from Hebei Province, the influence of four oxidants, including H₂SO₄, H₂O₂, HNO₃ and KMnO₄, on its floatability was investigated, and the adsorption of collectors on pyrite was also explored by infrared (IR) analysis and electrochemistry measurement. The flotation test shows that with H₂SO₄, H₂O₂ and HNO₃ as oxidants, moderate oxidation can promote the floatability of pyrite, while the oxidation of KMnO₄ can obviously depress the floatability of pyrite. The IR analysis shows that the effects of these four oxidants on pyrite-collector interaction are in the following descending order: HNO₃>KMnO₄>H₂O₂>H₂SO₄. The oxidation of KMnO₄ may passivate pyrite and reduce its floatability. Electrochemical analysis shows that H₂SO₄ and HNO₃ have obvious oxidation effects on pyrite. By increasing oxidant concentration, the double xanthate formed on pyrite due to its reaction with xanthate will be oxidized by H₂O₂ solution, and the hydrophobic layer on pyrite will be destroyed, leading to the decline of pyrite's floatability.

The parameters of lifter bars in the design of a Φ12.2 m×6.7 m semi-autogenous grinding (SAG) mill liner for the Las Bambas concentrator in Peru were optimized by employing discrete element method, and a quadratic regression model was constructed based on response surface analysis to investigate the effect of various factors on total collision energy and energy dispersion. The results indicate that lifter height has a significant impact on particle motion behavior, and it can alter drop height, particle trajectory and moving range, thereby impacting the collision energy during grinding process. The face angle and width of lifter can influence the distribution of collision energy by adjusting particle positions in the cascading and grinding zones. Based on a comprehensive consideration, the optimal lifter parameters are finally determined as follows: height of 380 mm, width of 100 mm, and face angle of 30°.