To analyze the progressive failure of structural loess slopes due to changes in humidity and loading, this study analyzes the degrees of influence of these changes on slope failure and their relationships with various structural parameters. According to the analysis, the shear failure of the soil gradually develops with the change of the water content. When the water content reaches a 17%, with the development of shear deformation, the shear zone is formed and finally penetrates the soil body. With the increase of the water content, the total displacement of the slope body gradually develops. When the water content reaches 17%, the total displacement of the slope body changes suddenly. This mutation is consistent with the formation of the shear zone. The sudden change of displacement indicates the penetration of the shear zone and the damage and slippage of the slope. With the increase of the soil moisture of the slope, the strain localization phenomenon occurs, the development of strain localization and shear bands increases, the structural damage increases, and the quantitative structural parameters decrease. The quantitative parameters can therefore be used to evaluate the feasibility and rationality of the progressive failure process of homogeneous structural loess slopes.

Low-carbon and highly printable cementitious materials are crucial for the practical application of extrusion-based three-dimensional concrete printing (3DCP). This study develops and optimizes a one-part alkali-activated concrete suitable for 3D printing through an integrated experimental and evaluation approach. An orthogonal experimental design was employed to investigate the effects of precursor ratio (ground granulated blast-furnace slag, GGBFS, to fly ash, FA), water-to-binder ratio, activator dosage, and retarder content on fresh-state properties, rheological behavior, setting characteristics, and mechanical performance. The optimal mixture was determined using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) multi-criteria decision method. The mixtures exhibited suitable rheology, with a yield stress of 90–141 Pa and a plastic viscosity of 3.5–7.2 Pa·s, a setting time of 40–96 min, and mechanical performance with compressive and flexural strengths of 29–71 MPa and 4.2–6.9 MPa, respectively. The optimal mixture provided a 95-min printing open time and an acceptable pumping pressure of 1.77 MPa, while full-scale tests confirmed stable extrusion and good print quality. Furthermore, within the defined cradle-to-gate, materials-stage boundary and the adopted inventory factors, the optimized alkali-activated mixture exhibited an embodied CO₂ emission of 0.113 kg CO₂/L, which is approximately 61% lower than that of the reference cement-based printable mixture. The proposed approach provides a systematic framework for designing low-carbon, high-performance one-part alkali-activated materials for extrusion-based 3D concrete printing applications.

With the rapid expansion of underground rail transit construction in China, the high carbon emissions associated with subway tunnels and stations have become an increasing concern. This study systematically examines the carbon emissions of prefabricated concrete–filled steel pipe columns (PCSPCs) during the construction phase of a Beijing subway station built via the pile beam arch (PBA) method, applying the life cycle assessment (LCA) methodology as a case study. An analytical framework for the synergistic optimization of carbon emissions and costs was developed. By systematically adjusting key design parameters—such as the column diameter, wall thickness, and concrete strength—it was possible to minimize both carbon emissions and project costs while meeting the ultimate load-bearing capacity requirements. The results indicate that the production phase of PCSPCs accounts for as much as 98.845% of total carbon emissions, with labor, materials, and machinery contributing 10.342%, 88.724%, and 0.934%, respectively. A sensitivity analysis revealed that steel plates have the greatest impact on carbon emissions, followed by steel reinforcement, whereas concrete and cement exhibit relatively lower sensitivities. The ultimate load-bearing capacity of PCSPCs increases with larger column diameters, thicker walls, and higher concrete strength grades, with the relationships displaying a nonlinear trend. The damage modes and performance of PCSPCs under different design parameters were further verified through finite element analysis. On the basis of the optimization algorithm used to adjust the design parameters, the carbon emissions and costs of the PCSPCs were reduced by 10.32% and 21.55%, respectively, while still meeting the load-bearing capacity requirements.

Understanding the mechanical behavior of undisturbed loess under different hydraulic paths (wetting followed by loading(W-L) and loading followed by wetting(L-W)) is critical for geotechnical engineering in loess regions. This study investigates the macro–micro deformation characteristics of undisturbed loess using improved triaxial tests, scanning electron microscopy (SEM), Grey Relational Analysis, and Pearson correlation analysis. This combined approach quantitatively links macroscopic mechanical responses with microstructural evolution. Grey Relational Analysis and Pearson correlation analysis were used to quantify the coupling between macroscopic mechanical properties and microscopic pore parameters. The results reveal distinct deformation behaviors: the L-W path induces significantly larger deviatoric strain than the W-L path, with strain increasing notably as deviatoric stress rises. Microstructurally,both paths promote the transformation of large and medium pores into small and micropores with increasing stress, accompanied by enhanced pore orientation and reduced morphological complexity. The L-W path intensifies these effects due to stress-induced particle rearrangement followed by wetting-induced effective stress redistribution. Grey Relational Analysis and Pearson correlation analysis confirms that pore orientation (distribution entropy) is the most sensitive to hydraulic paths, followed by pore roundness and abundance, while pore circumference and length exhibit minimal correlation. These findings highlight the critical role of the loading-wetting sequence and provide a quantitative macro–micro framework for assessing moisture-induced deformation risks in loess-region infrastructure.

In this study, the dispersion behavior of piezoelectric sandwich nanoplates is examined using the nonlocal strain gradient theory (NSGT). Specifically, the evolution law of frequency and phase velocity (PV) with the wave number (WN) is investigated. The sandwich nanoplate has a metallic central layer and a piezoelectric surface layer, and the nanoplate is deposited on top of a viscoelastic substrate. The viscoelastic substrate is modeled using a three-parameter viscoelastic model. The surface effects (SEs) of the piezoelectric layer, including its elastic parameters, piezoelectric parameters, dielectric parameters, and residual stresses, on the dispersion characteristics are systematically considered. The equations of motion are determined by Hamilton’s principle and NSGT. Furthermore, the scale effects, SEs, and viscoelastic effects on the dispersion properties are comprehensively explored. The results reveal that the contribution of scale and viscoelastic effects to the dispersion properties is strongly dependent on the WN, and the impact of SEs on the frequency is inseparable from the thickness of the piezoelectric sandwich nanoplates.