The main cause of underground disasters in coal mines is the stress concentration and high-intensity unloading of surrounding rock caused by man-made mining and the extraction of coal resources. Especially when the surrounding rock is affected by confined water, it is easy to lose stability and damage, which leads to the occurrence of disasters. Accordingly, the experimental study on the mechanical properties and energy evolution law of sandstone under the coupling of seepage and mining stress was carried out by means of Rock Top multi-field coupling tester. The test results show that: (1) The total stress-strain curve of sandstone can be divided into five stages. After the sandstone begins to unload, it changes from axial deformation to circumferential deformation. (2) The peak stress of sandstone increases with the increase of unloading level. With the increase of osmotic pressure difference, the peak stress of sandstone is not obvious due to the superposition of surrounding rock and water pressure. (3) The higher the unloading level of sandstone is, the larger the axial strain value at the peak stress is, and the axial deformation of sandstone is more obvious under high unloading level. The evolution law of dilatancy angle curve of sandstone roughly follows the law of ' increase—ecrease—increase—decrease ', and the expansion behavior of sandstone is more significant under low unloading level. (4) With the increase of initial unloading level, the elastic strain energy density of sandstone increases as a whole. The energy distribution coefficient of elastic strain energy density increases first and then decreases with the increase of axial strain of rock sample. (5) The instantaneous energy distribution coefficient of elastic strain energy of sandstone presents the change rule of 'increase—decrease—increase 'with the increase of axial strain of rock sample. The energy storage capacity of sandstone elastic strain energy reaches its peak after entering the elastic deformation stage, and its energy release capacity reaches its peak before entering the residual stress stage. © 2025 Biodiversity Research Center Academia Sinica. All rights reserved.

The effect of oxidation degree of graphene oxides (GO) on their removal from wastewater via froth flotation was studied in this work. Four types of GO samples with different oxidation degrees were synthesized and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), atomic force spectroscopy (AFM) et al. The effects of cetyl trimethyl ammonium bromide (CTAB) concentration, pH, stirring time on the removal of GO by froth flotation had been discussed. It was found that the addition of CTAB could improve surface hydrophobicity of GO, endowing GO to be easily separated by froth flotation. The removal was dependent on CTAB dosage, pH and stirring time. Moreover, the removal first increased and then decreased with the increasing oxidation degree of GO, and less kinetic energy input was needed to overcome the energy barrier between GO flocs with the increase of oxidation degree. The removal mechanism was proven to be electrostatic attraction, and the different contents of oxgenous-containing functional groups in GOs with various oxidation degrees played a vital role in their removal via froth flotation. (C) 2020 Elsevier Ltd. All rights reserved.

Due to the challenges of separation and high costs, coal slime is often directly burned without further separation processing, leading to environmental pollution. Therefore, a feed -regulated water -only cyclone has been proposed to improve the coal slime separation efficiency by controlling the suspended bed. This method optimizes particle characteristics by incorporating a pre-desliming hydrocyclone, the characteristics of particles were optimized to regulate the hindered settling in suspension layer. Response surface experiments were conducted to investigate the impact of structural parameters on separation efficiency, Additionally, under optimal parameter conditions, particle size and density were characterized, and a simulation analysis was conducted using CFD-EDEM. The results showed that the maximum separation efficiency achieved in the experiment was 35.31%. Particle characterization analysis also revealed that, after feed regulation, the proportion of particles with a size of 0.045 mm within high density exceeded 75%. Industrial application experiments demonstrated the feasibility of obtaining a high -quality coal product with over screen yield of 9.29% and an ash content of 9.47%. This transformation of coal slurry into a valuable resource has generated significant economic benefits for enterprises and will address the environmental pollution issue caused by direct combustion and improper disposal.

Rock mass disasters are caused by instability driven by energy within the rock mass. The excavation and unloading disturbance can lead to fractures and instability in the rock mass structure, which is a major cause of dynamic disasters such as water inrush in stopes. To understand the influence of excavation unloading on rock mass structure fractures and to clarify the degradation law of surrounding rock and the mechanism of dynamic disasters like water inrush, this study focuses on the characteristics of rock damage and the evolution of energy under stress-seepage coupling factors. Using the Rock Top multi-field coupling tester, the study investigates the rock damage characteristics and energy evolution under three stress paths: conventional triaxial compression (group C), conventional unloading confining pressure with different initial damage degrees (group W), and cyclic loading and unloading confining pressure (group X) under the influence of stress-seepage coupling. Based on the evolution characteristics of rock elastic strain energy, the stress-strain curve of rock under conventional triaxial compression (group C) is divided into five stages, and the characteristics of U1, U3, Ue, Ud and permeability change in each stage are explained in detail (Ue is the elastic strain energy, Ud is the dissipated energy, U1 is the strain energy of the rock transformed by the positive work done by the axial stress on the rock, and U3 is the strain energy released by the negative work). During the conventional confining pressure unloading process, the evolution law of U1 and U3 is similar to that of group C rock, but the negative growth of U3 is more significant. The rock input energy gradually shifts from Ue to Ud, and the initial damage degree has no significant influence on the law. During the confining pressure unloading process, the permeability shows a fluctuating upward trend, and the confining pressure is negatively correlated with the permeability. In the process of cyclic loading and unloading confining pressure, the energy evolution law is similar to that of group W rock, with energy accumulation differing only due to time effects. On the whole, regardless of the stress path, the pre-peak rock is dominated by Ue, representing energy storage, while post-peak rock is dominated by energy release and dissipation. Axial stress loading is the main influencing factor for rapid accumulation of Ue, while the change in confining pressure is not enough to cause a large change in Ue. Axial load is the primary factor influencing engineering disasters. Furthermore, there is a significant negative correlation between rock damage variable and confining pressure. The larger the confining pressure is, the smaller the Ue release ratio of rock is, and the smaller the rock damage is. Confining pressure restraint effectively enhances the energy storage capacity of rock and inhibits the dissipation and release of rock energy. © 2024 Biodiversity Research Center Academia Sinica. All rights reserved.

