Field application and microscopic reinforcement mechanism of electrochemical technology for weak interlayer soft rock slopes in open-pit coal mines

Abstract

Soft rock slopes containing weak mudstone interlayers in open-pit coal mines easily experience subsidence-sliding failure. The weak interlayers feature low permeability and inferior mechanical properties, which severely threaten open-pit mining safety. Traditional reinforcement methods including bolt support and cement grouting suffer from weak penetration capacity and high construction cost, and cannot realize targeted consolidation of deep weak interlayers. To address this geological hazard issue, this paper proposes an optimized electrochemical reinforcement method suitable for low-permeability soft rock slopes in open pits, combining field tests, real-time electrical monitoring, numerical simulation and multi-scale microscopic tests. A soft rock slope with mudstone weak interlayers at an open-pit coal mine in eastern Inner Mongolia was taken as the research prototype. Optimized electrode arrangement and matched chemical grout ratio were adopted to carry out electrochemical reinforcement on weak interlayers. Real-time monitoring was conducted to record electrical parameter evolution during reinforcement. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were adopted to characterize mineral phase transformation and microstructural variation of reinforced rock mass. The average current rose from 200 A to 500 A in the grouting stage. Three coupled factors account for this current growth: ion-rich grout improving stratum conductivity, electroosmotic drainage compaction reducing pore channels and elevating current density, and continuous electrochemical hydration releasing conductive ions, rather than electrolyte concentration alone. After reinforcement, rock cohesion increased by 1.22–1.51 times, and internal friction angle grew by 1.29–1.54 times. Microscopic observations verified the generation of ettringite (AFt), hydrogarnet (AFm) and flocculent Al-Si-P gel, which fill internal pores and form stable cementation frameworks. Numerical simulation indicates the slope safety factor rises from 1.15 to 1.32, eliminating potential sliding instability. Electrochemical reinforcement relies on two coordinated stages: electroosmotic drainage consolidation and electrochemical cementation. The proposed technology supplies an effective control scheme for soft rock slopes with weak interlayers in open-pit mines. It expands the application scope of electrochemical reinforcement in mine geological disaster prevention, and provides theoretical and engineering references for analogous slope treatment projects.