A realistic prediction of excess pore water pressure generation and the onset of liquefaction during earthquakes are crucial when performing effective seismic site response analysis. In the present research, the validation of two pore water pressure (PWP) models, namely energy-based GMP and strain-based VD models implemented in a one-dimensional site response analysis code, was conducted by comparing numerical predictions with highquality seismic centrifuge test measurements. A careful discussion on the selection of input soil parameters for numerical simulations was made with particular emphasis on the PWP model parameter calibration which was based on undrained stress-controlled/strain-controlled cyclic simple shear (CSS) tests carried out on the same sand used in the centrifuge test. The results of the study reveal that the energy-based model predicts at all depths peak pore water pressures and dissipation behaviour in a satisfactory way with respect to experimental measurements, whereas the strain-based model underestimates the PWP measurements at low depths. Further comparisons of the acceleration response spectra illustrate that both the strain- and energy-based models provide higher computed spectral accelerations near the ground surface compared with the recorded ones, whereas the agreement is reasonable at middle depth.

Seismic risk assessment of code-noncompliant reinforced concrete (RC) frames faces significant challenges due to structural heterogeneity and the complex interplay of site-specific hazard conditions. This study aims to introduce a novel framework that integrates three key concepts specifically targeting these challenges. Central to the methodology are fragility fuses, which employ a triplet of curves-lower bound, median, and upper bound-to rigorously quantify within-class variability in seismic performance, offering a more nuanced representation of code-noncompliant building behavior compared to conventional single-curve approaches. Complementing this, spectrum-consistent transformations dynamically adjust fragility curves to account for regional spectral shapes and soil categories, ensuring site-specific accuracy by reconciling hazard intensity with local geotechnical conditions. Further enhancing precision, the framework adopts a nonlinear hazard model that captures the curvature of hazard curves in log-log space, overcoming the oversimplifications of linear approximations and significantly improving risk estimates for rare, high-intensity events. Applied to four RC frame typologies (2-5 stories) with diverse geometries and material properties, the framework demonstrates a 15-40 % reduction in risk estimation errors through nonlinear hazard modeling, while spectrum-consistent adjustments show up to 30 % variability in exceedance probabilities across soil classes. Fragility fuses further highlight the impact of structural heterogeneity, with older, non-ductile frames exhibiting 25 % wider confidence intervals in performance. Finally, risk maps are presented for the four frame typologies, making use of non-linear hazard curves and spectrumconsistent fragility fuses accounting for both local effects and within-typology variability.

Lunar soil, as an in-situ resource, holds significant potential for constructing bases and habitats on the Moon. However, such constructions face challenges including limited mechanical strength and extreme temperature fluctuations ranging from -170 degrees C to +133 degrees C between lunar day and night. In this study, we developed a 3D-printed geopolymer derived from lunar regolith simulant with an optimized zig-zag structure, exhibiting exceptional mechanical performance and thermal stability. The designed structure achieved remarkable damage tolerance, with a compressive strength exceeding 12.6 MPa at similar to 80 vol% porosity and a fracture strain of 3.8 %. Finite element method (FEM) simulations revealed that the triangular frame and wavy interlayers enhanced both stiffness and toughness. Additionally, by incorporating strategically placed holes and extending the thermal diffusion path, we significantly improved the thermal insulation of the structure, achieving an ultralow thermal conductivity of 0.24 W/(m K). Furthermore, an iron-free geopolymer coating reduced overheating under sunlight by 51.5 degrees C, underscoring the material's potential for space applications.

The present paper sets out a comparative analysis of carbon emission and economic benefit of different performance gradients solid waste based solidification material (SSM). The macro properties of SSM were the focus of systematic study, with the aim of gaining deeper insight into the response of the SSM to conditions such as freeze-thaw cycles, seawater erosion, dry-wet cycles and dry shrinkage. In order to facilitate this study, a range of analytical techniques were employed, including scanning electron microscopy (SEM), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The findings indicate that, in comparison with cement, the carbon emissions of SSM (A1) are diminished by 77.7 %, amounting to 190 kg/t, the carbon-performance ratio (24.4 kg/ MPa), the cost-performance ratio (32.1RMB/MPa) and the carbon-cost ratio (0.76kg/RMB) are reduced by 86 %, 56 % and 68 % respectively. SSM demonstrated better performance in terms of freeze-thaw resistance, seawater erosion resistance and dry-wet resistance when compared to cement. The dry shrinkage value of SSM solidified soil was reduced by approximately 35 % at 40 days compared to cement solidified soil, due to compensatory shrinkage and a reduction in pores. In contrast to the relatively minor impact of seawater erosion and the moderate effects of the wet-dry cycle, freeze-thaw cycles have been shown to cause the most severe structural damage to the micro-structure of solidified soil. The conduction of durability tests resulted in increased porosity and the most probable aperture. The increase in pores and micro-structure leads to the attenuation of macroscopic mechanical properties of SSM solidified soil. The engineering application verified that with the content of SSM of 50 kg/m, 4.5 % and 3 %, the strength, bearing capacity and bending value of SSM modified soil were 1.9 MPa, 180 kPa and 158, respectively in deep mixing piles, shallow in-situ solidification, and roadbed modified soil field.

