Abstract:

The shattering deformation masses in high seismic intensity area are widely distributed. In order to understand the shattering failure mechanism of step-like bedding rock slopes under multi-stage earthquake excitations, a large-scale shaking table test is conducted based on the cut slope of Sanqing Expressway. The ratio of acceleration amplification factor (RAAF) is proposed to investigate the difference of acceleration dynamic response at different positions, while the Hilbert-Huang transform and marginal spectrum are used to identify the cumulative damage effect and failure process. Combined with the slope failure phenomenon, the shattering failure mechanism is clarified. The results show that the slope has an elevation amplification effect, and the acceleration amplification factor tends to increase first and then decrease with the increase of the input peak seismic wave. The RAAF undergoes a positive-to-negative mutation before and after the 0.6g input seismic wave peak, which is the critical value for changing the dynamic response between the two slope types. Under multi-stage earthquake excitations, the low-frequency component of the Hilbert spectrum decreases while the high-frequency component increases, indicating a filtering effect of rock mass and interlayer. Under horizontal seismic excitation, the internal corners of the step are easy to exhibit dynamic tensile stress concentration, resulting in the internal corners prone to be shattered. For the slope with uneven step width, the progressive failure processes involve the second step being shattered firstly, followed by the upper rock mass sliding along the weak interlayer, the rear edge of the slope top being pulled apart, and finally, the first step being pulled apart and separated from the slope body. For the slope with even step width, the cracks appeared at the internal corners of each step, while there was no obvious sliding surface. The shaking table test reveals the shattering failure mechanism of step-like bedding rock slopes. In survey, design, and construction, it is significant to pay attention to the deformation at the internal corners of each step and apply an arc treatment to reduce stress concentration. Additionally, anti-slip piles can be installed at the slope toe to increase the threshold for shattering failure and enhance stability of the rock slope.

Key words: multi-stage earthquake excitations, step-like bedding rock slope, shattering failure mechanism, shaking table test