Salt-frost heaving of canal foundation saline soils is the primary cause of damage to the lining structures of water conveyance channels in the Hetao Irrigation District, China. Chemical solidification of saline soils can mitigate frost heave; however, application studies exploring the salt-frost heave resistance of saline soils solidified through the synergistic use of multiple industrial solid wastes in the Hetao remain limited. This study employs a sustainable solidifying material composed of slag, fly ash, coal gangue, coal-based metakaolin, carbide slag, and potassium silicate activator. The optimal mix ratio was determined using Response Surface Methodology (RSM). Unidirectional freezing tests evaluated the effects of solidification material content, curing period, and salt content on salt-frost heave development. Unconfined compressive strength tests assessed salt-frost heave durability of high-salinity solidified saline soils. Microstructural characteristics were analyzed using Scanning Electron Microscopy (SEM), Mercury Intrusion Porosimetry (MIP), X-ray Diffraction (XRD), and Thermogravimetric Analysis (TG) to investigate resistance mechanisms. Results indicated that the industrial waste materials exhibited synergistic effects in an alkaline environment, with the optimal mix ratio of slag, fly ash, coal gangue, coal-based metakaolin, carbide slag, and potassium silicate at 21:25:33:8:7:6. Increasing solidified material content and curing time significantly enhanced salt-frost heave resistance, as evidenced by improved freezing temperature stability, deeper freezing front migration, and reduced salt-frost heave rate. The optimal group (35 % solidifier, 7 days curing) showed a 5.53 degrees C increase in stable freezing temperature, a 3.78 cm upward migration of the freezing front, and a 3.94 % reduction in salt-frost heave rate. Salt-frost heave durability of highsalinity soils improved post-solidification, with a gradual decrease in the degradation of unconfined compressive strength, achieving a minimum weakening of 21.13 %. Hydration products C-S-H, C-A-H, and AFt filled voids between soil particles, restricting water and salt migration. Hydration of industrial wastes reduced free water and SO24 content, decreasing water-salt crystallization and mitigating salt-frost heave. The findings provide an engineering reference for in-situ treatment of salt-frost heaving in saline soils of water conveyance channels in the Hetao Irrigation District.

Infrastructures built on sulfate saline soil foundations in seasonal frozen regions are highly susceptible to saltfrost heave damage and salt corrosion. To address this issue, a method has been proposed utilizing a ternary blend of industrial solid waste materials - fly ash (FA), silica fume (SF), and brick powder (BP) - in conjunction with Portland cement (PC) for the solidification of sulfate saline soil. The feasibility of this solidification technique has been validated through a series of tests, including unconfined compressive strength tests, freeze-thaw cycle tests, salt leaching tests, and microstructural analysis. The results showed that: The unconfined compressive strength of the solidified saline soil at 56 days increased by up to 61.27 times compared to untreated saline soil. During the freeze-thaw cycles, the volume of salt-frost heave in the solidified saline soil was only 10.75% of that in untreated soil, with a reduction in salt-frost heave force by up to 90.94%. Furthermore, during the salt leaching process, the rate of salt migration in the solidified saline soil could be slowed by up to 4.15 times, while the total amount of salt leached was only 31.34% of that in untreated saline soil. Additionally, through the combined use of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS), it was discovered that the interactive synergistic effect of the solidifying agents in a SO42- rich environment facilitated the dissolution of Si-O and Al-O micro-lattices on the surface of the solidifying agent particles. This led to the extensive formation of C-(A)-S-H gels and AFt products, resulting in the transformation of the soil structure from dispersed to flocculated. The comprehensive test results indicate that the mechanical properties, frost resistance, and salt corrosion resistance of the solidified saline soil have significantly improved, with an optimal solidifying agent mixture ratio of 3% PC, 5% FA, 5% SF, and 6% BP. These findings can provide a reference for the solidification treatment of sulfate saline soil foundations in seasonal frozen regions.

In addressing the issue of strength degradation in saline soil foundations under the salt-freeze coupling effects, a binary medium constitutive model suitable for un-solidified and solidified frozen saline soil is proposed considering both bonding and friction effects. To verify the validity of the constitutive model, freezing triaxial tests are carried out under different negative temperatures, confining pressures, and water contents. The pore structure and fractal characteristics of saline soil are analyzed using mercury intrusion porosimetry (MIP) and the fractal dimension D qualitatively and quantitatively, which shed light on the strength enhancement mechanism during the solidification of frozen saline soils. The results show that the constitutive model for frozen solidified saline soil based on binary medium theory aptly captures the stress-strain relationship before and after the solidification of frozen saline soil. The stress-strain relationship of frozen saline soil before and after solidification can be delineated into linear elasticity, elastoplasticity, and strain-hardening or -softening phases. Each of these phases can be coherently interpreted through the binary medium constitutive model. The un-solidified and solidified frozen both show pronounced fractal characteristics in fractal analysis. Notably, the fractal dimension D of the solidified saline soil exhibits a significant increase compared to that of un-solidified ones. In Regions I and III, the values of D for solidified saline soil are lower than those for untreated saline soil, which is attributed to the filling effect of hydration products and un-hydrated solidifying agent particles. In Region II, the fractal dimensions DMII and DNII of the solidified saline soil exhibit a non-physical state, which is mainly caused by the formation of a significant number of inkpot-type pores due to the binding of soil particles by hydration products.