Search Results (1,470)

To investigate the mechanical response and evolutionary mechanisms of shear-slip rockburst in fractured rock masses, intact, single-fracture, and double-fracture cubic specimens were fabricated using a self-developed synthetic material designed to reproduce pronounced elastic energy storage and rapid brittle failure. Shear-slip tests were conducted under normal stresses ranging from 0.9 to 3.6 MPa. The impact energy index, elastic energy index, and dynamic failure time of the material were 18.0, 9.2, and 140 ms, respectively. Shear stress, shear displacement, and normal displacement were monitored synchronously, while stress-drop events, shear-surface damage, and rock-powder mass were analyzed to clarify the controlling effects of normal stress and the fracture configuration. The results showed that, as the normal stress increased from 0.9 to 2.7 MPa, asperity interlocking along the shear surface was enhanced, resulting in overall increases in the peak and residual shear strengths and progressive suppression of dilation. At 3.6 MPa, all three specimen types exhibited pronounced stress drops, normal contraction, and complete loss of shear-bearing capacity, indicating a transition from stable frictional sliding to crushing collapse dominated brittle instability. The tested specimens suggest that increasing the number of prefabricated fractures may promote deformation localization and shorten the stable post-peak sliding process. At 3.6 MPa, the shear displacements corresponding to complete instability of the intact, single-fracture, and double-fracture specimens decreased from 9.0 to 7.8 and 6.5 mm, respectively, whereas the maximum stress drops increased from 0.28 to 0.62 and 0.90 MPa. These responses were characterized by earlier instability, increasingly concentrated stress-drop events, and larger individual stress drops. With increasing normal stress, the mass of rock powder increased from 11 to 56 g, indicating that shear surface damage evolved from localized fracturing to intensive crushing and grinding. The shear-slip process comprised four stages: compaction adjustment and load-bearing structure formation, elastic shearing and energy accumulation, damage accumulation and crack coalescence culminating in peak instability, and fragment reorganization with post-peak sliding. These findings provide experimental evidence for identifying shear-slip dynamic instability in fractured surrounding rock. Full article

To address the excessive differential settlement and the bridge approach bump problem behind bridge abutments in binary strata under cyclic vehicle loading, a highway bridge abutment in western China was investigated as a case study. Through field sampling and laboratory dynamic triaxial tests, the dynamic parameters of the loess-like silt under cyclic loading were calibrated. A three-dimensional dynamic numerical model considering a pile–soil–structure interaction was established. The bridge approach settlement, horizontal displacement, and dynamic responses of abutment pile foundations before and after high-pressure jet grouting reinforcement were compared and analysed. Furthermore, the evolution of reinforcement effectiveness under different axle loads (40–150 [kN]) and vehicle speeds (40–100 [km/h]) was systematically investigated. The results indicate that high-pressure jet grouting can significantly control bridge approach settlement and horizontal displacement, with reductions of 80.5% in settlement and 78.0% in horizontal displacement at the bridge–embankment transition zone. Settlement and horizontal displacements of the pile foundation at shallow depths are effectively suppressed, the stress distribution along the piles becomes more uniform, and stress concentration at the soil–rock interface is notably alleviated. The influence of axle load on reinforcement effectiveness is far greater than that of vehicle speed, with 80 [kN] identified as the critical load for deformation control of the reinforcement system. Within the conventional speed range of 40–100 [km/h], the effect of speed variation on the deformation of the reinforced zone is limited, and the jet grouting reinforcement system maintains a stable control performance. The findings provide a theoretical basis and technical support for the design and maintenance of jet grouting reinforcement against bridge approach settlement in binary strata. Full article

