Search Results (208)

The elastoplastic behaviour and failure of unreinforced masonry structures under biaxial loading are critically governed by the mechanical response of brick–mortar contact interfaces. Detailed finite element micromodelling explicitly resolves these elements, offering rigorous numerical representation; however, practical implementation requires the determination of contact stiffness parameters, for which no established experimentally calibrated expressions exist. This study presents an experimental-numerical calibration methodology integrating experimental characterisation of constituent materials and small-scale masonry specimens with numerical validation, using a concrete damaged plasticity model for quasi-brittle materials and traction-separation laws for interfaces, applied to a specific ceramic masonry system. The proposed methodology provides a practical and reproducible basis for experimental calibration of the contact stiffness parameters required in the detailed micromodelling of brick–mortar interfaces. Numerical simulations reproduce experimental behaviour, with peak load predictions within ±6% for normal and ±1% for shear loading. Detailed micromodelling reveals that normal stresses develop at interfaces even under nominally pure shear, evidencing coupled normal-tangential behaviour, the key role of normal adhesive contact strength, and the justification for the cohesive–frictional interface characterisation. Full article

Wet–dry cycling triggers progressive degradation of the physical and mechanical properties of silt soils, severely compromising the long-term serviceability and structural safety of silt subgrade infrastructure. This study proposes a sustainable nano-hydrophobic material (NSHM) modification strategy to enhance the W-D cycle durability of silt. A multi-scale experimental program integrating wettability characterization, mechanical testing and microstructural analysis was conducted to elucidate the modification mechanism, performance attenuation law and microstructural evolution of NSHM-treated silt under cyclic wetting–drying. Results reveal that NSHM effectively imparts robust water repellency to silt, with a distinct dosage threshold effect and a synergistic enhancement from soil relative density. Silt modified with 0.5% NSHM maintains stable hydrophobicity after 5 W-D cycles, with a contact angle reduction of less than 1.3%. Compared with untreated specimens, the 0.5% NSHM-treated silt exhibits only 3%–8% unconfined compressive strength loss, 20%–30% higher cohesion and 8%–20% higher internal friction angle after 5 cycles. The superior durability originates from the synergistic effect of chemical anchoring and physical coating, which firmly immobilizes the hydrophobic network on particle surfaces and overcomes the inherent drawbacks of easy leaching and poor durability in conventional modification methods. This work provides a sustainable soil improvement strategy for W-D-prone regions, with significant engineering value for mitigating performance degradation of geotechnical infrastructure. Full article

This paper presents a method of using recycled tyre-derived grids (RTDG) as reinforcement materials for mechanical stabilised weathered sand embankment. To demonstrate the effectiveness of the RTDG-reinforced weathered sand on shear behaviour, large-scale triaxial tests were conducted under different confining pressures and reinforcement layers. The test results indicate: (1) RTDG reinforcement significantly alters the shear failure mode of weathered sand, transitioning it from shear failure to bulging failure. (2) RTDG reinforcement enhances the ultimate deviatoric stress of specimens by 20–30%, transforming the stress–strain response from strain softening to strain hardening. (3) RTDG reinforcement causes apparent cohesion to increase at an approximate linear rate of 37.2% per reinforcement layer, whereas the internal friction angle exhibits only a gradual increase. (4) The coupled effect of RTDG reinforcement and confining pressure alter volumetric behaviour from shear contraction–dilation patterns to solely shear contraction. It also reduces maximum dilation strain by about 50% and the dilation angle by 23%. (5) Two shear strength prediction models based on confinement enhancement (CEB) and interface friction (IFB) were proposed. Comparative analysis shows that, within the present dataset, the IFB model exhibits lower prediction error and a more stable error distribution than the CEB model, with a WRAI value of 0.033. Accordingly, the IFB model provides an effective prediction approach for estimating the shear strength of RTDG-reinforced weathered sand within the investigated test range, and the corresponding prediction results may serve as a preliminary reference for the engineering evaluation of RTDG-reinforced weathered sand. Full article

