This paper presents a comprehensive analysis of the active earth pressure behaviour in narrow backfill retaining walls (NBRWs) subjected to translational movement, a condition often encountered in practical retaining wall applications. A plane-strain finite element model is developed to simulate the interaction between the retaining wall, backfill soil, and the adjacent rock face, incorporating realistic boundary conditions and soil constitutive behaviour. Numerical analyses are conducted for various aspect ratios (b/H = 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7), relative densities (Dr = 70%, 75% and 80%), rock face inclinations (70°, 75°, 80°, 85°, and 90°), and soil friction angles (25°, 26.6°, 28.2°, 29.8°, 31.4°, 33.0°, and 34.6°). The model is validated against recent large-scale experimental studies and benchmarked with analytical approaches and Coulomb’s classical earth pressure theory, uncovering a strong correlation across these solutions. It was noted from the results that the maximum active earth pressure at the base of the wall decreases from 4.85 kPa to 2.5 kPa as the aspect ratio (b/H) reduces from 0.7 to 0.2 for Dr = 80%, reflecting a 48.5% reduction due to increasing geometric confinement. Similarly, for Dr = 70%, the pressure decreases from 4.9 kPa to 2.53 kPa (48% reduction), and for Dr = 75%, from 4.8 kPa to 2.51 kPa (47% reduction). The earth pressure coefficient at the base reduces from 0.24 to 0.13, corresponding to a 45.8% decrease as b/H changes from 0.7 to 0.2. The total active earth pressure coefficient exhibits reductions of 18%, 22%, and 24% for Dr = 70%, 75%, and 80%, respectively, indicating a consistent decline in mobilised pressure with increasing relative density. With decreasing rock face inclination from 90° to 70°, the active pressure decreases from 4.57 kPa to 2.7 kPa, representing a 41% decrease, due to the increased confinement offered by the steeper rock face, which limits soil displacement and restrains lateral deformation behind the retaining wall. Numerical analyses reveal that configurations with b/H = 0.2 and b/H = 0.3 consistently develop three reflective failure surfaces, indicating that under constrained backfill conditions, the soil undergoes complex internal redirection. This finding, established through current simulations, marks a significant shift from the classical single-wedge assumptions and underscores the influence of geometric confinement on slip surface development. By integrating validated finite element simulations with experimental and analytical benchmarks, this study provides detailed insights into the pressure behaviour and failure mechanisms of NBRWs, with strong implications for the design and safety of retaining wall systems.

Active Earth Pressure on Retaining Walls with Narrow Backfill Adjacent to Rock Faces

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发表日期：

2025年12月9日

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S. Danish Bashir,
M. Roshan Khan,
B. Munwar Basha

摘要

This paper presents a comprehensive analysis of the active earth pressure behaviour in narrow backfill retaining walls (NBRWs) subjected to translational movement, a condition often encountered in practical retaining wall applications. A plane-strain finite element model is developed to simulate the interaction between the retaining wall, backfill soil, and the adjacent rock face, incorporating realistic boundary conditions and soil constitutive behaviour. Numerical analyses are conducted for various aspect ratios (b/H = 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7), relative densities (D_r = 70%, 75% and 80%), rock face inclinations (70°, 75°, 80°, 85°, and 90°), and soil friction angles (25°, 26.6°, 28.2°, 29.8°, 31.4°, 33.0°, and 34.6°). The model is validated against recent large-scale experimental studies and benchmarked with analytical approaches and Coulomb’s classical earth pressure theory, uncovering a strong correlation across these solutions. It was noted from the results that the maximum active earth pressure at the base of the wall decreases from 4.85 kPa to 2.5 kPa as the aspect ratio (b/H) reduces from 0.7 to 0.2 for D_r = 80%, reflecting a 48.5% reduction due to increasing geometric confinement. Similarly, for D_r = 70%, the pressure decreases from 4.9 kPa to 2.53 kPa (48% reduction), and for D_r = 75%, from 4.8 kPa to 2.51 kPa (47% reduction). The earth pressure coefficient at the base reduces from 0.24 to 0.13, corresponding to a 45.8% decrease as b/H changes from 0.7 to 0.2. The total active earth pressure coefficient exhibits reductions of 18%, 22%, and 24% for Dr = 70%, 75%, and 80%, respectively, indicating a consistent decline in mobilised pressure with increasing relative density. With decreasing rock face inclination from 90° to 70°, the active pressure decreases from 4.57 kPa to 2.7 kPa, representing a 41% decrease, due to the increased confinement offered by the steeper rock face, which limits soil displacement and restrains lateral deformation behind the retaining wall. Numerical analyses reveal that configurations with b/H = 0.2 and b/H = 0.3 consistently develop three reflective failure surfaces, indicating that under constrained backfill conditions, the soil undergoes complex internal redirection. This finding, established through current simulations, marks a significant shift from the classical single-wedge assumptions and underscores the influence of geometric confinement on slip surface development. By integrating validated finite element simulations with experimental and analytical benchmarks, this study provides detailed insights into the pressure behaviour and failure mechanisms of NBRWs, with strong implications for the design and safety of retaining wall systems.