Influence of coal particle size on gas adsorption equilibrium time

The degree of coal pulverization leads to the difference of gas adsorption state in coal, which has an important impact on the gas migration time in coal pores. The research results play an important role in improving the accuracy of gas content determination in coal. In this paper, coal samples from Machang Mine were chosen as the research object to observe the relationship between particle size and the equilibrium time, the adsorption isotherms and the adsorption equilibrium time of coal with four degrees of particle sizes are measured in the laboratory. The conclusions are as follows: the smaller the degree of particle sizes is, the larger the gas adsorption capacity of coal sample is. The isotherms can be divided into four parts: “micron, ten microns and small particle size hundred microns, large particle size hundred microns and millimeter”. With the increase of particle size degree, coal sample adsorption equilibrium time is rapidly increasing, in which, the adsorption equilibrium time for the coal sample with the minimum particle size was only 5 min, but for the largest particle size was more than dozens of days, which means that the impact of diffusion path will increase rapidly with the increase of degree of particle sizes. Comprehensive analysis shows that the adsorption equilibrium time of coal sample with 100 μm particle size can be significantly shortened and the gas content determination accuracy can be improved

Landslide Accumulation Ice-Snow Melting for Thermo-Hydromechanical Coupling and Numerical Simulation

In this paper, we discussed the phase change coupling algorithm of accumulation bank slope under the action of ice-snow melting. We described the effect of temperature gradient on the water migration of soil. We simplified the stress balance, continuity, and energy equation in the coupled model. We discussed the variation law of temperature, seepage, and stress (deformation) field under different conditions of ice-snow melting on the bank slope of the accumulation body. Based on the three-field coupling energy balance equation of ice-snow melting with phase change, the simplified algorithm of three-field coupling is obtained. The simplified algorithm is applied to the coupling model of ice-snow thawing on indoor accumulation bank slope. We established a practical numerical model for the coupling analysis of temperature, seepage, and stress field. We established the coupled control differential equation of three fields. We investigated the three-dimensional numerical simulation of stress, displacement, plastic deformation, and other indicators. The results show that the numerical simulation results are in good agreement with the monitoring results. It is expected that the research results can more truly simulate the actual characteristics of ice and snow melting water on the bank slope of the Three Gorges Reservoir and provide reference for the prevention and prediction of extreme snow and ice disasters in the Three Gorges Reservoir area

Mechanical Properties of Sandstones under Initial Unloading Damage

To study the influence of initial unloading damage on the mechanical properties of sandstone, the repeated loading test of unloading damaged sandstone was carried out considering 8 initial unloading quantities of 100%, 93.33%, 86.67%, 80%, 73.33%, 66.67%, 40%, and 0%. The results were compared with those of the triaxial compression test of intact samples. The results show that the peak strength of intact samples is higher than that of unloading damaged samples, and the difference is more obvious when the unloading quantity is more than 80%. During the unloading process, the strain increasing rate of rock samples is obvious, and the lateral dilatation is significant, and the deformation modulus and compressive strength of the rock sample deteriorate obviously. From the energy point of view, the greater the unloading damage, the smaller the stored elastic strain energy, which leads to the decrease of peak strength. At present, the unloading fracture inside the rock sample has developed, and the failure mode of the sample gradually changes from compression shear failure to tensile shear failure. In the process of engineering rock mass excavation, the unloading area and unloading damage amount of the rock mass is a dynamic adjustment process. To ensure the safety of the engineering rock mass, it is suggested to determine reasonable reinforcement time, reinforcement area, and reinforcement measures

Pressure Relief Mechanism and Gas Extraction Method during the Mining of the Steep and Extra-Thick Coal Seam: A Case Study in the Yaojie No. 3 Coal Mine

Gas disasters, such as coal and gas outburst and gas overflow, always occur during the mining of the steep and extra-thick coal seam in the horizontal, fully mechanized, top coal slice caving (HFMTCSC) method. To solve these issues and guarantee the safe and efficient mining in the Yaojie No. 3 coal mine, 3DEC software was used in this work to investigate the overburden movement and collapse law as well as the stress redistribution and coal-seam deformation characteristics below the goaf. The results show that a pressure arch structure and a hinge structure are formed in succession in the overburden rock, which induces stress redistribution in the coal below the goaf. During the mining of the upper slice, more than 75% of the coal in the lower slice is located at the effective pressure relief zone; therefore, the steep and extra-thick coal seam can then be protected slice by slice. Meanwhile, with the increase of mining depth, the efficient pressure relief range expands. Based on this pressure relief mechanism, crossing boreholes and bedding boreholes were reasonably designed to efficiently extract the pressure relief gas during the mining of the steep and extra-thick coal seam in the Yaojie No. 3 coal mine

Pressure Relief Mechanism and Gas Extraction Method during the Mining of the Steep and Extra-Thick Coal Seam: A Case Study in the Yaojie No. 3 Coal Mine