This study evaluates the shear strength and geomechanical behavior of the soil–concrete interface in carbonate sands from the coast of Ceará, with particular relevance to offshore wind turbine foundations. Three sands with different calcium carbonate (CaCO₃) contents, namely, 10.6%, 22.0% and 30.0%, were tested under applied normal stresses of 50, 100 and 200 kPa. Conventional direct shear tests were carried out to determine soil–soil shear behavior, whereas controlled-interface tests were performed using cementitious specimens with smooth and rough surfaces. The soil–soil tests indicated effective internal friction angles (φ′) between 35° and 38°, with no cohesion. No direct correlation was observed between shear strength and CaCO₃ content. Instead, the results indicate that particle size distribution, particularly the proportion of finer fractions, exerted the main control on mechanical behavior. Within the three materials tested, no monotonic trend between CaCO₃ content and shear strength was identified, a finding that should be confirmed with a larger sample set. At the soil–concrete interface, shear stress mobilization depended on surface roughness, with the rough surface mobilizing higher shear stresses than the smooth surface. The ratio between the interface friction angle and the soil effective internal friction angle (δ/φ′) ranged from 0.963 to 0.994 for rough surfaces and from 0.859 to 0.951 for smooth surfaces. These findings show the need for site-specific characterization of carbonate sands and for explicit consideration of interface conditions in offshore foundation design, thereby reducing unnecessary structural oversizing. Full article

Alkali-activated slag–loess cemented backfill materials are subjected to coupled confining pressure and curing temperature in open-pit end-slope backfill mining. This study investigates their mechanical properties and microscopic mechanisms under four confining pressures (0, 2, 4, and 6 MPa) and four curing temperatures (5, 20, 35, and 50 °C) at a curing age of 7 days. Uniaxial and triaxial compression tests were conducted to obtain stress–strain curves, peak strength, elastic modulus, cohesion, and internal friction angle. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and an improved simulated annealing algorithm for three-dimensional pore reconstruction were used to characterize pore diameter, porosity, connectivity, and hydration products (calcium-silicate-hydrate (C-S-H), calcium-aluminosilicate-hydrate (C-A-S-H), and sodium-aluminosilicate-hydrate (N-A-S-H)). The results show that increasing confining pressure flattens the post-peak softening curve and transitions failure from brittle to ductile, while rising curing temperature shortens the compaction stage and increases elastic modulus. Both factors increase peak strength synergistically. Cohesion increases nonlinearly with temperature (2.64 MPa at 5 °C to 6.27 MPa at 50 °C), whereas the internal friction angle (13°) is temperature-insensitive. Microscopically, confining pressure reduces pore diameter, porosity, and connectivity via physical compaction; curing temperature promotes gel production, decreasing porosity from 26.23% to 13.95% and connectivity from 64.87% to 34.89%. This study provides a theoretical basis for backfill design and ground pressure management in open-pit end-slope mining. Full article

Conventional ureolytic microbial soil stabilization can generate ammonium-containing by-products and may show reduced treatment uniformity in deep soils where mass transport is limited. This study investigated the feasibility of using facultatively anaerobic yeast to stabilize loess under aerobic and anaerobic curing conditions. Specimens were prepared using a single-mixing method and cured for 3, 7, 14, and 28 days. Unconfined compression tests, unconsolidated–undrained triaxial tests, scanning electron microscopy, X-ray diffraction, and acid-washing analysis were conducted. Yeast treatment increased the unconfined compressive strength of loess to 99.8–109.9 kPa under aerobic curing and 89.1–95.7 kPa under anaerobic curing, compared with 81.3 kPa for untreated loess. Cohesion increased from 25.30 kPa to 27.24–33.14 kPa, whereas the internal friction angle remained within 37–39°. Microstructural observations revealed fibrous and film-like bonding materials between soil particles, while no obvious newly formed crystalline calcium carbonate was detected. The acid-washing results also indicated no evident net increase in calcium carbonate content. The strengthening effect was therefore attributed mainly to particle bonding associated with polymeric or extracellular-polymeric-substance-like products, rather than extensive calcium carbonate precipitation. These results demonstrate the potential of yeast as an environmentally friendly biological agent for loess stabilization. Full article

