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In the coal measure strata, igneous rocks are often invaded, and their occurrence, size, and distribution form play an important role in mining safety. The breakage of hard and thick igneous rocks easily induces dynamic disasters, such as rock burst, mine seismicity, gas outburst, and surface subsidence, which seriously threaten mine safety production. In view of the working face with overlying hard and thick igneous rocks, the evolution characteristics of mining stress and energy distribution under hard and thick igneous rocks were investigated. Furthermore, the influence law of different horizons and thicknesses of igneous rock on overlying strata movement law, stress distribution, and energy distribution was analyzed based on FLAC3D numerical simulation. Results show that no evident subsidence of the overlying strata exists before the igneous rock is broken. Additionally, the subsidence amount of the overburden is suddenly increased after the igneous rock is broken, thereby showing significant mutability. Before the igneous rock breaks, a high stress area is formed around the goaf, and the stress concentration gradually increases with the increase of the mining scope. After the igneous rock breaks, the coal under high stress is prone to induce dynamic disasters under the action of strong dynamic load. However, the advanced abutment pressure and stored energy rapidly decreased. The accuracy of the numerical simulation is verified by field monitoring. Results of the study are of considerable significance for safe mining of working face under similar geological conditions.

Based on the analysis of dynamic phenomena under the condition of high-located hard-thick (HLHT) stratum of one coal mine, along with the similar material simulation and theoretical analysis, the characteristics of bed separation development and cracks distribution under the HLHT stratum are studied. This paper proposes a discriminating method for overlying strata Three Zones considering the influence of HLHT stratum. The development laws of cracks and disaster-causing mechanism of hard-thick magmatic rock in different strata are respectively analyzed. The studies show that in line with the working face advancing direction, the height of bed separation under the magmatic rock increases in the trend of “Increase–Stability–Decrease”, and the width of bed separation increases linearly. The width of bed separation reaches the maximum before the first breaking of magmatic rock, the bed separation completely closes after the breaking. There are no obvious bed separations during the period migration of magmatic rock. Along the direction of the height of roof, the development of bed separation is characterized by bottom-up jump based on the key strata. The analyzed results of “Three zone” height obtained by the discriminate method of overlying strata Three Zones which is based on the key strata theory and the S–R instability theory are in line with the actual facts. When the hard-thick magmatic rock is in the fractured zone, large amounts of gas and water are easy to accumulate in the bed separation space and “O” ring space around the gob. The first breaking of magmatic rock may induce bed separation gas outburst and water inrush. When the hard-thick magmatic rock is in the sagging zone, the long-term stability of magmatic rock will not cause serious disasters. But with the adjacent working face mining, bed separation gas and water often become a safety hazard.

Based on the boundary support conditions of overlying high-position, hard and thick strata, a Winkler foundation beam mechanical model was built. Computational expressions for the characteristics and position of the bending moment for high-position, hard and thick strata were constructed by theoretical analysis, and the initial breaking position of high-position, hard and thick strata was also analyzed. The breaking process and evolution law of mining stress in high-position, hard and thick strata were studied by similar material simulation tests. Studies show that: due to the foundation deformation effect of the lower strata, the initial break position in high-position, hard thick layers is in the middle of goaf; vertical tension fractures first occur under the middle surface, then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation; behind the coal wall tilt fractures extend and eventually complete the migration. Mining stress produces obvious changes before and after the breakage of the high, hard and thick stratum; high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration. Coal seam mining under high-position, hard thick strata can easily induce dynamic phenomena. Keywords: High-position hard and thick strata, Elastic foundation, Initial breaking, Breaking process, Mining-induced stress

The impact trend of rock-coal system was studied by the method of accumulating and releasing of deformation energy and interaction of rock-coal system. The system model of roof-coal-floor was established. Based on the RFPA software, rock fracture process analysis system, the numerical test of deformation, fracture and energy transmission of nonlinear and nonhomogeneous rock-coal system, and the numerical test and evaluating method of impact trend of rock-coal system were achieved. When the same coal seam was in different roof and floor conditions, the fracture process of rock-coal system can be classified as gradual, sudden and delayed fracture three kinds, and their impact trend can be classified as void, intense and medium correspondingly. The rock-coal system’s impact trend is evaluated by the system impact index µ and burst expanding forms. The criteria µ are µ

To investigate the clinical features of diffuse brain swelling following severe craniocerebral trauma and explore the optimized treatment protocols.A total of 134 cases of craniocerebral trauma with diffuse brain swelling receiving surgical treatment (n=76) and conservative therapy (n=580) were analyzed retrospectively for the clinical outcomes.Of the 76 surgical patients, 55 survived with a survival rate of 72.4% as compared with the rate of (75.9%, 43/58) in the conservative therapy group.Early implementation of comprehensive measures is of critical importance in the management of severe craniocerebral trauma with diffuse brain swelling.