With a water cut-off and slope reinforcement project in Tenglong open-pit mine in Hebei Province as the background, a three-dimensional numerical model was established for finite slope with a retaining wall. Firstly, this numerical model was verified for its validity, and then was adopted in numerical simulation and analysis for the distribution law of earth pressure on the back of wall under translational motion. The results show that as the bench becomes wider, the angle of inclination for sliding surface of finite slope falls down to zero first, and then is gradually increased. When the bench is 9 m wide, the numerical solution of passive earth pressure on the back of wall is almost consistent with the analytical solution in term of its variation rule, which fully verifies the validity of this numerical model. The passive earth pressure presents nonlinear distribution, and the active earth pressure presents convex curve distribution. With both the stability of retaining wall and the construction cost taken into consideration, it is recommended that the slope degree should be set at 30° and the bench should be 9 m wide.

An all-weather moving target detection method by using Retinex algorithm based on HSV color space conversion was proposed for complex situation in a mine, which changed the detection of moving target to the detection of special marker on the moving target, and extracted the original grey image of the target by color space conversion. The histogram of grey distribution was used to judge whether to restore the low-illumination image. And special markers were selected in the scene, and the original image was converted to HSV color space. Then, the corresponding ROI region was selected, and the binary image was obtained based on the threshold value. After smoothing of the data, the Canny operator was used to extract contour information, thus characteristic parameters of the marker was extracted. The practice proves that the characteristic parameters of the markers can be accurately obtained by this method, which can thus solve the problem of connector falling off from mechanical equipment under complex situation. It is shown that this method is of certain practical significance in engineering application.

A new directional core acoustic emission technique was used to measure in-situ stress of the gas storage reservoir construction area of the Zhangbei Comprehensive Energy Project in Hebei Province. Results show that three boreholes buried at depth of 90 m have the corresponding in-situ stress dominated by horizontal structural stress, with the maximum principal stress approximately in the same north-south direction. In addition, the circumferential wave velocity anisotropy analysis method was conducted for verification, and the results show that the maximum principal stress is in a direction consistent with the result obtained from the acoustic emission testing of borehole core, which further verifies the correctness of the measurement by acoustic emission technique for the borehole cores.

Random Forest (RF) and eXtreme Gradient Boosting model (XGboost) were adopted to assess the landslide hazard in Changsha City, and frequency ratio (FR) was then used to check and verify the obtained result. A vulnerability assessment system was established based on analytic hierarchy process (AHP) and then adopted to make vulnerability assessment. Finally, efficient risk assessment was realized by integrating the results of hazard assessment and vulnerability assessment with numerical classification method. It is found that RF model is similar to XGBoost model in its evaluation performance, but XGBoost model regulated by FR method can bring a more accurate assessment. Also, the vulnerability assessment has the largest weight value of population density, and high vulnerability areas are mostly concentrated in downtown area and traffic arteries. The areas with relatively higher and high risk account for about 4.6% of the entire study area in Changsha City, which are mainly concentrated in valleys, towns and traffic arteries.

In order to obtain the information of landslide in forest area, a high-resolution digital terrain model was derived from LiDAR point cloud, and the data of landslide in forest area were extracted by Res-Unet network and persistent homology. The Fenghe Experimental Forest in Washington State of USA was selected for study, among which three areas were selected for quantitative analysis. Based on calculation, the extracted data of landslide in the forest area show an average precision of 79.7%, an average recall rate of 70.2%, and average F₁ of 65.5%. The extraction method based on Res-Unet and persistent homology can accurately identify most landslides in the research area. It is shown that by using deep learning and persistent homology, this extraction method can make up for the weakness of traditional remote sensing methods in extracting landslide information in vegetation covered areas, and also provide a technical support for landslide analysis.

In order to explore the reliability of type selection in the design of lift pipe for underwater transport system in deep sea mining, hydrodynamic parameters were checked with transport indices as input for design. Based on the settling velocity of polymetallic nodules, anti-fatigue threaded sleeve of P110 steel, with outer diameter of 244.48 mm and wall thickness of 20.24 mm, was selected for lift pipe. And a towing test performed in a pool shows that the resistance drag coefficient is 1.4 for the lift pipe at the upper end of the pump and 1.3 at the lower end of the pump. Hydrodynamic parameters were calculated and analyzed for the underwater transport system according to working conditions and launching conditions, showing that the safety factor of lift pipe can meet the requirements of API RP 2RD Standard. In the deep-sea polymetallic nodules mining test project, lift pipe in the at-sea acceptance test, with reliable joint connection, could meet the requirement for each transporting parameter, which has verified that the type selection of lift pipe in the design is acceptable.

Calculation was made for four typical pipelines by adopting typical critical flow rate and frictional pressure drop calculation model. The precision of the model was analyzed by comparing the calculated value with the measured value of four pipelines. The results show that as for flow rate and pipe diameter, the calculated values from Wasp model, HAN Wenliang model, FEI Xiangjun model and LIU Dezhong model are in good agreement with the measured value, presenting the maximum deviation within the range of ± 15%. FEI Junxiang model presents higher precision in the calculation of frictional pressure drop, with the maximum deviation within the range of ± 10%, but also has certain margin in calculation. It is concluded that FEI Xiangjun model can provide an important basis and reference for the design of long-distance transportation.

Experimental studies were carried out for iron recovery from the leaching residue of lateritic nickel ore containing 51.38% TFe and 2.01% S, by adopting processing techniques of centrifugal separation, magnetic separation and magnetic roasting. It is found that the process of magnetic roasting followed by magnetic separation is an efficient technique to recover iron from such leaching slag. It is shown that the process of coal-based reduction followed by low-intensity magnetic separation (LIMS) can produce the concentrate grading 62.77% TFe at 94.04% recovery, and the process of gas-based reduction followed by LIMS leads to the concentrate grading 68.77% TFe at 95.15% recovery, with sulfur content of 0.12% in the impurity, which can meet the quality standard for iron concentrate. Although the process of direct reduction followed by LIMS can produce the concentrate grading 90.89% TFe at 88.90% recovery, it is shown that there is higher content of sulfur in the concentrate.

In an experiment for Cu/Mo separation of a copper-molybdenum bulk concentrate, ozone oxidation technique was applied to enhance floatability difference between chalcopyrite and molybdenite. Under adequate ozone oxidation conditions, a molybdenum concentrate grading 47.46% Mo at 94.96% recovery, with Cu content of 0.10% can be obtained from a closed-circuit flotation test adopting a flowsheet consisting of one stage of roughing and three stages of cleaning. It is shown that the flotation indicators obtained by applying ozone oxidation technique is superior to that by using Na₂S as the depressant, which indicates that the ozone oxidation technique can be used to substitute Na₂S depression approach for Mo flotation whilst depressing Cu.

After iron tailings was subjected to preconcentration followed by magnetizing roasting process, the obtained product was taken in an experiment to be processed respectively by adopting a grinding and magnetic separation process and a combined process of grinding plus magnetic separation followed by flotation process. The roasted ore with TFe grade of 33.19% was processed using a grinding and magnetic separation approach, resulting in an iron concentrate grading 63.04% TFe at 80.04% recovery at a grinding fineness of -0.025 mm 97%. Although the processing flowsheet is simple, it is still hard to achieve such a grinding fineness in commercial practice and the grinding cost is also extremely high. However, a process consisting of grinding, magnetic separation and flotation, with a grinding fineness of -0.025 mm 85%, can produce an iron concentrate grading 65.36% TFe at 73.39% recovery. Therewith, such grinding fineness is commercially practicable and the grinding cost can be obviously reduced.