Gas disasters, such as coal and gas outburst and gas overflow, always occur during the mining of the steep and extra-thick coal seam in the horizontal, fully mechanized, top coal slice caving (HFMTCSC) method. To solve these issues and guarantee the safe and efficient mining in the Yaojie No. 3 coal mine, 3DEC software was used in this work to investigate the overburden movement and collapse law as well as the stress redistribution and coal-seam deformation characteristics below the goaf. The results show that a pressure arch structure and a hinge structure are formed in succession in the overburden rock, which induces stress redistribution in the coal below the goaf. During the mining of the upper slice, more than 75% of the coal in the lower slice is located at the effective pressure relief zone; therefore, the steep and extra-thick coal seam can then be protected slice by slice. Meanwhile, with the increase of mining depth, the efficient pressure relief range expands. Based on this pressure relief mechanism, crossing boreholes and bedding boreholes were reasonably designed to efficiently extract the pressure relief gas during the mining of the steep and extra-thick coal seam in the Yaojie No. 3 coal mine

Study on the mechanical properties of unloading damaged sandstone under cyclic loading and unloading

Abstract To reveal the mechanical properties of rocks under stress disturbance and unloading confining pressure, conventional triaxial compression tests, triaxial compression tests on unloading damaged sandstone, and cyclic loading and unloading tests on unloading damaged sandstone were conducted. Then, the evolutionary characteristics of dissipated energy in sandstone under cyclic loading and unloading were explored, and damage variables were proposed. The crack development characteristics were analyzed from a microscopic perspective. The study results reveal that: (1) the sandstone exhibits obvious brittle failure under different stress paths, and the macroscopic failure mode is dominated by shear failure. As the number of cycles increases, the load-bearing capacity, elastic modulus, and deformation modulus of the sandstone will be significantly reduced if it suffers greater unloading damage. (2) The cyclic action in the early stage inhibits the development of the internal fracture. However, the inhibitory effect is significantly reduced for specimens with larger unloading quantities. The damage variable in the cyclic loading and unloading is about 50.00% of that in the unloading, indicating that unloading confining pressure is the dominant factor for specimen failure. (3) The extension of microcracks within the sandstone is dominated by intergranular cracks, and the number of cracks increases with the increase of unloading quantity. After cyclic loading and unloading, the structure becomes looser. The test results deepen the understanding of rock mechanical behavior and fracture evolution under cyclic loading and can provide a basis for structural stability improvement under stress disturbance and unloading confining pressure

Reservoir Landslide Physical Modelling under Ice-Snow Melting and Reservoir Water Combined Action

Extreme ice-snow melting in winter affects the infiltration process of snow water on the slope surface significantly and plays an important role in the deformation stability of landslide. Variation in pore water pressure is regarded as an essential factor of landslide instability induced by snow water. In order to figure out the internal relationship between the infiltration process of snow water and the failure mode of deformation and instability of the accumulation landslide, the response law and deformation and failure mode of pore water pressure and soil pressure of landslide accumulation under different ice-snow melting conditions are deeply studied based on the indoor large-scale landslide model test. We have studied the physical model test under the combined action of reservoir water and ice-snow melting. It reveals the seepage erosion deformation and failure mechanism. It undoubtedly provides references of great importance for the geological hazard governance of bank slope in the Three Gorges Reservoir Area

Lactate Efflux Inhibition by Syrosingopine/LOD Co‐Loaded Nanozyme for Synergetic Self‐Replenishing Catalytic Cancer Therapy and Immune Microenvironment Remodeling

Abstract An effective systemic mechanism regulates tumor development and progression; thus, a rational design in a one‐stone‐two‐birds strategy is meant for cancer treatment. Herein, a hollow Fe3O4 catalytic nanozyme carrier co‐loading lactate oxidase (LOD) and a clinically‐used hypotensor syrosingopine (Syr) are developed and delivered for synergetic cancer treatment by augmented self‐replenishing nanocatalytic reaction, integrated starvation therapy, and reactivating anti‐tumor immune microenvironment. The synergetic bio‐effects of this nanoplatform stemmed from the effective inhibition of lactate efflux through blocking the monocarboxylate transporters MCT1/MCT4 functions by the loaded Syr as a trigger. Sustainable production of hydrogen peroxide by catalyzation of the increasingly residual intracellular lactic acid by the co‐delivered LOD and intracellular acidification enabled the augmented self‐replenishing nanocatalytic reaction. Large amounts of produced reactive oxygen species (ROS) damaged mitochondria to inhibit oxidative phosphorylation as the substituted energy supply upon the hampered glycolysis pathway of tumor cells. Meanwhile, remodeling anti‐tumor immune microenvironment is implemented by pH gradient reversal, promoting the release of proinflammatory cytokines, restored effector T and NK cells, increased M1‐polarize tumor‐associated macrophages, and restriction of regulatory T cells. Thus, the biocompatible nanozyme platform achieved the synergy of chemodynamic/immuno/starvation therapies. This proof‐of‐concept study represents a promising candidate nanoplatform for synergetic cancer treatment