Model tests were conducted to analyse the sliding stability of a retaining wall constructed by soilbags. The aim was to obtain an equation that calculates the active resultant earth pressure of sand acting on the wall in the ultimate state. Additionally, shear tests on multi-layers of vertically stacked soilbags were designed to investigate how the interlayer friction resistance varied with the height of the wall. The results show that the active earth pressure acting on the soilbag-constructed retaining wall in the ultimate state is non-linear, but it can be calculated from the force equilibrium of a differential element. The interlayer friction resistance of soilbags is found to be related to the shape of the sliding surface. Based on the obtained equation and the unique shear test results, the sliding stability of the retaining wall constructed by soilbags could be appropriately analysed.

A study was performed to investigate the bearing capacity of foundations reinforced by soilbags filled with excavated soft soils by conducting field load tests and numerical analysis. The effect of the number of reinforcement layers on the bearing capacity of the soilbag-reinforced foundation was investigated. Both the experimental and numerical studies indicated that soilbag reinforcement with reused excavated soft soils as the contained soilbag material can substantially improve the bearing capacity of the soft foundation and reduce settlement under vertical loading conditions. The bearing capacity was also found to increase with increasing number of soilbag reinforcement layers. The numerical analysis indicated that stress dispersion occurred through the soilbag reinforcement to reduce the load transferred to the underlying soft soils. High-quality compaction of the soilbag layers during construction is very important to improve bearing capacity. In addition, the excess pore water pressure generated in the soft foundation was less with the soilbag reinforcement and decreased with an increasing number of reinforcement layers due to the relatively high permeability of the soilbag reinforcement.

This research addresses the characteristics of soft soil subgrades treated by soilbags filled with excavated clayey soil. We evaluated of the strength and deformation modulus of soilbags containing excavated soil using unconfined compression tests. In addition, the drainage consolidation characteristics of soilbag-treated subgrades were investigated via model consolidation tests. Furthermore, a practical application included the construction of a 100 m-long rural road subgrade with these soilbags. The field test and numerical simulation results included the surface settlement and pore water pressure during and after construction to validate the effectiveness of the soilbag treatment for soft soil subgrade. The results show that the soilbags significantly enhanced both the strength and deformation modulus of the soft soil, which met the design requirements after the soilbag treatment. The drainage attributes of the soilbag treatment were also found to support the consolidation process of the soft soil subgrade effectively. Notably, the pore water pressure diminished rapidly during the construction interval, which is beneficial to reducing the post-construction settlement. The settlement uniformity of the subgrade is good verification of the superiority of the soilbag-treated subgrades.