The understanding of the mechanical properties of sensitive marine clay subgrade stabilized with cement is vital for the safe, economical, and durable design of road structures. As the curing temperature affects the cement hydration progress, it is necessary to investigate the influence of the temperature on the evolution of the mechanical properties of cement-reinforced marine clay in road construction. A column testing and relevant monitoring program were performed to study the effect of various curing temperatures (2 °C, 22 °C, and 40 °C) on the mechanical properties’ development of cement-reinforced clay within 28 days. After these cement clay samples were cured for a specific time (1, 3, 7, and 28 days), they were subjected to two mechanical tests (i.e., California Bearing Ratio (CBR) test and uniaxial compressive strength (UCS) test). The findings reveal that a higher curing temperature accelerates cement hydration and self-desiccation. Consequently, the UCS and CBR values increase with curing temperature and the strength might vary by more times, especially for early age (≤7 days) samples. The results of this study contribute to a deeper understanding of the influence of temperature on the mechanical properties of the cement-reinforced clay and thus provide practical guidance with regards to road construction in the field.

Understanding the spatial distribution patterns of soil organic carbon components in Ecological Vegetative Slopes (EVS) is crucial for optimizing restoration strategies, enhancing soil carbon sequestration capacity, and scientifically evaluating rehabilitation effectiveness. It is an important pathway for promoting sustainable development. This study investigated the effects of slope gradient, slope position, vegetation type, and cement content on the spatial distribution characteristics of soil total organic carbon (TOC) and its components (readily oxidizable organic carbon (ROC) and dissolved organic carbon (DOC)) through slope model experiments and laboratory analyses. The key findings revealed that (1) TOC, ROC, and DOC concentrations decreased with increasing slope gradient and upper slope positions, with steeper slopes amplifying positional effects and exhibiting surface-layer accumulation characteristics. (2) The highest TOC, ROC, and DOC content was achieved in the mixed planting slope with Bermudagrass and Magnolia under a substrate thickness of 3 cm and 3% cement content. Lastly, (3) soil pH increased with the slope gradient and upper positions, showing systematic variations across vegetation types and cement contents. Comparative analysis demonstrated that optimizing vegetation composition and cement dosage effectively enhanced SOC accumulation, while slope gradient and position dominated the spatial heterogeneity of carbon distribution. These results provide theoretical and practical guidance for the precision management of slope ecological restoration. These findings provide robust data support for the ecological sustainability of engineering slope restoration and the enhancement of soil carbon storage.

Rain is an important factor influencing the instability of ecological slopes. There is little research on the inherent quantitative influence of substrate properties on slope runoff and water infiltration to support accurate ecological slope protection design. In this paper, the influence of substrate characteristics on slope runoff and water infiltration is quantitatively analyzed by constructing large physical models with different substrate characteristics for artificial rainfall simulations. The experimental results showed that the cumulative runoff volume and slope runoff rate were positively correlated with the cement content and substrate thickness in a 4 h, 60 mm/h artificially simulated rainfall. Specifically, the cumulative runoff volume increased by 2.06% for every 1% increase in cement content, and the cumulative runoff volume increased by 3.93% for every 1 cm increase in substrate thickness. The substrate inhibited the advance of the wetting front, and at different slope locations, the transport rate of the wetting front exhibited a mid-slope > upslope. Moreover, the transport rate of the wetting front showed a non-linear relationship with time as a power function V = a·t^b, with the cement content showing a linear relationship with parameters a and b, and the substrate thickness showing a non-linear relationship with parameters a and b. The cumulative infiltration and infiltration rate were negatively correlated with cement content and substrate thickness, as shown by a 2.2% decrease in cumulative infiltration for every 1% increase in cement content and a 4.73% decrease in cumulative infiltration for every 1 cm increase in substrate thickness.

Due to Paleo-clay’s unique properties and widespread distribution throughout China, it is essential in geotechnical engineering. Rainfall frequently causes the deformation of Paleo-clay slopes, making slope instability prediction crucial for disaster prevention. This study explored Paleo-clay’s strength degradation and slope stability under soaking and wet–dry cycles. Using Mohr–Coulomb failure envelopes from experiments, curve fitting was used to find the patterns of Paleo-clay strength degradation. Finite element simulations and the strength discounting method were used to analyze the stability and deformation of Paleo-clay slopes. The results indicate that wet–dry cycles impact them more than soaking. Paleo-clay’s cohesion decreases exponentially as the number of wet–dry cycles and soaking times rise, but the internal friction angle changes very little. After 10 wet–dry cycles and 24 days of soaking, iron-bearing clay’s cohesion decreased to 17% and 44% and reticular clay’s to 32% and 48%. Based on the study area characteristics, three slope types were constructed. Their stability exhibited exponential decay. Under soaking, stability remained above 1.4; under wet–dry cycles, type I and II stability fell below 1.0, leading to deformation and failure. All types showed traction landslides with sliding zones transitioning from deep to shallow. Practical engineering should focus on the shallow failures of Paleo-clay slopes.

The stabilization of soft, organic-rich soils with cement is often hindered by retarded hydration and poor long-term performance under cyclic loads. While nano-silica or sand are known modifiers, their individual efficacy in high-organic environments remains limited, and a systematic comparison of their composite effect across different soil types is lacking. This study investigates the synergistic enhancement of cement-stabilized soils using a combined nano-SiO₂ and sand composite, comparing its effectiveness in high-organic soft soil and low-organic clay. Laboratory tests, including unconfined compressive strength (UCS), cyclic loading, scanning electron microscopy (SEM), and X-ray diffraction (XRD), were conducted. Results showed a stark contrast in 28-day UCS between unmodified soft soil cement (0.13 MPa) and clay cement (1.04 MPa). The optimal composite of 3.5% nano-SiO₂ and 40% sand increased the 28-day UCS to 1.39 MPa for soft soil (a 969% improvement) and 5.51 MPa for clay (a 430% improvement), respectively. Notably, under a cyclic stress ratio (CSR) of 0.7~0.8, unmodified specimens failed after fewer than 120 load cycles, whereas the composite-modified soils withstood 20,000 cycles without failure, demonstrating exceptional fatigue resistance independent of static strength gain. Microstructural analysis revealed that the composite effectively promoted the formation of cementitious hydration products, counteracting the inhibitory effect of organic matter. This research demonstrates that the nano-silica sand composite provides a superior and more broadly applicable improvement for cement-stabilized soils across the tested organic content range (3.3–7.7% LOI) compared to single-additive approaches, significantly enhancing both mechanical strength and long-term durability.

A large amount of construction and demolition waste (CDW) is generated during the construction of projects. In this paper, polyurethane foam adhesive (PFA) was used to improve the mechanical properties of CDW. The large-scale direct shear tests, California bearing ratio (CBR) tests and Scanning electron microscope (SEM) tests were carried out to study the variation regularities of mechanical properties of treated CDW during the laboratory tests. The test results show that the shear strength of CDW increases with the increase of PFA content, vertical pressure and the shear rate. However, the increase of vertical pressure on the shear strength of CDW is smaller than that of PFA, and the improvement of the shear rate is relatively small. The California bearing ratio (CBR) test also proves that PFA can effectively improve the bearing capacity of CDW and reduce the loss of CBR caused by the 4-day soaking. Scanning Electron Microscope (SEM) finds that polyurethane wraps multiple particles and enhances the internal connection, which results in the cohesion between the particles being greatly increased. The study presented in this paper will better assess the shear resistance of improved CDW with PFA as a substitute for pavement base materials in practical engineering applications.