Strength and Micro- and Mesocharacteristics of Solidified Soft Soil under the Coupled Effects of Continuous Loading and Seawater Attack

This study investigated the coupled effects of loading levels and seawater exposure duration on the mechanical properties and degradation mechanisms of solidified marine soft soil. Employing a solidifier composed of soda residue (SR), ground granulated blast furnace slag (GGBS), and carbide slag (CS), the unconfined compressive strength (UCS) and micro- and mesocharacteristics of solidified soil under continuous loading and seawater attack were explored, with comparative analysis against preloading conditions. The results showed that under continuous loading in distilled water, the UCS of solidified soil increased with both loading levels and immersion duration. Conversely, in seawater environments, UCS demonstrated an inverse relationship with loading level, registering a significant 32% reduction when continuous loading increased from 0% to 40% after 14 days of seawater immersion. Comparative analysis showed that at a loading level of ≤40% with a short immersion period, the effects of preloading and continuous loading on UCS followed similar trends. However, high-level continuous loading combined with long-term exposure precipitated substantial strength deterioration. Notably, at 60% preloading with 120-day seawater immersion, the UCS of solidified soil exceeded 1,000 kPa, while samples under continuous loading of >50% exhibited rapid strength degradation. Micro- and mesocharacteristic investigations revealed that continuous loading induced nonuniform pore distribution, transforming initial defects into preferential pathways for seawater intrusion. The synergistic action of continuous loading and seawater attack generated excessive formation of AFt and Fs, resulting in a looser microstructure with uneven and complex pore distribution, thereby exacerbating deterioration. These findings underscore the importance of ensuring homogeneity in solidified soil construction practices and the necessity of incorporating loading conditions in the design for solidified soil deployed in aggressive marine environments.