Cementitous material based stabilization of soft soils by stabilizer: Feasibility and durabiliy assessment

Abstract

To accurately assess the safety of excavation and its impact on deformation settlement in soft soil areas, it is essential to conduct stability analysis and investigate the solidification mechanism of improved soft soil. This study involved a comprehensive series of laboratory tests, such as direct shear, dry-wet cycles, scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests, encompassing a wide range of working conditions. Based on the findings, an optimal construction scheme for solidifying the soil was proposed, utilizing data from the Zhuhai Tunnel project. The test results indicated that the curing time and proportion significantly influenced the shear strength of the amended soil. It was determined that a 10% cement and 9% stabilizer curing for 28 days represented the optimal proportion. The stabilizer primarily enhanced the shear strength by increasing the cohesion of the soil. Furthermore, the improved soil exhibited excellent stability even after undergoing seven dry-wet cycles. Additionally, microscopic analysis was conducted to explore the chemical reactions and solidification mechanism occurring between particles in the improved soft soil. The stabilizer induces the migration of water molecules to the soil surface and continuously supplies hydration to the cement, promoting its secondary hydration and generating more calcium silicate hydrate gel (C-S-H) and ettringite (AFt). The gelation and filling effects of the hydration products between particles resulted in a densified structure, thereby enhancing the mechanical strength and stability of the improved soil. This research offers valuable guidance for the application of soil improvement in construction and engineering projects in soft soil areas.