Binders can enhance soil properties and improve their suitability as subgrade fillers; however, the cementing effect and strength properties of solidified soil are highly susceptible to external environmental factors. This study evaluated the strength and durability of solidified sludge soil (PSCS) with varying binder (PSC) contents through unconfined compressive strength (UCS) tests combined with drying-wetting (D-W) and freezing-thawing (F-T) cycles, and identified the optimal binder content for performance enhancement. Additionally, mercury intrusion porosimetry (MIP) tests were conducted to analyze pore structure changes and explore the synergistic effects between hydration reactions and moisture variations induced by D-W/F-T cycles. Results indicate that binder content > 15 % significantly enhances PSCS strength and durability, with 15 % content (PSCS15) demonstrating the best economic advantage. During D-W/F-T cycles, the synergy between hydration reactions and moisture variations affects the pore structure, resulting in strength changes. For example, during D-W cycles, moisture movement causes the collapse of pores > 30 mu m, while hydration products fill the pores, decreasing the porosity of 5-30 mu m. Subsequently, moisture variations weaken the cementation effect, leading to a increase in the porosity of 5-30 mu m. This process causes the strength to fluctuate, showing a first decrease, followed by an increase, and then another decrease, with an overall reduction of 21.6 %. During the drying stage of D-W cycles, moisture evaporation inhibits hydration reactions in soil. In contrast, during F-T cycles, moisture remains in different physical states (e.g., solid ice crystals and liquid water). These moisture variations causing the collapse of pores >30 mu m, while hydration products fill the larger pores, increasing the porosity of 1-10 mu m. The strength first decreases and then increases, with an overall increase of 38.7 %. Furthermore, this study demonstrates that until the hydration process is completed, D-W cycles have a more significant negative impact on PSCS compared to F-T cycles.

Embankments and foundation geotechnical structures are frequently subjected to long-term cyclic loading due to traffic during their service life. Excessive cumulative deformation can lead to pavement cracking and uneven settlement of the subgrade. This study conducts a series of dynamic triaxial tests to analyze the effects of the number of cycles (N), effective confining pressure (sigma(c)), and dynamic stress amplitude (sigma(d)) on the axial cumulative strain (epsilon(d)) characteristics of solidified mud samples. Additionally, it investigates the evolution model of epsilon(d) of solidified mud and establishes a predictive model for this strain. In conjunction with the NMR tests, this research further investigates the effects of sigma(c) and sigma(d) on the pore distribution of solidified mud after loading. Ultimately, the correlation between microscopic pore structure indicators and epsilon(d) is elucidated. The results indicate that the epsilon(d) behavior of solidified mud under cyclic loading exhibits characteristics of plastic shakedown. Furthermore, the exponential hyperbolic function model more accurately characterizes the relationship between epsilon(d) of the samples and N. Before and after cyclic loading, the micropores of the samples accounted for over 95 % of the total pore volume, predominantly concentrated in the radius range of r < 0.3 mu m. A correlation exists between the average pore size of the sample and epsilon(d), which is primarily influenced by sigma(d) and sigma(c).