In order to explore the law of deterioration and damage of roadway surrounding rocks and to clarify the water inrush mechanism of roadway spalling，laboratory tests on deterioration and seepage characteristics of sandstone under three stress paths of conventional triaxial(group C), conventional discharge of confining pressure(group W) under different initial damage degrees，and cyclic loading and unloading confining pressure discharge(group X) were carried out based on Rock Top multi-field coupling tester. The results show that：(1) At the beginning of cyclic loading and unloading confining pressure of group X rocks，the axial deformation of rocks is slower than the lateral and volume deformation，but cyclic loading and unloading confining pressure can lead to "strain accumulation" of rock，which makes the stress drop point of rock in group X appears "hysteresis effect" compared with group W. (2) The initial damage significantly affects the rock strength and the sensitivity to the confining pressure. The initial damage degree of rocks in group X and group W is negatively correlated with the unified confining pressure drop parameter(η )，and positively correlated with the incremental ratio of the strain and the confining pressure(λi ). The parameter η of group X is smaller than that of the group W，while λi is greater than that of the group W. (3) Obvious brittle failure of rocks occurs in groups X，group W and group C，and the main failure mode is shear failure. When the initial damage degree is low，the rock failure degree of group X is large，accompanied by local macroscopic cracks. (4) The rock permeability is affected by the factors such as rock pores，framework structure and crack development. The rock seepage-strain relationship curves of groups X and group W can be divided into three stages. The first and third stages are consistent. In the second stage，the rock permeability of group X decreases first and then increases，while the rock permeability of group W increases as a whole. (5) The permeability fluctuation of group X tends to be obvious with the increase of the circulation grade. The higher the initial damage degree is，the more easily this phenomenon occurs. The number of cycles has little effect on this law，but the increase of the number of cycles has an inhibition effect on rock seepage，and the inhibition effect is more significant than that caused by the decrease of confining pressure. © 2023 Academia Sinica. All rights reserved.

In order to explore the mining failure law of deep coal seam floor and clarify the mechanical behavior and energy change in the floor strata during mining, the mechanical properties and energy evolution law of sandstone under cyclic loading with different confining pressures (20, 30, 40 MPa) were studied using the Rock Top multi-field coupling tester. The results are as follows: (1) the hysteresis phenomenon of a rock stress-strain curve under cyclic loading is evident. Moreover, the hysteresis loop migrates to the direction of strain increase, and the fatigue damage caused by cyclic loading has a certain weakening effect on the peak strength of rock; (2) both the number of cycles and the axial strain show a nonlinear change characteristic that satisfies the quadratic function relationship. Among them, the stress level of the rock is the main factor affecting the fitting effect; (3) under the same confining pressure, with an increase in cycle level, the macroscopic deformation of the rock increases, the accumulation of fatigue damage in the sample increases, and the irreversible deformation of the rock increases, which leads to an increase in energy input and dissipation; (4) in terms of elastic energy and dissipation energy, elastic energy plays a dominant role. In the initial cycle, the rock is destroyed, and the rock energy loss is great. After the second cycle, the input energy is mainly stored in the rock in the form of elastic energy, and only a small part of the input energy is released in the form of dissipation energy; (5) the confining pressure can improve the efficiency of rock absorption and energy storage, enhance the energy storage limit of rock, and limit the dissipation and release of partial energy of rock. The greater the confining pressure, the more evident the limiting effect, and the more significant the dominant position of elastic energy; and (6) the change in the energy dissipation ratio can be divided into three stages: rapid decline stage, stable development stage and rapid rise stage. The greater the increase in dissipation energy, the greater the degree of rock damage. The evolution process of the energy dissipation ratio can reflect the internal damage accumulation process of rock well, which can be used as the criterion of rock instability.