In situ resource utilization of lunar regolith provides a cost-effective way to construct the lunar base. The melting and solidifying of lunar soil, especially under the vacuum environment on the Moon, are the fundamentals to achieve this. In this paper, lunar regolith simulant was melted and solidified at different temperatures under a vacuum, and the solidified samples' morphology, structure, and mechanical properties were studied. The results indicated that the density, compressive strength, and Vickers hardness of the solidified samples increased with increasing melting temperature. Notably, the sample solidified at 1400 degrees C showed excellent nanohardness and thermal conductivity originating from the denser atomic structure. It was also observed that the melt migrated upward along the container wall under the vacuum and formed a coating layer on the substrate caused by the Marangoni effect. The above results proved the feasibility of employing the solidified lunar regolith as a primary building material for lunar base construction.

A novel iron-based phosphate cement (IPC), derived from iron-rich smelting slag (ISS), was developed as a sustainable and efficient binder for the stabilization/solidification of trivalent chromium (Cr3+). The mechanical properties, hydration behavior, microstructure, leaching toxicity, chromium chemical forms, and environmental safety of chromium-stabilized iron phosphate cement (CIPC) were thoroughly evaluated. The results showed that, with a mass ratio of ISS to ammonium dihydrogen phosphate (ADP) of 2.0, and even with the addition of 20 % chromium nitrate nonahydrate (CN), the compressive strength of CIPC reached 4.2 MPa after curing for 28 d. Furthermore, chromium leaching was well below 1 mg/L, significantly lower than the GB 5085.3-2007 standard limit of 15 mg/L, demonstrating the effective encapsulation of Cr3+ due to IPC's high early strength. In the IPC system, Cr3+ was primarily stabilized by forming CrPO4 and CrxFe1-x(OH)3 co-precipitates, which were further solidified through the physical encapsulation of IPC hydration products, such as (NH4)2Fe(PO3OH)2 center dot 4H2O, (NH4) (Mg,Ca)PO4 center dot H2O, and FePO4. This process resulted in a solidification efficiency of up to 99 %. BCR analysis confirmed that more than 98 % of the chromium in the CIPC remained in a stable residual form. Finally, the ecological risk index (PERT) was found to be 23.52, far below the safety threshold of 150, indicating the solidified material's long-term environmental safety. This study provides an innovative approach for the reutilization of ISS while effectively stabilizing/solidifying chromium.

This study presents a novel seismic control system, the Mega-Sub Controlled Structure System (MSCSS), to address vibration control challenges in tall and super-tall buildings under intense seismic excitations. The proposed hybrid VD-TFPB-controlled MSCSS integrates Triple Friction Pendulum Bearings (TFPBs) as base isolators with Viscous Dampers (VDs) between the mega frame and the vibration control substructure, enhancing damping and seismic performance. MSCSS without VD and MSCSS with VD models are established and verified using an existing benchmark. The hybrid VD-TFPB-controlled MSCSS is then developed to evaluate its vibration control response while considering soil-structure interaction (SSI). Numerical analyses with earthquake records demonstrate its superior performance compared to MSCSS without and with VD systems. Nonlinear dynamic analyses reveal that the hybrid system significantly improves vibration control. However, under SSI, increased structural flexibility leads to higher frame stress and more plastic hinges, particularly on soft soil, which amplifies vibrations. Despite these challenges, the hybrid VD-TFPB-controlled MSCSS effectively enhances seismic resilience, offering a robust solution for tall buildings.