Cold spray additive manufacturing (CS) has emerged as a transformative solid-state deposition technique for designing advanced functional surfaces with tailored tribological performance. By accelerating micron-scale particles to supersonic velocities and depositing them below their melting point, CS enables the fabrication of dense, oxidation-resistant coatings with strong metallurgical bonding and beneficial compressive residual stresses. These distinctive attributes create unique opportunities for the design-driven engineering of wear-resistant surfaces across aerospace, automotive, marine, biomedical, and industrial sectors. Despite a growing literature on CS processing and properties, a comprehensive framework linking design principles encompassing material selection, coating architecture, process parameter optimization, and post-processing strategies to tribological outcomes is absent from the field. This review addresses that gap by critically examining the design space of CS coatings and positioning tribological performance as an outcome of deliberate engineering decisions. The relationships between coating architecture and tribological behavior, specifically friction control, wear resistance, adhesion-cohesion integrity, and surface roughness, are examined under varying environmental and loading conditions. Design strategies involving composite and hybrid coatings incorporating solid lubricants, ceramic reinforcements, and nanostructured architectures are discussed in the context of achieving specific functional objectives. The influence of process parameters, such as particle velocity, gas temperature, substrate preparation, and post-treatments including heat treatment, friction stir processing, and laser shock peening, on tribological outcomes is critically synthesized. Environmental performance under high-temperature, corrosive, and extreme wear conditions is analyzed through a design lens. A design decision framework summarizing material-process-property linkages for CS tribological coatings is presented to provide practical guidance for engineers and researchers. Future directions include AI-driven process optimization, multi-material architectures, and the integration of CS within broader design-for-manufacturing workflows. Full article

Gravel soil used as backfill behind rockfall barriers in mountainous roads can extend structural service life and support sustainable resource utilization. However, rainfall-induced erosion may cause soil loss and reduce its buffering capacity. The fibers are short discrete fibers with a length of approximately 12 mm and an average diameter of 32.7 μm, corresponding to an aspect ratio of approximately 367. Reinforcement is achieved through fiber–soil interaction mechanisms, including particle bridging, interfacial friction, and pull-out resistance. The effects of polyurethane and fiber contents on compressive strength, shear strength, and impact resistance were evaluated using response surface methodology. Scanning electron microscopy was used to examine the microstructural features associated with the reinforcement mechanisms, and engineering-scale model tests were conducted to assess erosion and impact resistance under representative service conditions. The results show that polyurethane and fibers produce significant nonlinear enhancement effects on the mechanical properties of gravel soil, mainly through their individual contributions, whereas their interaction is limited. Multi-objective optimization indicates that the optimal mixture contains 6.8% polyurethane and 0.19% fiber, with prediction errors below 5%. The unconfined compressive strength of the gravelly soil increased from 107.6 kPa to 931.5 kPa, representing a 765.7% increase. Cohesion increased from 23.4 kPa to 83.44 kPa, representing a 256.4% increase. The internal friction angle increased from 43.4° to 61.23°, corresponding to a 41.08% increase. Under 1 h of intense rainfall erosion, the stabilized soil exhibited only slight surface particle detachment and maintained overall integrity. In impact tests, the velocity attenuation rate reached 65.6–71.4%. The proposed material provides a sustainable solution for improving buffer layers in rockfall barriers. Full article

Silts are generally unsuitable for direct use as subgrade fill material due to their low shear strength and deformation resistance. In this study, a novel technique for strengthening silt using enzyme-induced calcium carbonate precipitation (EICP) with the addition of non-fat milk powder is proposed to improve the mechanical properties of silt for use as subgrade fill material. The effect of EICP on the mechanical properties of silt, in terms of internal friction angle and shear strength, was examined through consolidated undrained (CU) triaxial shear tests. The results showed that, with the EICP technique involving non-fat milk powder, the mechanical behaviors of silts were significantly enhanced due to the improved bonding ability of the silt particles. Furthermore, an optimum content of non-fat milk powder of 6 g/L is proposed to increase the mechanical properties. Compared with EICP treatment alone, under the optimum condition of 6 g/L non-fat milk powder and 14 days of curing, the shear strength, cohesion, and internal friction angle increased by 44.1%, 51.86%, and 31.4%, respectively. Finally, microstructural analyses were conducted using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) to provide insight into the mechanisms underlying the improvement of silt. The findings of this study can provide guidance for the application of silt improvement through the EICP technique involving non-fat milk powder. Full article

