冲击荷载下多层组合煤岩体的动态响应与破坏模式

Dynamic response and failure mode of multi-layered combined coal mass under impact loading

Abstract: Based on the proposed multi-layered combined coal mass model, specimens with single layer thickness of 2.5 cm are prepared. Drop-hammer impact tests are conducted to research the failure of coal mass, which is dominated by circumferential cracks, radial cracks and petal-shaped fragments. To clarify the failure characteristics, strain gauges are mounted on specimen sur faces to record the transient strain responses. The results show that, on the surface of Layer 1, the radial positions exhibit an initial compressive strain followed by tensile strain, whereas the circumferential positions show the opposite trend, i.e., tensile strain followed by compressive strain. On side surface, compressive strain develops along the impact axis, while tensile strain is observed at radial positions. To quantify the internal dynamic response, pressure sensors are embedded within coal mass, making the three-dimensional propagation of the stress wave to be identified. The numerical model of drop-hammer impact coal mass is developed using MatDEM, which the time-dependent evolutions of σz and displacement are obtained. Based on stress wave theory, the drop-hammer impact model is simplified. It’s found the unloading-wave generated during impact catches up with the preceding plastic loading-wave, the catch-up unloading pro duces internally reflected tensile stress wave, which promotes crack initiation and development. The spatial distribution of cracks induced by catch-up unloading is further examined from both transverse and longitudinal directions. An integrated failure mode of coal mass subjected to external impact disturbance is proposed, the causes of failure characteristics are clarified and providing reference for further clarifying the failure mechanism.

Keywords: Multi-layered combined coal mass model；Circumferential cracks；Transient strain responses；MatDEM；Stress wave；Failure mode

Fig.1 Self-developed true triaxial drop-hammer impact testing system.

Fig.4 Schematic of strain-gauge locations.

Fig.6 Arrangement of pressure sensors in the specimen.

Fig.7  Failure characteristics of each layer of the multi-layered combined coal mass after drop-hammer impact.

Fig.30 Distribution characteristics of the damage zone induced by drop-hammer impact in the multi-layered combined coal mass.

Wang C, Li F, Liu D, et al. Dynamic response and failure mode of multi-layered combined coal mass under impact loading[J]. Engineering Fracture Mechanics, 2026: 112373.