Experimental evaluation of the surcharge and loading shape on lateral earth pressure for retaining walls in coarse-grained gravel and sandy soils

The present study examines the parameters affecting drift due to soil reaction and the effects of factors such as the loading plate shape and soil type on the performance of retaining walls. The laboratory experiments were conducted with soil particle sizes of 0.249, 1.18, and 15 mm and three foundation shapes: circular, square, and rectangular - all with the same cross-section. The experimental results indicate the effect of soil particle size and shape on the lateral force. Soil with larger particles requires higher surcharge pressure to achieve the same settlement compared to other cases, and this will cause higher horizontal pressure on the wall. For the first tested soil, a settlement of 5 cm occurs with circular, square, and rectangular loading plates at pressures of 484 kPa, 416 kPa, and 594 kPa, respectively. However, a similar settlement occurs in the second soil at pressures of 165 kPa, 154 kPa, and 148 kPa, respectively. A third soil with different loading plates yields negligible pressure for a settlement of 5 cm. It was found that the maximum stress and strain occur in the backfill with the first soil with the maximum particle size and with circular, square, and rectangular plates at 60%, 84%, and 84% of the embankment height from the wall foot, respectively. Moreover, the maximum horizontal stress in this soil with circular, square, and rectangular foundations was estimated as 0.48%, 0.68%, and 0.48% of the vertical stress for a 5 cm settlement, respectively.