Mine tailings are highly disturbed technogenic materials whose low mechanical stability may limit mine closure and long-term land rehabilitation. This study evaluates the geomechanical potential of Chrysopogon zizanioides (L.) Roberty, commonly known as vetiver grass, to improve the shear-strength response of filtered mine tailings under controlled laboratory and numerical modelling conditions. The study does not constitute field-scale validation of phytostabilization; rather, it examines the contribution of vetiver roots to apparent cohesion and shallow slope stability. A combined experimental–numerical framework was implemented, including laboratory characterization of unreinforced and root-reinforced tailings, derivation of Mohr–Coulomb shear-strength parameters, and limit-equilibrium slope-stability analysis under predefined root-growth and root-orientation scenarios. The results indicate that vetiver roots increased apparent cohesion by up to 34.6%, whereas changes in friction angle remained below 10%, suggesting that the dominant reinforcement mechanism is pseudo-cohesive rather than frictional. The calculated factors of safety varied according to slope geometry, assumed root length, root orientation, and simplified water-condition scenarios. However, the findings remain limited to controlled experimental and numerical conditions. Field-scale validation, long-term root monitoring, moisture variability, nutrient availability, phytotoxicity, contaminant immobilization, and life-cycle performance should be assessed before practical implementation. This study provides preliminary geomechanical evidence of vetiver-induced root reinforcement in filtered mine tailings. Full article

Cementitious materials in the fresh state are commonly regarded as viscoplastic. That is, below a given yield stress, they exhibit solid-like behavior, whereas above this threshold, they behave as fluids. In this context, the shear strength of such materials has traditionally been analyzed from a rheological standpoint, considering them as fluids and using time as the primary state variable. From a structural perspective, however, relatively few studies have treated the material as a solid. With the advent of 3D printing technology, this trend has persisted. Within this framework, the present research aims to evaluate the shear strength of a structural mortar for 3D printing in its solid-like regime, by applying the Mohr–Coulomb failure criterion. Furthermore, in a novel approach, the degree of hydration of Portland cement is proposed as a state variable to replace time, enabling a more comprehensive and objective description of the material’s mechanical evolution. Thus, addressing this gap in the state of the art, a chemo-mechanical coupling is developed. To obtain the necessary data, direct shear, uniaxial compression, and isothermal calorimetry tests are performed. The results indicate that the friction angle remains constant, at approximately 33°, and that cohesion, the parameter governing strength gain, exhibits the same linear rate of increase with hydration in both mechanical tests, indicating an intrinsic relationship within the material. Full article

Weld-bonded joints combine localized metallic welding with structural adhesives and are increasingly used in lightweight multi-material structures. Although numerous studies have examined individual weld-bonding processes, the available literature remains fragmented with respect to process classification, adhesive–weld interaction and mechanical performance. This paper presents a critical review of hybrid weld-bonded joints published between 2000 and 2026, with emphasis on welding-based joining processes and their influence on joint behavior. The main weld-bonding techniques, including resistance spot weld-bonding (RSWB), friction stir weld-bonding (FSWB), friction stir spot weld-bonding (FSSWB) and laser weld-bonding (LWB), are systematically compared in terms of heat input, adhesive stability, load transfer mechanisms and mechanical performance. The analysis indicates that processes with lower heat input, such as FSWB and FSSWB, provide improved adhesive preservation and fatigue performance, whereas RSWB remains the most industrially established solution. The influence of different adhesive families (epoxy, polyurethane, acrylic and thermoplastic) is evaluated with respect to thermal resistance, rheological behavior during welding and long-term durability. Mechanical performance under static, fatigue and impact loading is critically assessed, highlighting typical strength improvements compared with purely welded joints and identifying dominant failure modes. In addition, numerical modeling approaches, including finite element and cohesive zone methods, are reviewed in terms of their ability to capture coupled thermomechanical and damage phenomena. The review further outlines key industrial applications, current technological limitations and future research directions, including advanced adhesive systems, low-heat-input processes, non-destructive testing and digital-twin-based optimization. Full article

