Abstract
Evaluation of stress states in backfilled mine stopes (or similar openings), using arching theory, 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 opening center, based on Rankine’s active coefficient (Ka) and at-rest coefficient (K0). Here, stress ratios in vertical backfilled stopes are numerically assessed (in two dimension, 2D), considering both the independent and related backfill internal friction angle (ϕ′) and Poisson’s ratio (ν). Emphasis is placed on 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 that values of K and Kps depend on the position and the relationship between ϕ′ and ν. Near the opening center, K (= Kps) is close to Ka when ν or ϕ′ is below a critical value; otherwise the value approaches K0, 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 simulations conducted with interface elements indicate that the stress ratios near the opening center line are insensitive to interface roughness and are almost identical to values obtained without interfaces, but the stress ratios near walls may change for less rough or smooth interfaces.
Highlights
Backfilling mine wastes into stopes has become a common practice in underground mines worldwide [1,2,3]
It can be seen that the stresses near the walls were lower than those at the center. These indicate that the values of K along the vertical center line (VCL) and near those at the center. These indicate that the values of K along the vertical center line (VCL) and near rock walls (RW) could be different
The results presented above beenElements obtained from numerical simulations conducted without interface elements between the backfill and rock walls
Summary
Backfilling mine wastes into stopes has become a common practice in underground mines worldwide [1,2,3]. Arching theory has been commonly used to evaluate the stress state in backfilled mine stopes and various similar openings (silo, trench) [8,9,10,11]. The vertical (σ0 v ) and horizontal (σ0 h ) effective stresses in two-dimensional backfilled openings with cohesionless fills are often estimated from the following arching solution based on [9]: σ0 v = Bγ − exp h. K (= σ0 h /σ0 v ) is the earth pressure coefficient, defined as the stress ratio of the horizontal over vertical. The ratio of the horizontal to vertical stresses may correspond to the Rankine’s active earth pressure coefficient (Ka ), defined as follows for cohesionless soils with a horizontal surface and smooth walls: Ka =
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