This article deals with the effect of configuration on the load-settlement performance of column-type sub-structural elements with varying lengths, which have been widely used in geotechnical applications to provide cost-effective foundation solutions in weak soil areas. The numerical analysis results show that resting a footing/raft over 5 × 5 cushioned varying-length rigid inclusions (RIs) with an A-shape arrangement pattern (Configuration I) reduces raft settlement by about 12% compared with uniform short RIs and by 4.3% compared with uniform long RIs under the same distributed load. Furthermore, synergistic interactions between the cushion layer, soil and RIs in variable-length RI configurations, particularly those that concentrate longer RIs centrally, outperform uniform groups by enhancing the composite modulus and optimising load transfer to deeper strata. In addition, the farther the RI is from the group centre, the greater the proportion of the applied load it bears. Finally, a simplified load transfer analysis method is proposed using hyperbolic load transfer functions by employing the concepts of traditional pile group analysis, which approximately considers the cushion-RI-soil interaction and the mutual interactive effects of neighbouring varying length RIs in the group. The proposed method produces satisfactory results.

Landslide-generated impulse waves (LGIWs) are among the most catastrophic natural hazards, particularly in reservoir areas where they often cause devastating consequences. This study investigates the impacts of LGIWs through a combined experimental and numerical approach. A large-scale three-dimensional (3D) prototype physical model of the Meilishi (MLS) landslide in China’s Gushui (GS) Reservoir is constructed at a scale of 1:150. Based on the physical experiment results, a 3D numerical model that couples the granular flow model and renormalisation group (RNG) turbulence model in FLOW-3D is established to analyse the generation and propagation of LGIWs in reservoirs. The numerical simulations show strong agreement with experimental data under identical conditions. Simulated wave amplitudes closely match the time-series data from the physical model, with relative errors below 15% in the wave generation and propagation areas and under 5% near the dam area. These results demonstrate the numerical model’s capability to accurately reproduce the complex nonlinear processes of wave generation and propagation induced by subaerial landslides, particularly for large-scale, long-distance LGIW propagation analysis.

In this study, Recycled Concrete Fine Aggregate (RCFA) derived from non-demolished, laboratory-cured concrete processed through a regulated crushing procedure was used to investigate the stabilisation of compacted clayey soils. Owing to consistent composition, reduced impurities, and enhanced material uniformity, it was aimed to develop a systematic understanding of the mechanisms governing RCFA–clay interactions to support more predictable and sustainable soil improvement strategies in geotechnical engineering. In particular, the compaction characteristics showed significant improvement, which contrasts with trends typically reported in the literature. While an increase in unconfined compressive strength (UCS) was also observed, it was not as pronounced as that reported in studies utilising RCFA derived from construction and demolition (C&D) waste. The behavioural differences and performance outcomes were thoroughly examined experimentally through compaction tests and UCS tests, as well as microstructural investigations using the Scanning Electron Microscopy (SEM) technique. Additionally, machine learning (ML) sensitivity analysis methods, K-means clustering, and Ordinal Logistic Regression (OLR), were applied to analyse the influence of curing duration, plasticity index (Ip ), RCFA content, and moisture content (w) on UCS. These models demonstrated high predictive accuracy and revealed key insights into factors controlling soil performance. The study offers valuable insights for future research, opening new considerations in soil improvement on how the origin and treatment of recycled aggregates can influence their effectiveness.

This study investigates the effectiveness of nano-pozzolanic materials – nano-fly ash (CNF) and nano-cement (CNC) – in improving the corrosion resistance and bond performance of reinforced concrete. Concrete mixes were prepared by partially replacing cement with CNF (5–20%) and CNC (5–35%), alongside a control mix (OC) without nanomaterials. Specimens were subjected to accelerated chloride-induced corrosion using an impressed current in a 5% NaCl solution. Durability performance was assessed through half-cell potential, water permeability and rapid chloride penetration tests (RCPT), while compressive strength was measured before and after corrosion exposure. Bond-slip behaviour was evaluated through pull-out tests, and reinforcement degradation was analysed by measuring mass loss and residual tensile strength. Results indicated that mixes incorporating 15% CNF and 30% CNC achieved the highest performance. These mixes exhibited compressive strength gains of 37.6% and 32.8%, respectively, over the control mix. Strength loss under chloride exposure was limited to 14.6% (CNF15) and 15.7% (CNC30), compared to 52.8% in the control. Ductility indices and energy absorption capacities were also significantly enhanced in nano-modified specimens. The study confirms that nano-pozzolanic additives can enhance the mechanical performance and durability of reinforced concrete, offering a promising solution for sustainable construction in aggressive environments.

