A slope of ionic rare earth mine was taken to study the variation of pore water pressure in the slope during and after rainfall events with different rainfall intensity, and the varied critical slip surface during these two periods of time was also studied by using the finite element Morge nstern-Price method. The results show that the rainfall intensity is a significant factor affecting the pore water pressure of shallow slope of ionic rare earth mine. The hysteresis property of rainwater infiltration into the slope is the internal reason for hidden risk of potential slope instability after rainfall events. The greater rainfall intensity will lead to faster formation of the 289 slip surface, higher peak value of greatly changed safety factor, as well as longer influence time. It is proposed for the first time that the development of ionic rare earth mine slope under rainfall conditions may experience four stages: safety, drastic internal variation, high landslide susceptibility, and relative safety.

The influence of hydraulic properties of geogrid on the stability of expansive soil slope was explored by conducting fluid-solid coupling analysis with Plaxis software. On this basis, the principle of flexible support for expansive soil slope under different rainfall conditions was analyzed. It is found that the axial forces on geogrid in each layer of the reinforced slope increase with the continuous infiltration of rainwater, presenting a “convex” shape variation. Without taking consideration of the hydraulic properties of geogrid, the axial forces on the geogrid will be underestimated and the stability of the slope will be overestimated. Flexible support structure can effectively control rainfall infiltration into slope and maintain the shear strength of expansive soil, meanwhile control the slope deformation and displacement growth. Thus, it is regarded as an effective way to support expansive soil slope.

In order to solve the problem of parameter selection for smooth blasting in tunnel/roadway excavation, a parameter selection model based on random forest algorithm was constructed. The input parameters in the model include quality classification BQ of surrounding rock, tunnel (roadway) section area and borehole diameter, and the output parameters include minimum burden, borehole spacing and borehole depth. Then, 24 training samples and 7 test samples were used for training and testing of model, and the results show that the relative errors between the output parameters of borehole spacing, minimum burden, borehole depth and the corresponding parameters of test samples are 17%, 8.8% and 22% respectively on average, indicating that the model is good in selecting minimum burden, but less effective in selecting blasthole spacing and blasthole depth.

To study the effect of sand content on the rheological properties of lacustrine soft soil in northern Hunan, one-dimensional rheological consolidation tests under single-stage load were carried out with soft soil samples prepared with different sand content in the laboratory. The results show that the sand content has a significant effect on consolidation deformation of lacustrine soft soil in northern Hunan. The time of primary consolidation is almost unaffected by consolidation pressure, and decreases linearly with the sand/soil ratio. The higher the sand content in soil, the greater the consolidation pressure, and the smaller the secondary consolidation coefficient. The relationship between the secondary consolidation coefficient and the sand/soil ratio can be well represented by a power function. The higher the content of coarse particles in soft soil, the greater the fractal dimension. There is a linear relationship between the secondary consolidation coefficient and the fractal dimension.

With a flake graphite ore from Africa as the raw material, a beneficiation technique was adopted to recover graphite resource according to ore size fraction. The results show that the fixed carbon content of the graphite feed ore is 32.54%, and the large flake graphite mainly in sheet or banded structure is intergrown with feldspar minerals. The optimized roughing condition is determined as follows: grinding fineness of -0.074 mm 72.87%, kerosene dosage of 50 g/t and terpineol dosage of 150 g/t. A flotation process with one stage of roughing, one stage of scavenging and four stages of cleaning is adopted, in which the large flake graphite is screened from the flotation production of the 1st-stage of cleaning, while the undersize is treated further by three stages of grinding and three stages of cleaning to recover fine flake graphite. The closed-circuit test shows that the fixed carbon content in the large flake graphite (+0.150 mm) concentrate and the fine flake graphite (-0.150 mm) concentrate reaches 96.53% and 96.21%, respectively. The recovery rate of the large flake graphite reaches 22.74%, which is higher by 7.66 percentage points compared to that by conventional regrinding-separation approach.