Completely weathered granite residual soil is a weathering-derived, soil-like geomaterial whose shear strength is difficult to characterize using only conventional small-scale laboratory tests. This study evaluated the effects of specimen size and material structure by comparing in situ direct shear tests, conventional laboratory direct shear tests on undisturbed and remolded specimens, and large-scale laboratory direct shear tests on remolded specimens with box sizes of 150, 200, and 250 mm. The results show that undisturbed specimens exhibited higher shear strength than remolded specimens, indicating a clear structural contribution. With increasing specimen size, cohesion decreased from 41.2 to 31.4 kPa, whereas the friction angle increased from 35.3° to 40.6°. Compared with the conventional undisturbed test, the in situ tests yielded lower cohesion but higher friction angles. These results indicate that both size effect and structural disturbance significantly influence the interpretation of shear strength parameters in completely weathered granite residual soil. For engineering design in weathered-granite terrains, strength parameters derived from larger specimens or in situ tests are likely to be more representative than those obtained from conventional small-scale laboratory tests. Full article

Background/Objectives: Co-processed excipients (CPEs) are designed for direct compression through particle engineering, yet comprehensive powder rheological profiles systematically comparing advanced and traditional characterization methods remain limited. This study characterized fifteen lactose-based excipients using European Pharmacopoeia (Ph. Eur.) methods and the complete Freeman FT4 Powder Rheometer measurement suite, establishing a correlation framework linking particle-level attributes to macroscopic flow behavior. Methods: Fifteen excipients were characterized for bulk and tapped density, compressibility index, flow time (Ph. Eur. 2.9.16), and angle of repose (Ph. Eur. 2.9.36). Particle size and shape were measured by dynamic image analysis. FT4 measurements comprised stability and variable flow rate testing, consolidation, aeration, compressibility, permeability, shear cell, and wall friction at three surface roughness. Pearson correlation matrices were computed across all 53 parameters. Results: Classical flow indices classified most CPE as good-to-satisfactory, failing to discriminate materials with fundamentally different dynamic flow profiles. FT4 testing revealed a fourfold range in Basic Flowability Energy (624–2107 mJ), a ninefold range in flow function coefficient (4.3–35.8), and wide aeration sensitivity differences (Aeration Ratio: 1.9–283.7). Strong correlations were identified between Specific Energy and compressibility index (r = 0.85), cohesion and Flow Rate Index (r = 0.79), and Normalized Aeration Sensitivity and pressure drop (r = 0.86). Within-family comparisons (Tablettose 70/80/100, FlowLac 90/100) revealed that particle size distribution breadth is a more critical flow determinant than median size alone. Conclusions: Combining FT4 rheometry with pharmacopoeial testing provides substantially greater discriminating power than either approach alone, enabling rational excipient selection for direct compression formulation. Full article

The mechanical performance of joints in prefabricated subway stations is a key factor governing the overall structural stability. This study investigates the grouted mortise–tenon joint (GMTJ), which is widely used in prefabricated subway station structures. A refined finite element model was established by incorporating material nonlinearity and a cohesive–friction hybrid constitutive model for the grout–concrete interface, and the accuracy of the model was validated against experimental results. Using the prototype GMTJ from an engineering project as the baseline, parametric analyses were conducted considering three concrete strength grades (CSGs) and three longitudinal reinforcement ratios (LRRs). The results show that increasing the CSG improves the joint’s flexural capacity and delays crack propagation. Although a higher LRR enhances the overall deformation resistance, an excessively high LRR intensifies stress concentration in the tenon region due to the absence of reinforcement in this area. Therefore, merely increasing the LRR cannot effectively improve joint durability, and local reinforcement of critical components such as the tenon is recommended in practical engineering. These findings provide meaningful references and insights for the structural design of prefabricated subway station joints. Full article