露天矿堆场中压实粘土在三轴剪切渗流试验中的渗透响应与机制

Permeability response and mechanis ms of compacted clay in open-pit mine dumps under triaxial shear-seepage testing

Lihui Qi¹,Xuedong Wang¹,Yuanjie Hou¹,Jin Li¹,Guangwei Liu¹ 

Abstract: This study investigates the pore structure evolution and permeability mechanis ms of compacted clay in dumps during shear deformation, providing critical insights for resource development, hazard prevention, and ecological restoration. Focusing on Yuanbaoshan mine’s inner dump clay in Inner Mongolia, we used triaxial shear permeability testing, MATLAB fitting, and MatDEM discrete element development and simulation to explore permeability evolution under varying compaction densities and confining pressures during shear. Results demonstrate that the permeability of compacted clay evolves through three distinct stages—rapiddecline,gradual decline,and stabilization—with increasing shear strain.The initial stage features  abrupt permeability reduction driven by particle rearrangement and pore collapse, followed by a decelerated decline phase where fine particles migrate to fill pores, ultimately reaching permeability stabilization. Under identical conditions, elevated confining pressure enhances deformation adaptability while higher compaction density reduces permeability; both factors nonlinearly suppress permeability by altering soil pore structure, with their influence most pronounced at low strains. During shear seepage, pore water pressure progressively decreases with time and axial strain before stabilizing, accompanied by downward and lateral particle displacement where migrating fine particles fill pores to reduce permeability. Concurrently, particle interlocking and bond breakage increase pore water pressure and decrease permeability. Increasing strain densifies lower particles, forming localized low-permeability zones with reduced water pressure. Thermally, initial spring heat accumulation drives compaction permeability plunge, while linear viscous and slipping heat growth accompanies uniform particle motion andstable permeability. These reveal the seepage suppression mechanis m viaprogressive densification and shear localization dominated flow anisotropy, providing theoretical/technical support for geotechnical practices.

Keywords: Inner dump; Compacted clay; Permeability coefficient; Triaxial shear penetration test; MatDEM 

Fig.2 SLB-1 stress–strain-controlled triaxial shear permeability tester and test principle diagram

Fig.4 Schematic diagram of discrete element particle contact and water migration

Fig.5 Discrete element specimen model

Fig.7  Post-testing morphology of specimen with ρdmin=1.54 g/cm3 after triaxial shear-seepage testing

Qi L, Wang X, Hou Y, et al. Permeability response and mechanis ms of compacted clay in open-pit mine dumps under triaxial shear-seepage testing[J]. Computational Particle Mechanics, 2025, 12(5): 4183-4203.