Ultra-deep circular shafts are increasingly deployed in congested urban environments, yet their structural performance in highly sensitive soft clay remains susceptible to diaphragm wall panel joints, structural imperfections, and complex interactions with adjacent structures. This study presents a high-fidelity three-dimensional (3D) numerical investigation into the excavation behavior of an ultra-deep circular shaft with a diameter of 30 m and an excavation depth of 56.3 m in Shanghai soft clay by synthesizing high-resolution field monitoring with advanced finite element modeling. The numerical framework was established in PLAXIS 3D utilizing the Hardening Soil model with small-strain stiffness (HSS), explicitly incorporating an equivalent structural stiffness reduction scheme (0.8 vertically and 0.5 circumferentially) to capture panel segmentation, joint compliance, and concrete cracking. The reduced-stiffness model successfully reproduces the measured deep-seated bulging profiles and internal force distributions with high fidelity. The findings reveal exceptional deformation control capabilities of the circular geometry, yielding a maximum lateral wall deflection of merely 9.1 mm (0.016%H_e), which is significantly smaller than the normalized deformation ratio of 0.3%H_e observed in five analogous rectangular excavations in Shanghai. The numerical results indicate that circumferential compression governs the overall load transfer behavior, while vertical bending response remains relatively limited. Furthermore, a pronounced circumferential anisotropy in wall deformation is governed by asymmetric boundary conditions, where localized Metro Jet System (MJS) ground improvement significantly restrain movements, whereas the non-grouted area experience peak deflections. Crucially, interaction with the adjacent external diaphragm walls of ancillary structures induces a complex 3D stress redistribution rather than a beneficial shielding effect, amplifying the peak shaft wall displacement by nearly 62.8% (from 4.73 mm to 7.70 mm). These insights underscore the criticality of integrating small-strain soil mechanics, equivalent structural degradation, and adjacent structural boundaries into predictive design protocols for ultra-deep circular retaining systems. Full article

Grouted connection segments are key load-transfer components in offshore wind jacket structures, and their axial compressive performance is essential for the safety and reliability of the foundation system. This paper develops a finite element model of a grouted connection segment incorporating steel-fiber-reinforced high-strength grout to investigate its mechanical behavior and parametric effects under axial compression. A 1:7-scale model test is conducted to verify the numerical model through comparisons of the load–displacement response and strain responses at key locations. The steel tubes are simulated using a trilinear hardening elastoplastic model, while the steel-fiber-reinforced high-strength grout is represented using the concrete damaged plasticity model with corresponding tensile and compressive constitutive relationships and damage parameters to characterize its nonlinear response. Based on the validated model, a full-scale numerical model is established to analyze the effects of steel tube thickness, shear key spacing, shear key height, and shear key width using the control variable method. The results indicate that steel tube thickness has the most significant influence on the ultimate bearing capacity and can improve the load-bearing capacity and ductility of the structure. Shear key spacing mainly affects axial stiffness and deformation compatibility, while shear key height and width have limited effects on the ultimate bearing capacity but contribute to local deformation control and stiffness enhancement. The findings provide a validated numerical basis for evaluating the axial compressive behavior of steel-fiber-reinforced grouted connections and offer a useful reference for the design and parameter optimization of grouted connection segments in deep-water offshore wind jacket structures. Full article

This study investigates the compression and impact responses of three brachistochrone-inspired lattice topologies, namely, Gyroid, Body-Centered Cubic (BCC), and Interconnected Wavelet Packet (IWP), fabricated by additive manufacturing using Elastic 50A Resin V2. Quasi-static compression tests were performed to characterize the force–displacement response of each topology, and drop-weight tests were conducted to measure the corresponding acceleration histories under impact loading. Based on the compression data, two restoring-force descriptions were evaluated for dynamic prediction: a fractal dynamic model with polynomial restoring force and the Equivalent Energy Spring Model (EESM). The results show that lattice topology strongly affects deformation mode, compressive stability, and energy absorption. The B-IWP lattice exhibited the highest energy-absorption capacity but also showed greater susceptibility to buckling, whereas the B-BCC topology provided a more balanced combination of structural stability and impact-mitigation capability. Comparison with the experimental impact responses showed that both modeling approaches reproduced the main features of the measured acceleration histories, while the EESM generally provided better agreement with the experimental data. These findings demonstrate that compression-derived restoring-force models provide an effective framework for predicting the impact behavior of brachistochrone-inspired lattices and support their design for protective packaging and other impact-critical applications. Full article

