The unloading pile-sheet retaining wall is a new type of support/retaining for embankment slopes and has demonstrated excellent performance in engineering applications. However, its mechanical behavior and operational mechanisms are still not fully understood. This study conducted model tests on unloading piles and cantilever piles. Backfilling was conducted in four stages: 30 cm for the first three layers and 10 cm for the final one. The tests focused on the evolution of earth pressure, internal forces, and deformation in both pile types. The results show that: 1) Upon completion of backfilling, the horizontal displacement at the top of the cantilever pile reaches 81.76 mm, which is 5.45 times that of the unloading pile (14.99 mm). The maximum earth pressure on the unloading pile is 10.08 kPa, accounting for 66.40% of the 15.18 kPa recorded on the cantilever pile. The unloading effect alters the distribution pattern and magnitude of earth pressure. 2) The bending moment distributions differ significantly. The cantilever pile exhibits a “fish-belly” pattern with a maximum moment of 115.8 N· m. In contrast, the unloading pile shows an “S-shaped” profile, featuring a pronounced point of contraflexure at the unloading platform and a maximum negative moment of −60.99 N· m. 3) Incorporating an unloading platform effectively reduces earth pressure and enhances the anti-overturning moment. These effects jointly improve sliding resistance and overall structural stability. These findings offer theoretical insights and technical guidance for the practical implementation of unloading pile-sheet retaining walls.

Soft soil has been a major problem in the northern part of Java for the last decade, and several areas have been improved using the preloading method. In Indonesia, the improvement of soft soil using this method has already been regulated in several codes, such as SNI 8460:2017 and Geotechnical Manual series 4. However, these codes did not mention the effects of creep on post-settlement. In addition to creep, several factors influence the amount of post-settlement during the operational period, such as the thickness of the soft soil, load ratio, soil compression ratio, and the drain spacing and pattern. Larger spacing or pattern, higher compression ratio, greater secondary compression index (C_α), and increased soft soil thickness induce more post-settlement. In contrast, a higher load ratio resulted in less post-settlement. It was discovered that the load ratio of 1.20 stated in SNI 8460:2017 did not meet the requirement of a maximum yearly settlement of 20 mm as specified in Geotechnical Manual series 4. This research showed that with and without creep, the load ratio required should be in the range of 1.30 to 1.50, with an average value of 1.375. Furthermore, this study proposed a new coefficient, the load ratio coefficient (C_LR), that accounts for various factors influencing post-settlement. The proposed coefficient can be utilized along with a period of interest to estimate the post-settlement due to creep. It was also observed that the load ratio heavily affects the post-settlement.