This study investigates the strength development of cement-stabilized marine clay, which is influenced by a complex interplay of microstructural factors. To optimize its performance for coastal and offshore engineering, we explored the relationship between microstructure and unconfined compressive strength (UCS). Using Scanning Electron Microscopy (SEM) and the Pore/Crack Analysis System (PCAS), we analyzed samples with varying cement contents (10%, 15%, and 20%) and curing times (3, 7, 14, and 28 days). Key microstructural parameters, including porosity, particle shape, size, and arrangement, were quantified and correlated with UCS results. A novel comprehensive micro-parameter was introduced to encapsulate the combined effects of these factors, revealing an exponential relationship with strength development. The findings provide a quantitative framework for predicting the performance of cement-stabilized marine clay, contributing to more efficient solutions in geotechnical engineering.

In this study, based on the background of massive freezing engineering in coastal strata, the thermal physical parameters and some freezing laws of soil were obtained through soil thermal physical tests and frozen soil frost heaving tests. When the freezing temperatures were −5°C, −10°C, −15°C, and −20°C, the frost heaving rates of the soil were 0.53%, 0.95%, 1.28%, and 1.41%, and the frost heaving forces of the soil were 0.37 MPa, 0.46 MPa, 0.59 MPa, and 0.74 MPa, respectively. In the range of test conditions, the frost heaving rate and the frost heaving force of the soil increased with the decrease of the freezing temperature, and the relationship was roughly linear with the temperature. The entire cooling process could be roughly divided into three stages: active freezing stage, attenuation cooling stage, and stability stage. The range of the frozen soil expansion did not increase linearly with the decrease of the freezing temperature, and there was a limit radius for the frozen soil expansion. A three‐dimensional finite element model was established to simulate the temperature field and frost heaving of the soil under the on‐site working conditions. The entire frost heaving process could be roughly divided into two stages. The calculated temperature values and the frost heaving force values were compared with the on‐site measured values, and the results verified that the numerical calculation could accurately reflect the temperature field and frost heaving law of the formation.

This study reveals the thermal control mechanism of a ventilated–closed block layer composite embankment structure by analyzing the heat transfer and temperature change based on the measured data of the high-grade highway experimental engineering in the Beiluhe area of the Qinghai–Tibet Plateau. During the cold season, natural convection occurred in the block layer when the upper boundary temperature was approximately 2 °C lower than that of the bottom boundary. In addition, heat from the foundation was transferred upwards through the block layer via heat convection. During the warm season, air inside the block layer was almost static, and external heat was transferred downwards through the block layer via heat conduction. The equivalent thermal conductivity of the block layer in the cold season was approximately 17.4 times that of the warm season, and heat release through the block layer was 9.65 times that of heat absorption, exhibiting a thermal semiconductor effect. The results show that the frozen soil foundation was in net exothermic state, the permafrost table continuously rose, and the mean annual soil temperature continuously decreased above 14 m depth. This research can contribute to thermal control technology development and construction scheme selection of expressway in permafrost regions.

The strength of cement-treated soil (CTS) is influenced by a range of complex factors. Investigating the microstructure of cement-treated soil provides a fundamental understanding of its strength evolution. This study explores the micro-mechanism of strength in cement-treated soil through qualitative and quantitative analyses. Unconfined compressive strength (UCS) tests were conducted on two types of cement-treated soils with different curing ages. Microstructural images were obtained via Scanning Electron Microscopy (SEM), from which micro-parameters—including image porosity ($n_s$), mean shape factor ($F$), particle grading entropy ($G_e$), and directional probability entropy ($H_m$)—were obtained. Finally, the Grey Relation Analysis (GRA) method was employed to evaluate the relative importance of these micro-parameters in influencing strength. And the micro-mechanism of strength was discussed. Results show that these variations of cement-treated soil strength are primarily governed by porosity, particle shape, size, and arrangement. GRA results indicate that particle grading entropy ($G_e$) has the greatest impact on CTS strength, followed by image porosity ($n_s$). In contrast, mean shape factor ($F$) and directional probability entropy ($H_m$) have relatively lower impacts. The order of influence is $G_e>n_s>F \mathrm{a}\mathrm{n}\mathrm{d} H_m$, suggesting that changing particle grading entropy ($G_e$) is recommended to achieve higher CTS strength more efficiently. Finally, a polynomial relation between $G_e$ and strength is proposed and the sensitivity analysis indicates that the best value of $G_e$ for Hangzhou CTS is 0.3125 and for Taizhou CTS is 0.5. The corresponding UCSs are 56.96 kPa and 425.8704 kPa, respectively. These findings contribute to optimizing the strength of cement-treated soils and provide insights into the micro-mechanisms underlying macro-scale material properties.