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<p>This study investigates the active earth pressure distribution and failure mechanisms of narrow backfill retaining walls (NBRWs) subjected to rotational movement using large-scale laboratory experiments. The tests evaluate the influence of aspect ratio (<i>b/H</i> = 0.2 to 0.7) and relative density (<i>D</i><sub><i>r</i></sub> = 70, 75, and 80%) on active earth pressure behaviour. A retaining wall of 1.2&#xa0;m height is rotated incrementally to simulate field conditions, while advanced instrumentation captures wall displacements, earth pressure variations, and the development of failure surfaces. Results reveal that experimental active earth pressures are significantly lower than Coulomb’s prediction of 5.16&#xa0;kPa at z/H = 0.92. Specifically, active earth pressure values are 2.68, 3.53, 4.12, 4.42, 4.76, and 5.01&#xa0;kPa for b/H = 0.2 to 0.7, showing reductions of 48, 31, 20, 14, 8, and 3%, respectively. Correspondingly, active earth thrust increased from 1.820 to 2.726&#xa0;kN across the same b/H range. The total active thrust shows a maximum reduction of 34.8% at b/H = 0.2 (<i>P</i><sub><i>a</i></sub><sup><i>exp</i></sup> = 1.820 kN vs Coulomb's <i>P</i><sub><i>a</i></sub> = 2.796 kN) and converges to within 2.5% at b/H = 0.7. These findings confirm that lower aspect ratios lead to significant overestimation of thrust by Coulomb’s theory, risking over-design. Additionally, the total active pressure coefficient (K<sub>a</sub>) was reduced by 33, 34, and 36% for relative density (D<sub>r</sub>) = 70, 75, and 80%, respectively, at b/H = 0.2. These reductions decrease with increasing b/H, highlighting that wall spacing and compaction quality critically affect NBRW behavior. The deviations from linear pressure profiles at low b/H, particularly near the base, underscore the need for advanced design models that incorporate nonlinearity and geometric constraints. The findings are compared with the multi-wedge theory, which provides closer agreement with observed results than the classical approach. This study offers valuable data to support the design of NBRWs in constrained environments such as urban areas and hilly terrains, where conventional design methods may lead to inaccurate estimation of earth pressures.</p>

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Experimental Study of Active Earth Pressure on Narrow Backfill Retaining Walls Under Rotation

  • 期刊论文

  • 发表日期：

    2025年6月10日

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  • S. Danish Bashir,
  • B. Munwar Basha

摘要

This study investigates the active earth pressure distribution and failure mechanisms of narrow backfill retaining walls (NBRWs) subjected to rotational movement using large-scale laboratory experiments. The tests evaluate the influence of aspect ratio (b/H = 0.2 to 0.7) and relative density (Dr = 70, 75, and 80%) on active earth pressure behaviour. A retaining wall of 1.2 m height is rotated incrementally to simulate field conditions, while advanced instrumentation captures wall displacements, earth pressure variations, and the development of failure surfaces. Results reveal that experimental active earth pressures are significantly lower than Coulomb’s prediction of 5.16 kPa at z/H = 0.92. Specifically, active earth pressure values are 2.68, 3.53, 4.12, 4.42, 4.76, and 5.01 kPa for b/H = 0.2 to 0.7, showing reductions of 48, 31, 20, 14, 8, and 3%, respectively. Correspondingly, active earth thrust increased from 1.820 to 2.726 kN across the same b/H range. The total active thrust shows a maximum reduction of 34.8% at b/H = 0.2 (Paexp = 1.820 kN vs Coulomb's Pa = 2.796 kN) and converges to within 2.5% at b/H = 0.7. These findings confirm that lower aspect ratios lead to significant overestimation of thrust by Coulomb’s theory, risking over-design. Additionally, the total active pressure coefficient (Ka) was reduced by 33, 34, and 36% for relative density (Dr) = 70, 75, and 80%, respectively, at b/H = 0.2. These reductions decrease with increasing b/H, highlighting that wall spacing and compaction quality critically affect NBRW behavior. The deviations from linear pressure profiles at low b/H, particularly near the base, underscore the need for advanced design models that incorporate nonlinearity and geometric constraints. The findings are compared with the multi-wedge theory, which provides closer agreement with observed results than the classical approach. This study offers valuable data to support the design of NBRWs in constrained environments such as urban areas and hilly terrains, where conventional design methods may lead to inaccurate estimation of earth pressures.