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The deformation and failure characteristics of roadways in stratified rock masses are heavily influenced by the dip angle of the rock layers. Therefore, it is crucial to select an appropriate cross‐sectional shape and support scheme to ensure roadway stability. This study utilizes a discrete element numerical simulation method to systematically investigate the failure modes of roadways in stratified rock masses under varying dip angles. The theory of pressure balance arches is integrated to establish optimal principles for determining the cross‐sectional shape, and corresponding support schemes are proposed for roadways in stratified rock masses. The results indicate that as the dip angle of the rock layers changes, different failure modes occur, ranging from symmetric arch‐shaped collapse to asymmetric wedge‐shaped collapse and overall sliding failure. Based on the self‐stabilizing properties of roadways under pressure balance arches, a straight‐sidewalls and arch‐roof cross‐section is recommended for roadways with arch‐shaped or overall sliding failures in their roofs, and a pentagonal cross‐section is recommended for roadways with wedge‐shaped collapses. The support parameters determined by well‐established empirical criteria are generally applicable to roadways with arch‐shaped or wedge‐shaped roof failures. However, caution should be exercised when applying these parameters to roadways with overall sliding instabilities, as they may result in insufficient design robustness. Finally, a field case study of a copper mine in Zambia is presented to demonstrate the process of recommending appropriate roadway cross‐sectional shape and support scheme. [ABSTRACT FROM AUTHOR]

To investigate the effective utilization of agricultural and forestry wastes for mitigating the shortage of primary energy and environmental pollution, the pyrolysis behavior of corn straw (CS), wheat straw (WS), and poplar sawdust (PS) was studied using thermogravimetric–Fourier transform infrared (TG‐FTIR) analysis. The activation energies and pyrolysis mechanism functions of different biomass types were calculated. The results showed that the functional group structures of the gaseous products generated from the pyrolysis of different biomass types were similar, mainly including OH, aliphatic CH, CO, aromatic ring skeleton, aromatic CH, and CO groups. These functional group structures mainly existed in oxygen‐containing compounds such as phenols, ketones, aldehydes, acids, esters, alcohols, and ethers. The pyrolysis process of agricultural and forestry wastes exhibited certain differences, with the PS undergoing thermal decomposition more easily, while the thermal decomposition mechanism functions of the two agricultural wastes (CS and WS) were similar. PS had a later initial release time for volatile matter, and the oxygen compounds produced by its pyrolysis were the highest, followed by WS and CS. [ABSTRACT FROM AUTHOR]

The filling treatment of complex large goaf is limited by the filling capacity of the mine, and the treatment site always shows the situation of "filling and caving". Large caving speed will lead to the goaf to burst through the surface, which is extremely unfavorable to the safety management of the goaf and the safety production of the mine. Taking the complex caving goaf of an iron mine in Tangshan as the engineering background, the 3D laser scanning technology is used to detect the goaf morphology, and the expansion trend of goaf is analyzed by comparing the previous three detection results. Combined with discrete element software 3DEC, a complex numerical calculation model is established to simulate the caving process of goaf surrounding rock under filling conditions, master the space-time evolution characteristics of goaf filling and surrounding rock caving, and put forward the filling treatment scheme of goaf section. The results show that the goaf boundary expands both vertically and horizontally at the initial stage of the formation of the caving area, and the key to the governance of this space-time area is to timely support the caving arch foundation to limit the increase of the span of the goaf. When the filling reaches the -210 m level, the horizontal caving range of the goaf decreases sharply, indicating that the filling body of the goaf can effectively prevent the collapse of the surrounding rock on the north side of the goaf, and this level can be considered as the critical filling level. Based on this, the scheme of the segmented filling governance of the goaf is proposed, which can effectively ensure the safety management of the goaf and the safe mining of the surrounding orebodies. [ABSTRACT FROM AUTHOR]