Abstract:

To investigate the instability of rock slopes along joint surfaces in water-impounded abandoned open-pit mines under fluctuating water-level conditions, physical model tests were performed using similar materials containing joints and weak interlayers. The mix proportion of the similar materials was optimized through orthogonal experimental design to ensure that their mechanical and seepage properties corresponded to those of the in-situ rock mass. Multiple types of sensors were embedded in the model to monitor pore water pressure, earth pressure, moisture content, and displacement, enabling systematic observation of the multi-field responses of the slope during water-level fluctuations. Working conditions with different numbers of cycles and varied rates of water-level change were designed to examine the deformation characteristics and failure mechanisms of the slope. The results indicate that certain damage to the slope surface is caused by the scouring effect induced by repeated water-level fluctuations at a constant rate, although internal structural damage is limited. This suggests that overall stability is little influenced by slow, single water-level fluctuations. The rate of water-level change is shown to significantly affect slope behavior, with slope displacement increases positively correlated with the rate of water-level decline. Furthermore, the greater the outward-directed pore water pressure of the slope is, the more significantly it is influenced by the hysteresis effect, and the higher likelihood of slope instability becomes.

Key words: water level rise and fall, open-pit mine, rock slope, deformation failure, similar materials, model test