Optimizing Concrete Retaining Wall Design: A Parametric Study on Soil Friction and Toe-to-Heel Ratio

Concrete Retaining Walls (CRWs) remain the most widely used system for stabilizing the earth slopes; however, their safety margins depend on both the soil properties and base geometry. Although numerous analytical and numerical studies have been conducted, the combined influence of the backfill shear strength and Toe-to-Heel (T:H) proportioning on the global stability has not been quantified across the height range, typical of transportation and infrastructure projects. This study addresses this gap by evaluating how the backfill friction angle and T:H affect the Factors of Safety (FS) against sliding, overturning, and bearing-capacity failure for walls 4 m to 10 m in height. A series of wall configurations was analyzed using closed-form limit-equilibrium equations that incorporate Rankine active earth pressure and eccentric footing stresses. The results show that increasing the backfill friction angle lowers the active pressure coefficient nonlinearly, increasing the sliding and overturning factors by up to 150% for 10 m walls and postponing the bearing failure by approximately 2 m in height. Extending the heel (T:H ≈ 0.5) provides up to a two-fold increase in the sliding and overturning resistance relative to a toe-dominant base, whereas lengthening the toe alone produces only marginal gains and has little impact on the bearing safety. Thus, the current study provides quantitative guidance that enables designers to trade off the soil quality and geometric proportions for a safer and more economically retaining wall construction.