In the flotation process of electrode materials from spent LiFePO₄ batteries, the occurrence of entrainment and entrapment usually leads to poor separation effect. Aiming at such problem, selective flocculation with polyvinylpiroxanone (PVP) and polyacrylic acid (PAA) was adopted to enhance the flotation effect in an experimental study, and the interaction mechanism between PVP and PAA and electrode materials was also analyzed. Results show that the firstly added PVP can be selectively adsorbed on the graphite surface by hydrogen bonding, thus inhibiting the spontaneous hydrophobic flocculation of graphite. Then, due to site-blocking effect, the subsequently-added PAA is inhibited to be adsorbed on the graphite surface, leading to selective flocculation of LiFePO₄ by PAA. A combined usage of PVP and PAA can not only make graphite effectively dispersed, but also lead to apparent particle size (D₅₀) of LiFePO₄ cathode material increased from 15.01 μm to 26.17 μm. As a result, the loss of LiFePO₄ due to entrainment in the flotation process of mixed electrode can be effectively reduced, thus the recovery rate of LiFePO₄ cathode material by flotation process can be improved from 71.41% to 83.59%.

Ball milling was adopted to assist leaching of valuable metals from the cathode powder of spent batteries in citric acid and hydrogen peroxide system. It is found that ball milling can exert mechanical energy on the reaction solution, leading to changes in its structure and physical and chemical properties. As a result, chemical reactions can occur, which not only increases reaction rate, but also shortens leaching time. It is shown that after 30 min leaching at 60 ℃, with citric acid concentration of 0.8 mol/L, H₂O₂ at a mass fraction of 20%, liquid-solid ratio of 6∶1, and rotation speed of 60 r/min for a ball mill, the leaching rates of lithium, nickel, cobalt and manganese can reach 99.6%, 99.5%, 99.3% and 98.5% respectively. It is concluded that this processing technique, being characterized by low cost and high efficiency, can provide a certain reference for recycling of spent batteries.

Aiming at obvious elastic-plastic deformation of diamond drill bits in the process of drilling marine gas hydrate, a modeling approach that is suitable for the core drilling process of drill bits was proposed based on the Hertz theory. Firstly, the rock-breaking mechanism was analyzed for marine gas hydrates from elastic deformation to elasticplastic deformation during the drilling process under sea, and the drilling pressure and cutting force of single diamond particle on the diamond bit during the drilling process were calculated. Secondly, according to the stress condition of a single diamond particle, the theoretical relationships between drilling pressure and torque on the whole bit and other drilling parameters were obtained, and a mechanical model was established for the diamond drilling bit. Finally, a relationship curve between the saturation of marine gas hydrate and the torque and drilling pressure was obtained based on analysis. An at-sea testing by adopting such method has successfully taken some samples of marine gas hydrate, which has verified the feasibility of this method. This research provides a theoretical reference for the design of drill bit parameters and optimization of efficient deep-sea core drilling operation.

For discussing rational sequence of drift stoping by cemented backfilling under complex stress conditions, with No.2 mine of Jinchuan Group as an example, a three-dimensional numerical model was constructed with a numerical simulation software, and was then used to analyze the stress field, displacement field and plastic failure zone in drift stoping with different sequences. On this basis, the drift stoping sequence, after optimization by adopting a combined weighting and fuzzy comprehensive evaluation, was then adopted in an on-site industrial experiment. The results show that both mining sequence by overhand or underhand stoping and drift stoping with different spatial sequence can bring a certain influence to the maximum principal stress, maximum tensile stress, vertical displacement, plastic failure zone, as well as the maximum principal stress and vertical displacement in the next stope nearby; mining sequence of underhand stoping followed by overhand stoping, or firstly drift stoping of vertical ore mass, can make the overall mining with higher safety. The on-site experiment with such mining sequence presents better effect. It is concluded that this research can provide some reference in the design and optimization of mining sequence for drift stoping by cemented backfilling under complex stress conditions.

As for the open-pit slope with fault structure, studies on its deformation and failure characteristics were carried out by means of remote sensing images, field investigation and numerical simulation, and its safety factor was also calculated, so as to explore the influence of fault structure on slope stability. Then, based on the analysis of deformation and failure process of slope, the failure rule for open-pit slope with fault structure was discussed. It is found that the landslide hazard occurring on the north slope of the open-pit mine is attributed to an internal factor of fault structure combined with an external factor of unloading by underground mining. Under the combined action of disturbance by underground mining and cutting by F15 fault, a landslide is prone to occur along the fault structure, and then the failure zone will be gradually expanded. The deformation and displacement of upper slope above the F15 fault structure becomes relatively larger, and proceeds towards the eastern bottom along the F15 fault structure. The F15 fault structure changes the deformation and failure trend of the upper part of the northern slope. It is shown that when the safety factor of open-pit slope is 1.45, F15 fault zone is the potential sliding plane, and no larger deformation has occurred along the fault zone of the northern slope.

