Monitoring and early warning of dynamic roof hazards in mines is crucial for mining production and personnel safety. Traditional multi-point displacement monitoring and early warning methods rely on a single absolute threshold based on monitoring data, resulting in poor sensitivity and reliability of the warning. In response to this issue, a new early warning method for dynamic roof hazards in mines was proposed based on multi-point displacement data and the Autoregressive Integrated Moving Average (ARIMA) model. In this method, superposition techniques were employed to enhance the signal-to-noise ratio of multi-point displacement time series data, and a graded early warning method combining enhanced windowed waveform characteristic function ratio and kurtosis was introduced, which addressed the inadequacies of traditional threshold warnings. Furthermore, a dynamic weighted parameter ARIMA model was constructed to predict displacement data, enabling the integration of monitoring and prediction data for early warning of dynamic roof hazards in mines. The theoretical testing of this method shows a false alarm rate of 13.3%, with an average error of 15.4% for secondary or higher warning characteristic values. The test results of engineering actual data of kurtosis over two periods show that the warning false alarm rates are 11.8% and 6.7%, respectively, and the average errors of the secondary or higher warning characteristic values are 15.1% and 14.4%, respectively. In summary, the proposed early warning method for dynamic roof hazards in mine has a high application value.

In order to reveal the dynamic variation law of seepage field and stability of the dump slope under long duration rainfall, a case study of the dump in the Democratic Republic of the Congo was conducted. Based on the saturated-unsaturated soil mechanics theory, Geo-Studio software was used to simulate the seepage field of groundwater and perform the limit equilibrium analysis of the dump slope after long duration rainfall. The results show that the rainfall is mainly vertical infiltration in the initial stage, and it is mainly lateral infiltration in the later stage. The initial water level rises rapidly, and gradually decreases after 2 d of rainfall, and tends to be stable after 25 d. Under the condition of short duration rainfall, the safety factor of slope fluctuates whereas under prolonged rainfall, it initially decreases and then increases, and the minimum safety factor appears about 4 d after rainfall. The impact of rainfall on the stability of dump slope has a certain degree of persistence and hysteresis, and safety prevention and control measures should be taken for the slope with poor initial stability.

In order to study the dynamic response characteristics of adjacent roadway under blasting action, taking the adjacent roadway of a mine as the engineering background, the 3DEC discrete element simulation software was used to establish a bonded block model considering the discontinuous characteristics of rock mass. The vibration velocity field, stress wave propagation and fracture evolution law of surrounding rock of adjacent roadway under blasting load were simulated, and the response characteristics of the surrounding rock under different blasting rising time was analyzed. The results show that the short rising time makes the energy of blasting wave release intensively, which leads to the high peak vibration velocity of surrounding rock particles, but the attenuation is rapid. The long rising time makes the energy distribution more uniform, but the peak vibration velocity of surrounding rock particles decreases significantly, and the cumulative damage to surrounding rock is more significant. The evolution of fracture fractal dimension presents two-stage characteristics, which increases sharply in the early stage of blasting and increases slowly in the later stage. The long rising time has a stronger promoting effect on the expansion of surrounding rock damage range. Based on the stress wave propagation and the distribution law of the peak particle velocity of the surrounding rock, the short rising time is suitable for efficient blasting scenarios, while the long rising time needs to be combined with charge control to reduce the damage of the surrounding rock. The research results provide a theoretical basis for the safety design and construction control of blasting excavation in adjacent roadways.

