Stress ratios in entire mine stopes with cohesionless backfill: A numerical study

Evaluation of stress states in backfilled mine stopes (or similar openings), using archingtheory, can be largely impacted by the value selected for the earth pressure coefficient, K = σ′h/σ′v.Recently, the current study's authors addressed the debate about the value of K near the openingcenter, based on Rankine's active coefficient (Ka) and at-rest coefficient (K0). Here, stress ratios invertical backfilled stopes are numerically assessed (in two dimension, 2D), considering both theindependent and related backfill internal friction angle (φ′) and Poisson's ratio (ν). Emphasis is placedon the backfill state near stope walls, where local rotation of stresses occurs, so the coefficient (K)and principal stress ratio, Kps (= σ′3/σ′1), should be distinguished. Parametric analyses indicate thatvalues of K and Kps depend on the position and the relationship between φ′ and ν. Near the openingcenter, K (= Kps) is close to Ka when ν or φ′ is below a critical value; otherwise the value approachesK0, defined from ν. Near both walls, Kps is always close to Ka, while K is near K0 for related ν − φ′cases and depends on their respective values for independent ν and φ′. Additional simulationsconducted with interface elements indicate that the stress ratios near the opening center line areinsensitive to interface roughness and are almost identical to values obtained without interfaces, butthe stress ratios near walls may change for less rough or smooth interfaces.

Uncontrolled Keywords

mine stopes; backfilled openings; earth pressure coefficient; principal stress ratio; FLAC