A novel approach to enhance wellbore stability was put forth, based on the wellbore rock properties and instability mechanism of the hydrate reservoir, given the issue of wellbore instability when using water-based drilling fluids (WBDFs) in drilling operations, in weakly cemented muddy fine silt reservoirs of natural gas hydrates in the South China Sea. Three main strategies were used to increase the stability of reservoirs: enhancing the underwater connection between sandstone particles and clay minerals, preventing clay hydration from spreading and expanding, and strengthening the stability of hydration skeleton structure. An appropriate drilling fluid system was built with soil phase containing wellbore stabilizer. Sulfonic acid groups and electrostatic interaction were introduced based on the characteristics of underwater adhesion of mussels. Through the process of free radical polymerization, a zwitterionic polymer containing catechol groups named DAAT was prepared for application in natural gas hydrate reservoir drilling. DAAT is composed of tannic acid (TA), dimethyl diallyl chloride ammonium chloride (DMDAAC), 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and acrylamide (AM). Experimental results from mechanical property testing reveal an adhesion force of up to 4206 nN between SiO2 and 5 wt % DAAT, demonstrating its ability to bind quartz sand particles effectively. The compressive strength and cohesion of the cores treated with DAAT increased by 58.33 wt % and 53.26 wt %, respectively, at -10 degrees C, compared with pure ice particle cores. This demonstrates DAAT can significantly enhance the compressive strength and cohesion of the core. Furthermore, the adhesion force between DAAT and hydrate particles reaches up to 344.4 mN/m, significantly improving the structural stability between hydrate particles. It demonstrates excellent adhesive properties to hydrate particles. In addition to adsorbing clay minerals, rocks, and hydrate particles, DAAT also forms hydrogen bonds with argillaceous fine silt particles with its low temperature cohesiveness characteristic. As a result, it improves the cohesion between core particles, and enhances the adhesion between hydrates and rocks, thereby enhancing the stability of hydrate reservoirs. In summary, DAAT is characterized by a simple preparation process, cost-effectiveness, and environmental friendliness. It is an innovative and practical material for enhancing wellbore stability in WBDFs for natural gas hydrate exploration in the South China Sea.

In this study, ground granulated blast-furnace slag (GGBS) and fly ash (FA) were used as binders, while NaOH (NH) and Na2SiO3 (NS) served as alkali activators. Seawater (SW) was used instead of freshwater (FW) to develop a SW-GGBS-FA geopolymer for solidifying sandy soils. Geopolymer mortar specimens were tested for unconfined compressive strength (UCS) after being curing at room temperature. The results showed that the early strength of the seawater group specimens increased slowly less than that of the freshwater group specimens, while the late strength was 1.16 times higher than that of the freshwater group specimens. Factors including seawater salinity (SS), the GGBS/FA ratio, curing agent (CA) content, and the NH/ NS ratio were examined in this experiment. The results showed that the strength of the specimens was higher for SS of 1.2 %, G90:F10, CA content of 15 %, activator content was 15 %, and NH: NS of 50:50. The pore structure of the mortar specimens was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and computerized tomography (CT), revealing the mechanisms by which various factors influenced the microstructure. XRD indicated that SW-GGBS-FA geopolymer mortar newly produced Friedel salt and calcium silicate sulfate hydrate (C-S-S-H). The microstructures observed by CT and SEM showed that the pore radius of the seawater specimens was mainly less than 10 mu m, and the maximum crack length was 92.55 mu m. The pore radius of freshwater specimens was larger than that of seawater specimens, and the largest crack was 148.44 mu m, which confirmed that Friedel salt and C-S-S-H fill the pores and increase the UCS of the specimens.

Determining the optimal damping value of the isolation system in tall structures is challenging as it requires parametric studies and time-consuming nonlinear time-history analyses. Consequently, the influence of different parameters, such as displacement limitation, on the optimal damping of isolators in tall structures remains unclear. This study aims to investigate the optimal damping of isolators in tall structures under two scenarios: a) changing the displacement capacity of the isolators in proportion to the increase of damping (variable gap); b) maintaining a constant displacement capacity of the isolators as the damping increases (constant gap). The study also explores the influence of two additional parameters on the optimal damping of the isolation system, namely the ratio of isolator to superstructure period (TM/TS) and the soil type. The optimal design procedure is illustrated with reference to a case-study 14-story isolated steel structure with an ordinary concentrically braced frames (OCBF) system, isolated with the triple friction pendulum isolator (TFPI) system. The modified endurance time (MET) method is utilized to analyze the seismic response of the case-study structure under increasing levels of earthquake hazard. The analysis reveals that increasing damping in both constant and variable gap modes can effectively reduce the damage level of the structure. However, the effectiveness of increasing damping is limited and influenced by factors such as soil softness and the TM/TS ratio. The optimal damping values are determined based on the desired performance levels for both structural and nonstructural acceleration-sensitive components.