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The synthesis of bistetrazole via a one-step process including substitution-cyclisation-cracking reaction has been reported for the first time. The combination of a nitrogen-rich energetic framework and a high oxygen detonation group perfectly fulfills the target of maintaining a high level of nitrogen content and good oxygen balance while avoiding the safety risks. H2TT, with 81.5% nitrogen content, demonstrates a very high heat of formation (DHf = 5.54 kJ g-1) and superior detonation velocity (D = 8932 m s-1) to RDX (D = 8795 m s-1). After the introduction of dinitromethyl high oxygen groups, the target compound BDNTT has an oxygen balance of -11.6% and a high crystal density up to 1.914 g cm-3, and exhibited superior detonation performance (D = 9633 m s-1, P = 41.4 GPa) to HMX (D = 9144 m s-1, P = 39.3 GPa). At the same time, the nitrogen content and oxygen balance of the BDNTT reached a decent level of 54.1% and -11.6%, respectively. Future researchers can use this study as experience to design advanced high-energy density materials. [ABSTRACT FROM AUTHOR]

The established research hotspots of shales, which play a significant roles in the stability of slopes, mainly focuses on its bedding plane effect under conventional stress paths, although landslides frequently suffer from complex stress disturbances. This study aims to investigate the effects of cyclic loading paths and interbed structure on the mechanical properties and energy evolution characteristics of shale. In the experiments, shale specimens with five types bedded angles (0°, 30°, 45°, 60°, and 90°) were prepared, and multilevel constant-amplitude cyclic loading (stress path Ⅰ) and multilevel increasing-amplitude cyclic loading (stress path Ⅱ) were performed. The results indicated that the mechanical behaviors including strength, deformation and failure modes, energy dissipation, and internal damping of shale samples were all highly affected by the bedding plane angles and the cyclic loading paths. Specifically, with the increasing of bedding angle, the peak strength, total dissipated energy, and total input energy of the shale specimens showed a "U" trend, the ultimate macro-failure mode changed from mixed tension-shear failure to failure along the bedding planes, and the damping ratio firstly increased and then decreased. In addition, test schemes of stepwise increase of the lower stress limit or keeping it constant were the differences between stress path Ⅰ and stress path Ⅱ, which significantly influenced the evolution of irreversible deformation of shale specimens. Peak strength of shale samples under stress path Ⅰ ranged from 4.3% to 23.9% lower than under stress path Ⅱ. Compared with stress path Ⅱ, elastic modulus and damping ratios of shales had the greater variations, under stress path Ⅰ, and dissipated energy and elastic strain energy were relatively low by an order of magnitude. [ABSTRACT FROM AUTHOR]

Roadways are common in infrastructure of the underground engineering. The surrounding rocks of these roadways are often allowed to work with flaws and are subjected to cyclic loading with variable magnitude. However, the existing experimental data regarding their behavior are insufficient. This study investigated how confining pressure and the inclination of pre‐existing fissures affect the mechanical properties and failure mechanisms of sandstones from the Lu‐Xi coal roadway in Shandong Province. Utilizing triaxial cyclic experiments along with real‐time acoustic emission (AE) monitoring, the findings were presented with respect to the evolution of strength as well as deformation behaviors, failure modes, and AE event frequency. Finally, the impact of the above two factors on damage mechanisms of preflawed sandstone materials were detailed discussed in terms of the fracture mechanics. This study highlights the importance the buried depth and flaws for the rock engineering and the sensitivity of sandstone's mechanical responses in changes in the lateral restriction and fissure angle. Highlights: Fatigue properties of fractured sandstone were investigated under cyclic loading.Mechanical parameter dropped and then rose as angle between intersecting flaw increased.The fatigue damage evolution of fractured sandstone was analyzed by AE parameters.The effect of flaw angle on mechanical behavior was explained by fracture mechanics. [ABSTRACT FROM AUTHOR]