A demand-oriented spatial reinforcement scheme was developed for circular anti-slide piles subjected to a known dominant direction of landslide thrust. Based on the depth-dependent bending-moment and shear-force demands, the proposed scheme integrates uniformly distributed full-length base bars, supplementary longitudinal reinforcement concentrated within the principal tension sector, depth-dependent termination of longitudinal bars, and variable-pitch spiral reinforcement. A three-dimensional nonlinear finite-element model was established to compare the proposed scheme with a conventional circumferentially uniform reinforcement arrangement under identical geometrical, material, loading, and boundary conditions. The results showed that the proposed scheme reduced the total reinforcement volume from 1.243 to 1.041 m³, corresponding to a reduction of 16.3%. At 40% of the design load, the pile-head displacement increased slightly by 3.96%, indicating a minor reduction in initial stiffness. Under the full design load, however, the pile-head displacement, maximum longitudinal-bar stress, and maximum equivalent plastic strain decreased by 5.48%, 15.7%, and 34.5%, respectively. The concrete damage distribution also became more localized and discontinuous near the critical region. These results demonstrate that demand-oriented spatial reinforcement can improve reinforcement utilization, reduce local response concentration, and enhance deformation control under high load levels while achieving substantial steel savings. Full article

Small-scale clay-brick yards require molding equipment that increases output while remaining mobile, locally serviceable, and compatible with intermittent material supply. This article documents the functional architecture and exploratory operational performance of the mobile 12-cavity hydraulic clay-brick molding machine (ML12). Its design contribution is the integration of a dimensioned wheeled steel chassis, seated paired-lever controls, a translating feed hopper/distributor, a 12-cavity mold, two vertical hydraulic actuators, and a water-spray cleaning subsystem in a four-stage operating cycle. A retrospective concept-appraisal matrix compares this architecture with fixed automated and mobile manual concepts; equal weighting and one-at-a-time ±25% weight variations preserve the ML12’s highest internal score, without establishing stakeholder preference or empirical superiority. The evidence base also comprises sequential daily production logs: ten days of traditional manual molding followed by ten days of ML12-assisted molding. Mean gross green-brick output was 720 ± 86 bricks/day in the traditional period and 1495 ± 16 bricks/day in the ML12 period; corresponding descriptive throughputs were 86.5 and 186.9 bricks/h. A rejection-rate sensitivity analysis shows that, if traditional production had no rejects, ML12 conforming output would equal the traditional gross mean at a 51.8% ML12 rejection rate; this quantity boundary is not an estimate of quality or economic break-even. A preliminary linear-static finite-element case for a reconstructed frame returned a maximum von Mises stress of 112.3 MPa, 1.82 mm resultant displacement, and a minimum elastic safety factor of 2.23 on the reported medium mesh; the result is limited to the specified 1.0 kN load case and is not structural certification of the complete machine. Because the operational comparison was non-randomized and did not control staffing, operators, clay batch, moisture, weather, energy use, or rejection rate, the observed difference cannot be attributed exclusively to the machine. The results establish the machine architecture, an operational signal, and a bounded preliminary frame response, but not brick quality, ergonomic benefit, full structural safety, environmental benefit, or commercial return. Full article