In order to explore influence of the thickness of barrier pillars reserved in stopes on mining operation during the transition from mining with caving to mining with backfilling in a copper-zinc mine in northwest China, six thickness schemes were selected for the barrier pillars in the stope based on the mining status and the engineering geological conditions. Then, a three-dimensional numerical model was constructed with 3Dmine-Rhinoceros, and factor of safety and zone safety were adopted in the analysis. As for the mind-out area without backfilling in the middle section of upper part, three continuous stope interval mining on the level of 210 m was calculated based on simulation with FLAC^3D, and the changes in roof settlement deformation, factor of safety and zone safety were also analyzed for the barrier pillars left with different thickness after mining. It is found that with the barrier pillars of 12 m in thickness, the stability of stope can be ensured during transition of mining. Thus, it is recommended that the thickness of reserved barrier pillars be no less than 12 m.

Based on the combination of the hunger games search (HGS) algorithm and the artificial neural network (ANN), a new hybrid model of HGS-ANN was developed to predict blasting vibration. Four different prediction models were established based on group method of data handling (GMDH), support vector machines (SVM), ANN and Sadov's empirical formula, and compared with HGS-ANN model in evaluating the performance of models. For this purpose, 32 sets of blasting data of an open-pit mine were collected.7 independent variables, including detonation distance, maximum single-stage charge, total charge, burden, hole spacing, number of holes and hole depth were selected as inputs, while the particle vibration velocity was selected as the output. With the root-mean-square error (RMSE) and the decisive factor (R²) as the evaluating indicators, the established models was compared in terms of their performances. The results show that the HGS-ANN model, with the RMSE and R² of 0.833 and 0.963, respectively, has performance better than the other four models. It is proposed that the HGS-ANN model can be used as an auxiliary tool to optimize the blasting design for reducing the blasting-induced seismic effect.

Based on the engineering geological data and the anchoring support scheme for a foundation pit, a three-dimensional geological generalization model was constructed with ANSYS software for the foundation pit of one bridge over the Yangtze River. This model was then imported into FLAC^3D to simulate and analyze the stress, deformation and plastic zone evolution characteristics of the foundation pit during the process of excavation and anchoring support. The results show that during the excavation of the foundation pit, the rock mass is generally subjected to well-distributed compression, with less concentrated stress. After excavation, the foundation pit generally appears to have an upward rebound deformation, with the displacement of bottom plate maximally reaching 14.7 mm. It is shown that the counter-trend slope on the north side has the maximum deformation up to 8.65 mm. The volume of the plastic zone continues to increase, and then decreases during the excavation of the last step. After the excavation is completed, a large number of plastic zones appear in the rock mass on the north side of the foundation pit. Compared to the support scheme with only anchor rods, the support with anchor rods together with anchor cables can make the deformation of the rock mass of slope on the north side reduced by 16.6% on average, as well as the volume of plastic zone reduced by about 8 600 m³ and the distribution depth reduced from 15 m to 5 m after excavation is completed. It is concluded that the support scheme with both anchor bolts and anchor cables can not only effectively suppress the deformation of the slope on the north side, but also effectively reduce the distribution depth of plastic zone in the rock mass and improve the stability of rock mass, presenting better support effect for the foundation pit slope.

In order to explore the formation mechanism of landslides and reveal the development process of landslides, Mayang Miao Autonomous County in Hunan Province was taken as an example, and landslide analysis was conducted for red beds area in Hunan Province based on susceptibility to the selected factors causing disasters, including elevation, slope, terrain ruggedness index (TRI), stratum lithology and distance away from faults, among others. It is found that landslide occurrence is well correlated with several factors, with susceptibility to each factors in the following descending order: type of land use>elevation > TRI > normalized difference vegetation index (NDVI) > distance away from roads > slope > stratum lithology > distance away from rivers > average rainfall during recent several years > distance away from fault, and the corresponding factors with high sensitivity are listed as follows: land used for buildings, elevation [101 m, 1 394 m), TRI[47 m, 74 m) and NDVI[0.30, 0.43).

A flotation experiment was conducted for a low-grade fine-grained cassiterite from Yunnan. The median dosage of reagent was determined by a single-factor test, and then the reagent dosage for rougher flotation process of cassiterite was optimized by response surface methodology as follows: 285 g/t of activator (KT-51), 13 g/t of inhibitor (OL-1C) and 873 g/t of compound collector (YK-Sn+SN-705). A verification test on flotation with the addition of those agents yielded a tin rougher concentrate grading 1.460% Sn at 74.44% recovery, which was close to the results predicted by response surface methodology. In order to further explore the effect, a closed-circuit test was conducted, resulting in the tin concentrate grading 5.45% Sn at 66.70% recovery. It is shown that efficient recovery of low-grade cassiterite resources can be actualized.