The effect of hydroxamic acids on flotation of fluorapatite and dolomite was studied. The flotation results show that salicylhydroxamic acid exhibits certain selectivity but low recovery for fluorapatite and dolomite; octylhydroxamic acid shows poor selectivity but high recovery for fluorapatite and dolomite; while benzohydroxamic acid possesses high selectivity and recovery for fluorapatite. The flotation mechanism of fluorapatite and dolomite in the presence of benzohydroxamic acid was studied by performing zeta potential measurement, adsorption capacity test and XPS analysis. It is found that benzohydroxamic acid is an ideal collector for fluorapatite and dolomite.

As for the thickener designed for the new concentrator of a multi-metal mine in Hunan, aiming at the problems of covering a large area, high cost and long period of time for construction, efforts were made to increase the concentration of products from classification for reducing thickener area or even cancelling thickening operation, so as to actualize a simple, efficient and low energy-consuming pre-treatment of feed ore. For this purpose, experiments were carried out to determine parameters, such as hydrocyclone replenishment water, cone angle, cylinder height and apex diameter. It is found that by using a hydrocyclone consisting of a long cylinder and a short cone with cone angle of 90°, cylinder height of 800 mm and apex diameter of 50 mm, the overflow concentration can be increased from 34% to more than 44%, with the classification efficiency up by 0.77 percentage points, and the content of -74 μm size range is stabilized at more than 70%. Therewith, the content of easy-to-separate range increases by 2.19 percentage points and the WO₃ distribution increases by 9.87 percentage points. Furthermore, the grade and recovery of tungsten, molybdenum and bismuth all become stabilized in the follow-up flotation operations.

Experimental study was carried out to realize comprehensive recovery of non-metallic mineral resources from granite tailings in Henan Province, and explore the feasibility of preparing high-purity quartz. The results show that the granite tailings, mainly containing minerals of plagioclase feldspar, quartz, potassium feldspar and mica, have potential to be comprehensively utilized. With a flowsheet consisting sequentially of scrubbing-magnetic separation, pre-treatment of desliming, and mica-feldspar-quartz preferential flotation, a mica concentrate with Al₂O₃, K₂O, Na₂O, SiO₂ and Fe₂O₃ contents of 33.84%, 8.13%, 0.32%, 56.78% and 0.121%, a feldspar concentrate with Al₂O₃, K₂O, Na₂O, SiO₂ and Fe₂O₃ contents of 15.89%, 2.16%, 10.68%, 71.06% and 0.124%, and a quartz concentrate with Al₂O₃, K₂O, Na₂O, SiO₂ and Fe₂O₃ contents of 1.05%, 0.17%, 0.56%, 97.76% and 0.106%, respectively, can be collected. The quartz concentrate can be further purified to obtain a high-purity quartz sand with SiO₂ content of 99.994%.

Based on the properties of Shizhuyuan molybdenum-bismuth sulfide ore, a new eco-friendly collector CYB-06 was developed. The results of industrial experiment show that, when using collectors CYB-06 and ethyl thiocarbamate coordinately, the recovery of molybdenum, bismuth and sulfur in the bulk sulfide concentrate attains respectively to 84.12%, 67.90% and 83.28%, up by 2.32 percentage points, 2.82 percentage points and 6.55 percentage points respectively, and the COD in the wastewater from processing plant is 117 mg/L, declined correspondingly by 41.21%, compared to the concentrate obtained with the combined collector of butyl xanthate and ethyl thiocarbamate. As CYB-06, without pungent odor, exhibits good selectivity index, and leads to low COD in the wastewater from processing plant, its application is of significance for improving product quality and operation efficiency, cleaning production and environmental protection of mining enterprises.

Aiming at the problem of insufficient sorting of low-grade rock ore in the western Inner Mongolia region, the processing technique and equipment were improved to solve the problems including the concentrate of low-grade rock ore with the grade failing to meet the requirement and the grain refinement. By applying automation and intelligent technologies in new equipment, the processing index can be largely improved, which complies with the requirement for the development of green and intelligent mine. Simultaneously, by implementing remote connection, the connection of remote-control center and remote units can be actualized, facilitating the communication between customers and equipment manufacturers, tracking of equipment operation status, as well as the maintenance of operation indicators and observation of component operation status.