In deepwater open-loop drilling of ultra-shallow high-build-rate horizontal wells, the drill string spans the exposed seawater section, the mudline transition, and the constrained downhole section. Existing studies have not yet established a unified coupled dynamic model covering the full string, and the response patterns and parameter-control mechanisms remain insufficiently understood. This study examines a surface-hole operation in a block of the South China Sea. A six-degree-of-freedom spatial Euler–Bernoulli beam finite element model was established from the measured wellbore trajectory. Structural and fluid inertia, geometric stiffness due to axially varying force, Morison-type current loading, a wake-oscillator model for vortex-induced vibration (VIV), wellbore contact and friction, and bit loads were coupled within one framework. The generalized-alpha method was used for time discretization, and the nonlinear dynamic equilibrium equations were solved by within-step iteration for multiple operating conditions. Under the baseline condition, the peak in-line displacement was 6.3–6.4 m and occurred in the middle of the seawater section; the peak cross-flow displacement was approximately 0.43 m, the maximum bending moment was approximately 36 kN m, and the maximum equivalent stress was approximately 230 MPa. The high internal-force values were concentrated in the mudline transition and the upper BHA, demonstrating spatial separation between deformation and internal force. Surface current velocity controlled the in-line response amplitude: increasing the velocity from 0.4 to 0.8 m/s increased the peak in-line displacement by approximately 230%. WOB had a limited effect on global deformation and acted mainly on the local near-bit section. These results provide numerical reference for mechanistic analysis and parameter control of drill-string dynamics in comparable deepwater open-loop drilling operations. Full article

External loads acting on shield tunnel linings in service are difficult to determine, while existing back analysis methods often require multiple monitoring quantities and repeated numerical calculations. This study develops an analytical method for identifying the equivalent horizontal load and lateral pressure coefficient from a single rotation measurement. The lining is modelled as a continuous Euler–Bernoulli curved beam on a radial Winkler foundation, with circumferential compression and bending considered. The radial components of the vertical and horizontal loads are decomposed into uniform and second-order terms. Closed-form solutions are obtained for displacement, rotation, and internal forces, followed by an explicit inverse relation between rotation at one circumferential position and the load difference. The analytical responses agree closely with an independent plane-frame finite element model. Prescribed horizontal loads and lateral pressure coefficients are also recovered accurately from finite element rotations. A FLAC3D model of the complete ring with continuous elastic ground further shows that the circumferential response pattern is retained and that the equivalent horizontal load can still be estimated when the Winkler ground representation is relaxed. The method identifies the load difference from one rotation measurement, and when the vertical load is independently estimated, determines the equivalent horizontal load. It provides a basis for assessing lining ovalization, bending response, and abnormal loading states. Full article

This study aims to investigate the influence of non-local elasticity on the coupled optoelectronic photo-thermoelastic response of an anisotropic fiber-reinforced silicon half-space subjected to optical carrier excitation. A coupled analytical model is developed by incorporating non-local elasticity into a fiber-reinforced anisotropic semiconductor framework, where the thermal, carrier-density, displacement, and stress fields are fully coupled. After introducing the appropriate non-dimensional variables, the governing equations are transformed using the normal-mode technique into a system of ordinary differential equations and solved analytically through an eigenvalue-based vector–matrix approach. The novelty of the present work lies in examining the influence of the non-local parameter within a fiber-reinforced anisotropic semiconductor and performing a systematic comparison between fiber-reinforced and non-reinforced configurations under identical photothermal loading conditions. The numerical results demonstrate that increasing the non-local parameter produces pronounced changes in the mechanical response, including displacement amplitudes, stress distributions, and wave attenuation characteristics, whereas the temperature and carrier-density fields exhibit only slight variations within the investigated parameter range. Fiber reinforcement further influences the mechanical response by enhancing the structural stability and directional stiffness of the medium. The proposed analytical framework provides physical insight into the coupled effects of nonlocality and fiber reinforcement, with potential relevance to the analysis and design of semiconductor devices, optoelectronic and photonic structures, MEMS/NEMS, and smart fiber-reinforced composite materials operating under coupled thermo-mechanical and optical excitations. Full article

