Gas explosion accidents in underground coal mines caused a significant number of casualties. By using a large laneway test system, the damage to Sprague-Dawley (SD) rats at locations at different distances from the source of ignition along the direction of propagation of an explosion was investigated after 100 m 3 of the gas-air mixture was ignited and exploded. In this way, the data pertaining to explosion flames and explosion pressures at different propagation distances were obtained to investigate the propagation of explosion flames and explosion pressures along the laneway. Besides, the damage to SD rats at different propagation distances was statistically analyzed. Furthermore, the damage mechanism of explosion flames, explosion pressures, and hazardous gases on humans or animals was discussed. The results indicated that explosive blast injury induced by the gas explosion was the primary reason for the death of animals and SD rats at a distance equal to or greater than 80 m from the point of ignition under the effects of an explosive blast even though SD rats at a distance of 240 m were killed. During the explosion of 100 m 3 of mixed gas, the explosion flames propagated 40 m from the point of ignition, and the SD rats in the cage located some 40 m from the point of ignition were subjected to combined damage involving being burned at high temperature and suffering the effects of the explosive blast. These findings provide a theoretical basis for emergency rescue and salvage after gas explosion accidents in underground coal mines.

The deformation and instability of roadway surrounding rock reflect the processes of energy accumulation and release. To reveal the instability of roadway surrounding rock, based on the engineering geological conditions of a certain mine, this paper established a nonuniform superimposed stress model of a coal pillar, starting from the energy accumulation and release of the surrounding rock of the floor roadway after coal pillar failure. The essence of the deformation of the lower roadway was revealed, and the following conclusions were drawn: (1) The elastic strain energy accumulated in the lower roadway roof and upper coal pillar is related to not only the physical properties of the coal seam but also the distance between the coal pillar and surrounding rock, the caving height and shape, the burial depth, and the retained pillar width. (2) The elastic strain energy accumulated in the lower roadway roof and the upper coal pillar induced large displacements of the roadway due to the energy release during excavation. (3) It is proposed that the “stress relief degree” and failure morphology are used to identify zones in the rock and coal, and the two zoning modes have a high consistency. (4) The stress distribution in a narrow coal pillar should be calculated in segments. (5) Based on the zoning and energy release characteristics, the following control factors are suggested regarding the coal pillar width and roadway layout: (a) for the coal pillar, avoid the overlap or intersection of the peak values in the limit equilibrium zone and ensure a sufficient elastic zone; (b) arrange the roadway in shear slip Zone B-2 or the moderate pressure relief Zone B-2 to reduce the accumulation of elastic strain energy in the surrounding rock.

In this study, a uniaxial impact compression test was performed on coal samples with length-to-diameter ratios of 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 using a 50 mm split Hopkinson pressure bar (SHPB) test system. This study researched the stress uniformity and deformation behavior of coal samples with different ratios during dynamic compression, defined the stress equilibrium coefficient , proposed a new method for determining whether a sample meets the stress uniformity hypothesis, and obtained the critical ratio of 0.6 and the optimal ratio of 0.3 or 0.4 for coal samples to obtain the stress equilibrium. The experimental results showed that the dynamic stress-strain curve of coal had an elastic stage, a plastic stage, and a failure stage. As the ratio increased, the proportion of the elastic stage to the prepeak curve of the samples declined progressively; with an increase in the ratio, the peak part of the curve also changed from “sharp” to “stagnated,” while an increase in the plasticity led to strain softening. As the ratio of the samples increased, the average strain rate decreased approximately as a power function, and the decreasing trend was gradually reduced from 296.49 s −1 ( =0.3) to 102.85 s −1 ( =1), with a reduction of approximately 65.31%. With an increase in the ratio, the peak strain gradually decreased exponentially. This study concluded that the SHPB test protocol design is of a certain reference value for low-density, low-strength, heterogeneous brittle materials, such as coal.

Based on the variation range of the stress lode angle, the in situ rock stress is divided into - type stress field, - type stress field, and - type stress field. Through theoretical analysis, the principal stress difference distribution law and plastic zone distribution pattern around the roadway in different types of stress fields are obtained. Theoretical and numerical simulation calculation results show that under different stress lode angle conditions, the principal stress difference distribution of the surrounding rock of the roadway is greatly different, which has a direct effect on the shape and range of the plastic zone of the surrounding rock of the roadway. In the - type stress field and the - type stress field, the shape of the plastic zone of the roadway surrounding rock is mainly oval and “butterfly,” while in the - type stress field, the shape of the plastic zone of the roadway surrounding rock is mainly oval. The laboratory test proves that the stress gradient has an important effect on the damage degree of the surrounding rock of the roadway. The larger the stress gradient, the higher the strength of the rock mass and the more severe the damage. The change of the stress lode angle will affect the distribution law of the stress gradient of the surrounding rock of the roadway, thus affecting the degree of fragmentation of the surrounding rock. In type and type stress fields, the surrounding rock of the shoulder can be regarded as a key part of the roadway. In the - type stress field, the plastic zones of the surrounding rocks of the roadway are more evenly distributed, and the damage range is less affected by θ . The influence law of the stress lode angle on the stability of the roadway has been well verified by field observation, and effective support measures have been proposed.