Phase‐Transition Variations in Granular Materials Under Multi‐Period Vibrations: Implications for Triggering Landslides After Multiple Earthquakes

Abstract Earthquake‐triggered landslides are widely recognized. Despite extensive research on the seismic responses of landslides triggered by single earthquakes, there is a lack of understanding of the seismic responses of landslides due to earthquake sequences and multiple earthquakes, and the mechanisms of dynamic weakening under multiple earthquakes still lack support from experimental results. To explore their seismic response characteristics and triggering mechanism, a series of multi‐period vibrations ring shear tests and dynamic triaxial‐bender tests were conducted with glass spheres. The experimental results show that the co‐vibration slip occurred during the vibration process, and as the vibration periods increased, the sample gradually slipped after vibration, eventually leading to accelerated instability. The sample exhibited a transition from a solid‐semi‐solid state to a liquid state due to the increase in vibration periods. Further results show that the shear modulus progressively weakened with successive vibration periods. The weakening of the shear strength of the sample caused by multi‐periods vibration was affected by the amplitude, the vibration time, and the interval time between two periods of vibration. Our study provided insights into how multiple earthquakes of seismic sequence and seismically active area trigger landslides.