In daily life, the human body inevitably encounters accidents such as falls and slips. Sudden high-rate loading under such circumstances may lead to a certain form of annulus fibrosus injury or rupture, yet the underlying injury mechanism remains unclear. This study quantitatively analyzed the mechanical mechanisms of lumbar intervertebral disc injury under high-strain-rate loading, while considering the influence of the degree of damage. A total of 56 ovine lumbar intervertebral disc specimens were prepared and divided into four groups (healthy, mildly damaged, severely damaged, and herniated) to measure their stress–strain curves at different strain rates. The results show that under high strain-rate loading, the elastic modulus, peak stress, and yield stress vary slowly with strain rate, and the rate of change is much lower than that under quasi-static loading. The elastic modulus, peak stress, and yield stress of all specimens decrease significantly with increasing injury severity, while the peak stress and yield stress rise rapidly with increasing strain rate. Magnetic resonance imaging (MRI) showed that, after compressive loading until rupture, the nucleus pulposus area is notably reduced in severely injured and herniated specimens, and nucleus pulposus extrusion is observed in some samples. In summary, the Zhu-Wang-Tang (ZWT) constitutive model is employed to characterize the viscoelastic mechanical behavior of lumbar intervertebral discs under high strain-rate loading, and a damage factor is introduced to describe the damage evolution. The fitted curves from the constitutive model agree well with the experimental curves. The results reveal the damage evolution patterns and mechanical mechanisms of the lumbar intervertebral disc under the combined effects of high strain rates and pre-existing damage levels, providing theoretical guidance for the analysis of lumbar intervertebral disc injury risk under dynamic loads such as falls and slips.