The energy applied during breakage is the key to enhancing the magnetite liberation degree and improving quality. The relationship between energy and liberation properties remains unclear due to various complicated factors affecting mineral liberation. Therefore, this work aims to study the effect of energy on the breakage characteristics of magnetite ores; the impact breakage test was conducted on magnetite particle groups at different energies using a drop weight impact tester; the statistical analysis was performed based on the fractal theory to research the particle size distribution; the fracture morphology and liberation properties of these ores were analyzed using scanning electron microscope and mineral liberation analyzer. Results show that the particle size distribution of magnetite after breakage conforms to the fractal law. The larger the energy, the greater the fractal dimension for this distribution, showing a linear relation between them, which implies that the fractal dimension can evaluate the breakage degree. The fracture morphology of magnetite ores indicates that as the energy increases, the intergranular fracture evolves into transgranular fracture, proving the influence of energy on fracture modes. It is found that the magnetite liberation degree first increases and then decreases with the rising of energy, indicating that the magnetite liberation can be improved at an appropriate amount of energy. The above conclusions provide a theoretical reference for optimizing energy and improving broken product quality.

In order to explore the lagging water inrush mechanism of deep coal seam floor and to clarify the seepage and mechanical characteristics of floor strata during mining，the Rock Top multi-field coupling tester was used to carry out stress-seepage coupling experiment of sandstone under different confining pressures(20，30，40 MPa) and cyclic loading. The results show that：(1) The complete stress-strain curve of rock under cyclic loading can be divided into five stages，including primary micro-fracture compression closure stage，elastic compression stage，crack stable development stage，crack rapid development stage and post-peak deformation failure stage；(2) Under different confining pressures，the peak strength of rock under cyclic loading decreases slightly compared with that under conventional triaxial compression，but the stress-strain curve shows obvious hysteresis；(3) With the increase of the number of cyclic loads，the dissipation energy periodically decreases，and the elastic modulus gradually decreases with the increase of the axial stress difference during the first cycle；(4) Under the same hydrostatic pressure，the permeability of sandstone after failure increases significantly compared with that before failure，and with the increase of the unloading level，the permeability increment is consistent with the growth rate；(5) Under different confining pressures and cyclic loads，the pre-peak permeability changes periodically with the increase of the stress difference，and the post-peak permeability decreases obviously with the decrease of the stress difference；(6) Under different confining pressures and cyclic loads，sandstone mainly shows shear failure，and with the increase of the unloading level，the degree of damage increases. Under 20 MPa confining pressure，sandstone shows a single shear failure. Under the cyclic load of 30 MPa and 40 MPa confining pressure，there is a crack network dominated by through shear cracks and supplemented by secondary tension cracks. © 2022 Academia Sinica. All rights reserved.

To solve the problem of the unsatisfactory effect of grouting reinforcement in broken rock mass, a cement-based composite slurry was successfully prepared by using ordinary Portland cement as the main material in this study. By conducting a single factor test, orthogonal test, and organic compound modification test, the effects of different addition ratios of fly ash, clay and waterborne polyurethane, epoxy resin, and other organic materials on the grouting performance of cement slurry were analyzed. In addition, a grouting simulation test system was used to verify the reinforcement effect of the prepared composite slurry. The results indicate that the addition ratio of clay and fly ash has a strong influence on the strength and stone rate of cement slurry. The final setting time of the best mixed slurry can be shortened to 11 h, and the compressive strength after 28 days can reach 18 MPa. The composite slurry modified by organic materials has a reinforcement coefficient of up to 4.6 for crushed sandstone, which significantly improved the brittle failure phenomenon of the reinforcement stone body and, thus, has high application value.

In this study, Montmorillonite nanosheet/poly(acrylamide-co-acrylic acid)/sodium alginate hydrogel beads with high handle capacity towards dyes effluent was investigated. Montmorillonite nanosheet cooperated with acrylamide and acrylic acid via hydrogen bond, amidation and polymerization interaction first, then crosslinked with sodium alginate by intertwining interaction to form 3D network structure, achieving free entrance and rapid adsorption for dye molecules. Batch adsorption tests revealed a multilayer and heterogeneous adsorption of methylene blue (MB) onto hydrogel beads according to pseudo two-order kinetic model and Freundlich isotherm model. The adsorption capacity of MB was controlled by the amount of adsorption sites in hydrogel beads, which could reach maximum of 530.7 mg/g. The adsorption mechanism is attributed to Ca ion-exchange and chemical bonding of -COOH and -OH groups with MB. Column tests showed an excellent dynamic adsorption performance of hydrogel beads towards MB wastewater compared with the traditional commercial adsorbents of granular active carbon and cation exchange resin, which achieved 380 bed volume (BV) of treated sewage to meet the emission standards using the single column. Moreover, 1625 BV and more treated dye effluent was achieved to be safety discharged via double column series in 5 circulation-regeneration, indicating the great potential of hydrogel beads in practical application. Such hydrogel realized the performance promotion of macromolecule polymers and nanoclay in materials design, and green application in water treatment.