# Mechanism and Application of Soilbags Filled with Excavated Soil in Soft Soil Subgrade Treatment
###### Abstract  
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 signifcantly 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. geosynthetics: soilbag: soft soil subgrade treatment; field study: drainage consolidation Article  
Soilbags Filled with Excavated Soil Soil Subgrade Treatment  
posed by landfilling this sludge, several methods have been developed by geotechnical specialists to enhance the strength and deformation characteristics of the excavated soft soil. This, in turn, allows for the treated soil to be repurposed directly within engineering projects. These methods include electro-osmotic consolidation [7; 8], vacuum preloading [9], soil stabilization with lime and cement [10; 11; 12; 13], and geosynthetic reinforcement [14; 15; 16; 17]. Among these methods, geosynthetic treatment is notably recognized for its cost-effectiveness and environmentally friendly attributes [18; 19]. Consequently, it has been increasingly adopted for the treatment of soft soils in road construction. Geotextiles and geomembranes, which are the two primary categories of geosynthetics, are commonly integrated horizontally within foundations and subgrades for the remediation of soft soils [20; 21]. In a series of bearing-capacity tests on soil reinforcement with soilbags, it was discovered by [PERSON] and [PERSON] [22] that soils contained in geotextile bags are more effective and dependable than those reinforced using the conventional horizontal sheet method. They suggested that the increased strength of the contained soils can be attributed to the tensile force exerted by the geotextile containers under external pressure, leading to enhanced confinement in both the vertical and lateral directions. This mechanical behavior of soilbags was later numerically replicated and confirmed by [PERSON] et al. [23] and [PERSON] et al. [24]. In recent studies, applications of soilbags in geotechnical engineering practices, such as slope repair [25] and retaining wall [26] construction, have been reported. A notable application is the construction of a 100 m-long retaining wall in Suzhou, China, which utilized soilbags filled with excavated soft soil [27]. Inspired by this successful utilization of soilbags filled with excavated soil for retaining wall construction, this paper presents a solution that makes full use of the excavated residual soils for soft soil subgrade treatment on-site: to fill soilbags with the excavated residual soil to treat the soft soil subgrade. Previous research has mainly focused on the mechanical properties of conventional soilbags filled with coarse granular materials or low-cohesion soils, like sands, gravels, and loamy soils. The engineering properties of soilbags filled with excavated residual soil for subgrade treatment in road engineering are seldom mentioned.