The flow behaviour of Ultra-High Performance Concrete (UHPC) plays a critical role in determining its workability at the fresh stage, as well as its mechanical performance and durability after hardening. A three-dimensional computational model is established to simulate UHPC flow, in which the Herschel–Bulkley constitutive law is adopted to represent the nonlinear fresh state rheology of UHPC. The model is validated against L-box experiments, yielding an average relative error not exceeding 7.2%. Building upon this validated framework, this study investigates mould filling evolution in a large precast capping beam shell, with particular attention to the effects of different boundary conditions and related mechanisms. The obtained results indicate a transition in the flow regime from an initial shear-dominated phase to a confined mode governed by hydrostatic pressure accumulation and yield stress resistance. Moreover, both the number of filling locations and the total filling area exhibit strong positive correlations with filling efficiency. From a rheological perspective, the findings elucidate the dynamic mechanisms that govern UHPC flow in confined environments and provide a theoretical foundation for optimising filling processes in large precast UHPC components.

The dynamic instability of fly ash deposits under cyclic loading poses a major challenge in landfill development, land reclamation and seismic ground improvement. Although biopolymers are identified as sustainable stabilisers, their effectiveness in improving the cyclic stability of fly ash remains unexplored. This study examines the efficacy of xanthan gum, a microbial biopolymer, in improving the dynamic behaviour of fly ash. Strain-controlled cyclic triaxial tests were conducted on untreated and 28-day cured xanthan gum-treated fly ash under varying confining pressures (0.05–0.20 MPa), loading frequencies (0.50–1.25 Hz) and overconsolidation ratios (1–4). The rapid shear modulus degradation and significant pore pressure generation in the untreated fly ash indicate early liquefaction onset. In contrast, treated samples showed marked improvements, with shear modulus and damping ratio increasing by 257% and 277% under higher confinement, 443% and 154% at low frequencies and 297% and 515% at high overconsolidation ratios, respectively. The treated samples maintained pore pressure ratios below unity, indicating enhanced liquefaction resistance. Stress path analysis revealed a stable mean effective stress and restricted strain accumulation, whereas microstructural observations confirmed pore filling and cation-mediated interparticle bridging. These findings demonstrate the potential of xanthan gum to transform fly ash into a sustainable material for seismic ground improvement.

Hempcrete is a sustainable bio-composite known for its excellent thermal insulation. This study explores the effects of hemp hurd size and content on the mechanical and thermal performance of hempcrete to determine the optimal mix parameters. Four hemp hurd types were examined: HS1 (coarse, long flaky hurds from Canadian harvest), HS2 (medium flaky hurds from Canadian harvest), HS3 (fine hurds from Canadian harvest) and HS4 (well-graded short hurds from a French harvest). Five hemp contents (20, 40, 50, 67 and 100 wt.% of binder) were tested. HS4 hurds (3–10 mm) provided the best grading, reducing porosity and enhancing strength, achieving compressive strengths of 1.33 MPa (dry) and 0.77 MPa (wet). Coarser hurds (HS1, HS2) increased porosity, while finer hurds (HS3) raised binder demand and interfacial failure risk. Hempcrete with HS4 exhibited the highest thermal conductivity (0.131 W/(m∙K)), as fine particles hindered heat diffusion while coarse ones increased void content. Increasing hemp content decreased density, strength, conductivity and heat capacity, with thermal diffusivity governed by the balance between conductivity and capacity. Thermal modelling indicated energy losses of 27% at 24 h for 20 wt.% hemp and 14% for 100 wt.%. Overall, well-graded hurds (HS4) with optimised hemp content achieved the optimal strength–insulation balance.

