Active Earth Pressure of Narrow Backfill against Inverted T-Type Retaining Walls Rotating about the Heel

Inverted T-type retaining walls are commonly used in subgrade or slope support engineering, which inevitably satisfies a narrow backfill. Using the classical earth pressure calculation method in a narrow-backfill case causes an inevitable error. The current narrow-backfill earth pressure theory does not apply to inverted T-type retaining walls. In this study, the failure mechanism in a narrow backfill when the inverted T-type retaining wall rotates about the heel is investigated using adaptive finite element analysis method. Numerical analysis reveals multiple sliding surfaces. A theoretical model for calculating earth pressure using difference and limit equilibrium methods is proposed. The proposed model is suitable for more complex conditions, including narrow backfill, irregular ground, and non-uniform overload, than previous models. Parameter analysis reveals that the cross-sectional area of the plastic zone and active earth pressure have a positive correlation. Further, the interface friction influences the decrease in active earth pressure. Fitting formulas for assessing the cases of long and short heel and the critical size of backfill width are presented to facilitate practitioners to evaluate the backfill.