The counterpressure pile sheet retaining walls are a novel type of slope support structure. Although engineering practice has demonstrated their excellent performance

systematic studies on their deformation characteristics and mechanical behavior remain limited. Through model tests comparing counterpressure piles and cantilever piles

this study investigates the evolution of pile-top displacement

pile deformation

internal force distribution

and earth pressure during the sandy backfill process. Key findings are as follows: (1) The top displacement of the cantilever pile was 81.76 mm

which is 6.69 times that of the counterpressure pile (12.22 mm)

resulting in cracking in the soil mass 51 cm horizontally away from the pile top. (2) The counterpressure pile exhibits a typical S-shaped distribution of bending moment

with a distinct reverse bending phenomenon and a reduction in the peak moment. (3) The excessive deformation of cantilever piles leads to an increase in the gravitational component of soil weight perpendicular to the pile shaft direction. The soil pressure on the counter-pressure pile is about 15% lower than that on the cantilever pile

reflecting its good stress redistribution ability. (4) Three primary working mechanisms are identified: provision of anti-overturning moment through soil reaction on the counterpressure plate

enhancement of horizontal resistance via friction between the plate and soil

and increase of passive earth pressure in front of the pile. The counterpressure platform significantly enhances overturning resistance

mitigates slip

and improves long-term structural stability. These findings offer experimental validation and a theoretical basis for optimizing counterpressure pile sheet retaining wall designs.