Jointed rock masses are a common phenomenon in rock engineering and are vulnerable to cyclic loads caused by earthquakes, blasts, and traffic loads.Therefore, it is crucial to comprehend the fatigue characteristics of jointed rock masses under dynamic cyclic disturbance for long-term stability assessments of rock engineering structures. This paper aims to investigate the effects of distinct joint inclinations under pre-cyclic loading on the strength and failure characteristics of rock-like specimens using experiments and numerical simulations. The results indicate that cyclic loading decreases the strength of the specimen, and the strength characteristics of the specimen are more apparent as the joint inclination angle becomes smaller. Furthermore, insights into different upper limit stress fatigue behaviors were gained by analyzing strength characteristics, crack propagation characteristics, and failure modes. Numerical results show that the damage degree of cyclic loading at high-stress levels is linked to the joint inclination angle and carrying capacity of specimens, and high cycle stress levels have an impact on the failure mode of the specimen.cyclic load, damage and failure, jointed rock, numerical modeling, particle flow Highlights 1. The damage degree of jointed specimens at different upper limit stress cyclic levels was investigated.2. The sensitivity of jointed specimens to cyclic stress-level damage was revealed.3. The macro and meso fatigue behaviors of jointed specimens were discussed.
In complex and extreme environments, such as pipelines and polluted waters, gait programming has great significance for multibody segment locomotion robots. The earthworm-like locomotion robot is a representative multibody bionic robot, which has the characteristics of low weight, multibody segments, and excellent movement performance under the designed gait. The body segment cell can realize large deformation under ultra-low frequency excitation. The multibody segment robot can locomote under ultra-low frequency excitation with appropriate shifts. In this paper, a modular gait design principle for a soft, earthworm-like locomotion robot is proposed. The driven modules defined by modular gait generation correspond to the peristaltic wave transmissions of the excitation in the robot for different modular gait modes. A locomotion algorithm is presented to simulate the locomotion of the earthworm-like robot under different locomotion gaits. Moreover, the locomotion speeds are obtained for different modular gait modes. The results show that locomotion speed is related to the original state of the body segments and modular gaits. As the initial actuated segments and driven modules (which correspond to the excitation frequency and shift) increase, faster movement speeds can be realized, which resolves the speed saturation of the earthworm-like robot. The proposed modular gait design method gives a new gait generation principle for the improvement of the locomotion performance of soft, earthworm-like robots.
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