In order to solve the problem of foundation cracking and deformation of the ore transportation conveyor belt system in S2—S3 section, which are located in the southern open-pit of the MS Mine of Serbia Zijin Copper Doo, a survey on the current status of foundation cracks, geological investigation, and monitoring of foundation deformation was conducted. It is found that poor rock properties are the main cause of cracking and deformation in the belt corridor foundation. The self-load and operation vibration of the belt corridor, mining blasting vibration, rainfall and snowfall are also important factors that induce foundation cracking and deformation. To ensure the stability of the belt corridor foundation, a treatment scheme was proposed to reinforce the foundation using double-row micro-piles and frame structures. The monitoring results indicate that before taking reinforcement measures, the belt corridor foundation of the S2—S3 section is continuously declining, and the west slope adjacent to the belt corridor shows a trend of sliding. After implementing reinforcement measures, good reinforcement effects is achieved, and the cracking and deformation trend of the belt corridor foundation is suppressed, effectively controlling the development and expansion of cracks, improving the overall integrity and bearing capacity of the foundation, and effectively controlling the propagation and transmission of cracks. The research results can provide a reference for similar geotechnical engineering reinforcement and treatment.

The prediction of mine pit inflow and the spatio-temporal variation of groundwater seepage fields in underground mines is of great significance for mine water control engineering, which is directly related to mine safety production and environmental protection. A copper-cobalt mine in the Democratic Republic of Congo (DRC) is located in a small nappe within the Zambia-DRC metallogenic belt, featuring complex hydrogeological conditions. If the traditional drainage scheme is adopted, the predicted mine pit inflow will exceed 46 000 m³/d. Through on-site hydrogeological condition investigation, a single-layer control drainage scheme was proposed by utilizing the vertical multi-layer structure of the mining area's aquifer and the principle of control drainage. By applying the theory of groundwater flow and numerical simulation techniques, a three-dimensional groundwater numerical model was established to accurately reflect the hydrogeological characteristics of the mining area. Combined with the optimization of drainage borehole layout scheme based on water gushing points during underground development, the prediction shows that the mine pit inflow during the mining period of the 940 m level can be reduced to 25 260 m³/d. The mine has been constructed according to the optimized control drainage scheme, achieving pressure-controlled mining in the first mining section. Compared with the traditional drainage scheme, it saves approximately 2.34 million US dollars in drainage costs annually. The single-layer control drainage method can provide a reference for similar high-water mines in Africa, thereby achieving the reduction of mine pit inflow, protection of mining area water resources, and efficient pressure-controlled mining.

In order to study the effect of heat treatment on the physical and mechanical properties and strength change mechanism of clay-rich sandstone, the clay-rich sandstone specimens were heat treated at 25 ℃, 200 ℃, 400 ℃, 600 ℃ and 800 ℃, respectively, and the physical parameter measurement test and uniaxial compression test were carried out on the specimens after heat treatment.The results show that with the increase of heat treatment temperature, the mass of sandstone specimens decreases continuously, the wave velocity and elastic modulus increase first and then decrease, the porosity and peak strain decrease first and then increase. The strength of the sandstone specimens shows strengthening characteristics at 25 -600 ℃ heat treatment temperature, and shows deterioration characteristics at 600 - 800 ℃ heat treatment temperature. Finally, the strength change mechanism of clay-rich sandstone is revealed from three aspects: particle thermal expansion, mineral dehydration, mineral phase change and thermal decomposition. The research results provide a reference for the study of the thermal characteristics of clay-rich sandstone, and lay a theoretical foundation for the repair and reinforcement of underground space rock engineering under high temperature.

Weak interlayer is usually the main internal factor of rock slope instability, and rainfall is the main external factor of slope instability. For rock slope with weak interlayer, it is of great significance to study its instability mechanism and seepage characteristics to prevent slope instability. Taking the limestone open-pit slope with multiple weak interlayers in Nanshan, Chibi, Hubei Province as the research object, the instability characteristics of the slope were deeply explored by numerical simulation method, and the unsaturated seepage characteristics of the slope were studied based on the unsaturated seepage theory. Finally, the Morgenstern-price method was used to calculate the safety factor of each potential slip surface under the influence of seepage field. The results show that the weak interlayer is the main reason for the instability and failure of the slope, whether it is the overall instability and failure of the slope along the weak interlayer or the local instability and failure of the step. Under the influence of rainfall, the change of pore water pressure in the slope gradually develops from the surface to the depth, but the influence depth is limited. For the feature points with a certain distance from the slope surface, the increase of pore water pressure and volumetric water content has a “lag” phenomenon. The safety factor of each potential slip surface of the slope decreases, which decreases greatly in the early stage of rainfall, and tends to be stable in the later stage of rainfall.