The long-term preservation of earthen wall heritage in Shanxi largely depends on the stability of its rammed earth walls. In this study, the ancient city wall site of Guoyang in Shanxi is taken as a case study. Samples are collected from four directional sections (brick, mortar, and rammed earth), and a nonlinear dynamic finite element method (FEM) with horizontal impact loading is applied, combined with microscopic analyses (SEM, XRF, XRD), to investigate the deterioration mechanisms and structural responses of the brick wall surface. The results show that (1) under identical stress, the north wall exhibits smaller displacement (2.942 × 10⁻² mm) than the south wall (4.058 × 10⁻² mm), indicating greater lateral stiffness and deformation resistance; (2) the rammed earth particles on the north side show the highest uniformity (CV = 0.4981), while those on the west side display the greatest dispersion (CV = 0.9852), revealing pronounced differences in microscopic stability among the different wall orientations; (3) the north-side rammed earth exhibits a composition typical of high-quality traditional ternary lime–soil mixtures, characterized by high SiO₂ (47.06%), high CO₂ (19.73%), and low Na₂O (2.358%); and (4) the durability of the four wall sections varies with distinct deterioration characteristics. Mineral composition and environmental factors jointly contribute to the differences in wall color and surface conditions. This study provides a reference for the conservation and restoration of similar rammed earth heritage sites. Full article

Mainstream airport runway roughness indices and aircraft–runway coupled vibration studies are constructed under the implicit centreline taxi assumption, leaving the random lateral deviation of the actual aircraft trajectory outside the coupled vibration framework. Existing studies have revealed the importance of lateral deviation from the perspectives of wheel track distribution and cumulative damage; however, these approaches mainly treat lateral deviation as an exogenous statistical input for damage evaluation without embedding it into the aircraft–runway coupled vibration equations to resolve the joint probability evolution of the aircraft, wheel load and pavement responses. Unlike existing centreline- or fixed-wheel-path aircraft–runway coupled vibration models, this study embeds aircraft lateral deviation as a random variable into the wheel–pavement contact coordinates and the displacement–compatibility relation so that the three-dimensional runway roughness input varies randomly with the actual wheel path and further solves the probability distributions of the aircraft-side and pavement-side responses through PDEM. The IPDEM solution was cross-validated against 10,000 Monte Carlo simulations, with PDF shape deviations within 5% and mean/standard deviation within 3%. Results show that the centre-of-gravity acceleration reaches a coefficient of variation (COV) of 47.99% (about 3.7 times the 12.98% induced by aircraft weight randomness alone), and the main-landing-gear dynamic load coefficient COV reaches 1.84% (again, 2.9 times the 0.63% for weight randomness); the pavement bottom strain and vertical displacement attain COVs of 1.50% and 2.03%, respectively. Within the cases and comparison scope of this study, lateral deviation randomness is an important source of dispersion in the aircraft-side responses, and the CGA and DLC variability this induces is higher than that under aircraft weight randomness alone, providing a probabilistic baseline for reliability-based runway design and full-cross-section roughness evaluation. Full article

Heavy-duty freight electric locomotives, characterized by their enormous axle loads and complex operating conditions, are prone to unstable deformation modes in their front-mounted deformable energy-absorbing components when subjected to sudden axial impact loads. Such instability often leads to premature damage or functional failure, posing a serious threat to operational safety. Although extensive studies exist on thin-walled absorbers for passenger vehicles and railcars, the research on heavy-haul locomotive-specific structures under high kinetic energy conditions is scarce, and the coupled effects of triggering groove number, wall thickness, crushing displacement, and groove outer diameter have rarely been systematically investigated. Moreover, the inherent trade-off between lowering initial peak force and increasing mean crushing force remains unresolved in current designs. Motivated by this gap, the present study develops and validates a finite element model and then conducts a parametric study to reveal the influence of the four structural parameters. A multi-objective surrogate model for energy absorption, initial peak force, and mean crushing force is built using design of experiments (DOE) and response surface methodology (RSM), followed by Pareto optimization using the neighborhood cultivation genetic algorithm (NCGA). The optimized configuration improves stability by 6.72%, energy absorption by 17.68%, and means crushing force by 8.33%, while maintaining a relatively low peak force, thereby significantly enhancing overall crashworthiness. This work provides a valuable numerical reference and practical optimization guidelines for deformable energy-absorbing components in heavy-haul freight electric locomotives. Full article

