Analysis on time-frequency characteristics and construction response of microseismic events on high and steep rock slopes: A case study of Dongzhuang Water Conservancy Project

Abstract

The right bank slope of the Dongzhuang Water Conservancy Project is steep and high, with numerous dissolution cavities and mud-filled cracks forming reasonably well in the solid limestone, complicating the geological conditions and emphasizing the slope stability issue. To clarify the activation characteristics of various weak structural planes in the rock mass of the right bank slope under the influence of geological defect treatment and high-pressure grouting disturbance and to evaluate the overall stability of the slope, a real-time monitoring system for micro-seismic activity in both the deep and shallow parts of the slope rock mass was used, combining core drilling and colored borehole television technology. A generalized β wavelet high-resolution time-frequency transformation algorithm was used to analyze the dynamic micro-seismic response and damage characteristics of the slope rock mass under different engineering disturbances. The results reveal that: (1) The rock mass on the right bank slope deteriorates as a result of limestone breakdown and local mineral infill, while its plastic properties improve. Microseismic events have an amplitude of 0.06 mV and low energy, and their frequency is primarily focused between 100 and 300 Hz, with low-frequency vibrations dominating. (2) During drilling disruption, the micro-fractures on both sides and the deeper areas of the Rnj3 dissolution-mud-filled fracture become much stronger than before drilling. The lateral fracture surface of the Rnj3 dissolution-mud-filled fracture and the bottom slip surface of the L61 fracture have a weak temporal and spatial link during micro-crack development, and the energy release level is low. As the microseismic activity of the downstream L61 fracture reduces, the prospective sliding body’s slip risk is reduced. (3) During the early grouting stage, the high-pressure slurry washed out the muck from the mud-filled fracture. This caused localized dislocation instability of the neighboring rock mass, resulting in micro-seismic event clusters scattered along the fracture zone. After grouting, there were fewer micro-seismic events at an elevation at a height at the Rnj3 mud-filled crack, indicating low rock mass activity. By the middle of grouting, the formation of microseismic events has stopped, and the surrounding rock was stable under the consolidating impact of the grout. The findings serve as a key guide for curtain grouting reinforcement of steep slopes and other comparable projects.