The methane adsorption at room temperature in the interlayer of the kaolinite–methanol complex (Kln–Me) with different methanol content is investigated with grand canonical Monte Carlo (GCMC) simulation. The mechanism and structure of methanol intercalated kaolinite (Kln) is proposed, and the effect of methanol on methane adsorption by Kln–Me is discussed. The results indicate that the methanol adsorption in the Kln interlayer is mostly physical with non-bonded energy. The interlayer spacing ( d) of Kln–Me optimized by the DREIDING force field is in good agreement with the experimental data measured with X-ray diffraction. The configuration, adsorption properties, and adsorption isotherms are obtained for eight Kln–Me systems with different number (2–20) of methanol molecules in interlayer space. By comparing methane adsorption in the Kln–Me interlayer with different number of methanol molecules, we discover the complex interplay of factors influencing methane adsorption in the Kln–Me interlayer, especially the number of methanol molecules and free volume. It is found that the adsorption capacity of Kln can be enhanced by inserting methanol molecules into its interlayer. This analysis also underscores the GCMC simulation as a viable tool to calculate kaolinite/organic intercalation composites for potential applications.
Abstract Based on the S1201-2 large height mining in the 2–2 coal seam of Ningtiaota colliery with on-site microseismic measurement, physical simulation and theoretical analysis methods, this paper explores the rule of roof movement in thick coal seams with roof cutting and non-pillar (hereinafter referred to as RCN-P) mining, so as to obtain scientific and effective theoretical basis for entry support and to summarize the regional structural characteristics and dynamic periodic fracture characteristics. As can be seen from microseismic events, the entry roof is featured by "two zones and one line" along the horizontal direction, namely, the crack generation area, the roof movement area. Additionally, and the obvious lateral breaking of the entry roof on the coal wall is a typical feature of the thick coal seam with RCN-P mining. The roof is vertically divided into "three zones", the crack generation area, the roof movement area and the crack development area. The roof cutting activity mainly affects the overburden activity within the basic roof height range, which is also the roof movement area. In addition, the distribution frequency and the intensity of microseismic events indicate the roof periodic breaking characteristics. The "breaking pressure relief,” “advanced crack development,” and “the limit breaking state” of roof breaking corresponds to the initial, middle, and final stage of breaking in the periodic weighting process, respectively. Compared with the normal mining, the RCN-P mining reduces the periodic weighting length and increases the pressure strength. As is shown in the physical simulation experiment, the basic roof and the cutting control layer in the "regional structural characteristics" constitute the “large” and “small” structures with RCN-P mining. The basic roof key layer is the core to control the stability of the strata, and the breaking process from the cantilever beam to the short masonry beam of the roof-cutting control layer is the main cause of the entry stress. Correspondingly, the basic structure model of “short masonry-hinged” roof was proposed and the calculation method of support was established for the entry with RCN-P mining in thick coal seam, providing a research foundation for scientific and effective rock formation control.
The uniaxial compression creep test is used to study the cemented coal gangue backfill body specimens with different cement-sand ratios (1:4,1:6,1:8, respectively). Through the processing and analysis of the creep curve, we discussed the influence of different cement-sand ratios, stress load and loading time on the strain, creep rate and long-term strength of the backfill body. These studies have revealed the creep law of the backfill body and obtained accurate conclusions. The results show that: (1) Different proportions of cemented coal gangue backfill body under the action of the set step by step axial loading stress, the strain is positively correlated with the change of loading stress. (2) With the increase of axial stress, the instantaneous deformation of cemented coal gangue backfill with three kinds of cement–sand ratio increases with the decrease of cement–sand ratio under the same axial stress. (3) With the increase of the axial stress of the three kinds of cement–sand ratio cemented coal gangue backfill body, the strain rate of the deceleration creep speed and the constant creep stage increases, and the duration of the deceleration creep stage increases. The average creep strain rate of the three kinds of cement–sand ratio cemented coal gangue backfill materials before entering the accelerated creep stage is determined. (4) Using an improved steady-state creep rate inflection point method, the long-term strength of three kinds of cement–sand ratio of cemented coal gangue backfill is determined, and it is concluded that the long-term strength decreases with the decrease of cement–sand ratio, which is positively correlated.
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