Analysis the feedback characteristics of sandstone during sliding process

The sliding system of a slope is a nonlinear mechanical system, in which slip surface wear and changes in system energy constitute a feedback process. To investigate the relationship between feedback characteristics and sliding stability during slope slip, the sliding friction tests were conducted on the sandstone specimens. The results revealed that the friction coefficient exhibits nonlinear variation duing the sliding process. A sliding model of sandstone along the slip surface was established to analyze the sliding behavior of the specimens. During sliding, the shearing of surface asperities is accompanied by a decrease in the friction coefficient, which continues to decline with increasing displacement. Energy dissipation occurs and there is also energy replenishment during the sliding. Within a period, the system’s energy sometimes large and sometimes small, exhibiting a cyclic process of dissipation and replenishment, resembling a tension-relaxation movement in the sliding system. The Van der Pol equation was employed to analyze the system’s dynamic characteristics. During sliding, the system continuously alternates between negative and positive feedback states, leading to a periodic energy pattern characterized by attenuation-growth-attenuation cycles. In addition, a feedback loop for the sliding friction process of the sandstone was established, and criteria for the occurrence of positive feedback is proposed: as the sliding velocity increases, the system’s energy decreases, indicating a positive feedback state. At this time, the system continuously releases energy, the sliding velocity is faster and faster, and the system is unstable.The feedback characteristics study can provide important support for the analysis of the evolution process of landslide disaster.