Fused Deposition Modelling (FDM) is one of the most widely adopted additive manufacturing technologies, and polylactic acid (PLA) has emerged as a commonly used feedstock material owing to its biodegradability and low cost; however, the mechanical performance of FDM-printed PLA components is significantly influenced by their internal infill structure. This study systematically investigates the design of infill structures in 3D-printed PLA components with the dual objectives of minimising structural mass while maximising mechanical strength. Standard tensile specimens with three infill topologies-honeycomb, grid, and triangular-at three infill density levels (20%, 40%, and 60%) were fabricated and subjected to uniaxial tensile testing, while three-dimensional nonlinear finite element models were concurrently developed in ABAQUS to simulate their tensile response. The experimental results demonstrate that the tensile strength and Young’s modulus of the honeycomb structure increase continuously with increasing infill density, with the honeycomb topology exhibiting the highest tensile strength across all density levels. Its Young’s modulus increases from 0.180 GPa at 20% density to 0.540 GPa at 60% density, representing a 200% increase; the Young’s modulus of the grid structure increases monotonically with infill density, reaching its maximum at 60% density; whereas the Young’s modulus of the triangular structure is highest at 20% density and decreases with increasing density, a trend potentially associated with topology-dependent stress concentrations and manufacturing-induced micro-defects at higher infill densities. The finite element results show good agreement with the experimental data, with maximum relative errors of 1.39% for peak load and 10.81% for fracture displacement, indicating the predictive capability of the model within the investigated parameter range. The honeycomb structure exhibits the best overall performance across the investigated density levels and achieves the highest specific strength at low density. Building on these findings, the infill structure was further optimised using a Kriging surrogate model in conjunction with the Non-dominated Sorting Genetic Algorithm II (NSGA-II), yielding a high-quality Pareto front. The optimisation results identify the honeycomb structure with an infill density of 0.378 as the recommended trade-off solution, achieving a 62.2% reduction in nominal material usage while retaining approximately 80.0% of the tensile strength of the solid reference. Based on the experimental, numerical, and optimisation results, four categories of engineering design guidelines are proposed, covering infill structure selection, optimal density range, scenario-based application, and gradient infill design, providing both theoretical support and practical guidance for the performance-driven design of 3D-printed PLA components for lightweight applications in aerospace, automotive, and related industries. Full article

This study compares the low-temperature responses of two SBS-based asphalt mixtures under progressive step loading: a 4% SBS-modified control mixture and a composite mixture containing 3% SBS + 1.0% Nano-SiO₂. Progressive three-point bending creep tests were conducted at 0 °C, −10 °C, and −20 °C to evaluate their mechanical and time-dependent responses. Furthermore, a reduced offset-power-law equation motivated by the first-order small-argument expansion of the fractional-order representation was calibrated to the recorded within-stage creep curves and subsequently used for a model-based time-domain interpretation. The reduced equation captured the main features of the recorded within-stage curve shapes under the tested conditions and provided stage-specific descriptors for comparing the recorded time-dependent responses. In the retained records, the measured flexural tensile strength and maximum flexural tensile strain values were higher for the composite formulation than for the 4% SBS-modified control under the tested temperature conditions. Under the tested step-loading conditions, the retained stage curves showed formulation-dependent within-stage displacement responses. The observed differences are interpreted at the formulation-comparison level rather than as isolated Nano-SiO₂ effects. The comparison is limited to the retained records for the two prescribed formulations at the common 5.2% asphalt-to-aggregate ratio and does not quantify between-specimen variability. Together, the measured flexural indicators and model-derived stress-retention responses describe a temperature-dependent balance among deformation accommodation, flexural resistance, and modeled stress retention. Full article