As a critical factor governing the strength and deformation behaviours of granular materials, dilatancy characteristics inherently exhibit intricate complexity arising from stochastic particle arrangements and dynamic motion patterns. This article introduces a stress-dilatancy relationship considering the variation of contact number within granular assemblies from the perspective of micromechanics. At microscopic scale, average contact force and displacement expressions are derived using the true stress tensor. And then the variation of contact number is introduced to further optimise the description of the energy dissipation behaviours of granular materials. Following that, the stress dilatancy relationship for granular materials considering of the evolution of fabric anisotropy are established through macro-micro energy conservation. The stress-dilatancy relationship can well describe the phenomenon that the stress ratio for dense sand at the phase transition point is inconsistent with the critical stress ratio. Compared with the reults of experiments obtained from Ottawa sand, the established stress-dilatancy relationship can better describe macroscopic deformation response than the classical flow law such as the Cam-Clay model and Rowe dilatancy model. Moreover, under true triaxial stress paths and different initial anisotropies, the mechanical responses of the proposed stress-dilatancy relationship are consistent with the results of discrete element method simulation experiments.

This study experimentally and theoretically investigated the behaviour of concrete beams reinforced with different glass fibre-reinforced polymer (GFRP)–steel combinations without/with fire exposure. Experiments were performed on 12 concrete beams reinforced with 4 GFRP-steel combinations, which are represented by the ratios (ρf/fs ) of GFRP area to total reinforcement area. The test results indicated that the increase in ρf/fs and fire duration shifted the flexural failure of the tested beams to shear failure. At room temperature, the ultimate load of concrete beams reinforced with both GFRP and steel bars increased by approximately 20%, while that of concrete beams reinforced with only GFRP increased by 11.8% compared with beams reinforced with only steel. Exposed to 30-min and 60-min fires, the ultimate loads of concrete beams with ρf/fs =0.0–1.0 decreased by 13.3%–77.3% and 39.3%–96.0% compared with those of their counterpart, respectively. The elastic stiffness was significantly affected by both ρf/fs ratio and fire duration. Concrete beams reinforced with only GFRP had 67.4% lower stiffness than those reinforced with only steel. 30-min and 60-min fires significantly decreased the elastic stiffness by 44.6%–54.3% and 71.8%–76.0% compared with their counterpart, respectively. Finally, a method for estimating the load-carrying capacity of postfire GFRP-steel reinforced concrete (RC) beams was proposed.

The concrete production is under increasing pressure to reduce environmental impact. This study evaluates the durability and microstructure of high-strength concrete (HSC) incorporating metakaolin (MK), palm oil fuel ash (POFA), with coal bottom ash (CBA) as fine aggregate. The strength, water absorption, and resistance of modified HSC to sodium chloride were assessed. The findings indicated that a combined 10-15% MK% and 20% POFA achieved an improvement in the concrete strength. The optimal mixture, containing MK and POFA with CBA as fine aggregate, consists of 15% MK, 20% POFA, and 10% CBA. A power relationship was established between the compressive strength and split tensile strength of MK-based HSC, MK-POFA-based HSC, and MK-POFA-based HSC with CBA as fine aggregate. The established relationships of modified HSC indicate that the Neville equation underestimates the experimental strength, while the ACI 363 and ACI 318 equations overestimate it. Using 10–15% MK and 20–30% POFA reduced the water absorption to 1.28–1.54%. However, incorporating 10–20% CBA into the ternary blend slightly increased it to 1.64–2.01%. The mixture blended with 15% MK and 20% POFA reduced the drop in compressive strength, tensile strength, and ultrasonic pulse velocity (UPV) by 3.8%, 1.2%, and 4.7%, respectively, after 300 days of exposure to 5% NaCl. The incorporation of 10% CBA into the ternary blend slightly decreased the resistance to chlorides. The scanning electron microscopy (SEM) illustrated less migration and crystallisation of chloride ions through concrete. Furthermore, X-ray diffraction (XRD) analysis showed that the incorporation of MK and POFA resulted in a reduction of Ca(OH)2, thereby enhancing the concrete durability.