Both rock slope instability and tunnel collapse disasters in cold regions are related to the frozen seepage flow in rock fractures. In order to explore the evolution mechanism of the frozen seepage flow in rock fractures at low temperature, a visualized experiment platform for frozen seepage flow in rock fractures under low temperature conditions was developed, and experiments of low temperature frozen seepage flow in rock fractures under different flow conditions were carried out. Based on the image-processing technology, the dynamic development process of liquid-ice phase transition was quantified, then the relationships between the liquid-ice phase transition and the frozen seepage flow properties were analyzed. The results show that due to the difference in heat exchange intensity between liquid phase and fracture surfaces, the liquid phase is frozen firstly in the upper and lower regions of fracture outlet in the frozen seepage flow process. With the development of frozen seepage flow, the areas of ice phase increase gradually, and the seepage channel decreases accordingly, which results in the increase of liquid phase velocity and an intensification of thermal convection intensity under constant flow conditions, so that the ablation phenomenon occurs at the convex places of the ice phase on both sides of the fracture. When the frozen seepage flow reaches a steady state, the Reynolds number of liquid phase flow is obviously greater than its initial value, and the pressure gradient is roughly linear with the flow. Furthermore, the larger flow has an obvious inhibitory effect on the freezing rate of the ice phase.

Chambishi Copper Mine is a typical high-water-inrush mine in Africa, and the hydrogeochemical study of its pit water inrush is crucial for groundwater prevention and control engineering. A total of 2 groups of surface river water samples and 16 groups of pit water inrush samples were collected. Using a combination of Piper trilinear diagrams, ionic ratio coefficients, and Phreeqc modeling, the hydrochemical characteristics and main controlling factors were analyzed, the water inrush sources of the main and western ore bodies were revealed, as well as the hydrochemical evolution mechanism. The results show that the hydrochemical type of pit water inrush is mainly SO₄−Ca⋅Mg type, and the hydrochemical composition is mainly controlled by the dissolution of gypsum and dolomite, with a small amount derived from the dissolution of feldspar. The chert dolomite aquifer, serving as the main water filling source, is continuously distributed within the regional scope. Within the mining area, groundwater flows from the western ore body area to the main ore body area. Affected by the caving mining method in the main ore body area, the chert dolomite aquifer directly recharges the ore body aquifer. The quartzite aquiclude is unevenly distributed, with thinning or absence in some sections. Under natural conditions, there is a hydraulic connection between the chert dolomite aquifer and the ore body aquifer. Combining the current situation of the mining area and the hydrochemical characteristics of water inrush, the prevention and control strategy of “blocking as the main approach and drainage as the auxiliary” has been proposed, providing a basis for underground water prevention and safety production.

The influence of graphene oxide (GO) on the properties of sulfoaluminate cement-based grouting materials was investigated. The macroscopic performance tests reveal that with the increase of GO dosage, the fluidity of the slurry decreases, but the mechanical properties of sulfoaluminate cement-based grouting materials are significantly improved. When the GO dosage is 0.01%, 0.03%, 0.05% and 0.07%, compared with the control group, the 7-day compressive strengths are increased by 4.7%, 14.1%, 13.3% and 11.7% respectively. The mechanical strength enhancement effect of the material is the most significant when the GO dosage is 0.03%, indicating that GO has a remarkable promoting effect on the hydration reaction of sulfoaluminate cement-based grouting materials, and 0.03% is the optimal dosage. XRD and SEM analyses reveal that GO optimizes the microstructure through a bridging effect. Although no new products are formed, the stability of sulfoaluminate cement-based grouting materials and their durability in underground environments are significantly enhanced. The study indicates that GO can improve the early strength and long-term durability of sulfoaluminate cement-based materials, which is of great value for engineering applications.