Search Results (435)

To investigate the settlement response and rectification performance of existing tilted high-rise buildings during staged underexcavation in complex collapsible-loess areas, a severely tilted high-rise building was selected as the case study. An integrated approach combining field investigation, geotechnical testing, a 1:100 physical model test, and three-dimensional finite-element analysis was employed to investigate the causes of building inclination and the deformation response during staged underexcavation rectification. The results indicate that insufficient compaction of the inter-pile soil, together with wetting-induced collapse and mechanical softening, jointly contributed to the development of differential foundation settlement. The stage-wise rectification displacement increments during staged underexcavation decreased successively from 0.85 mm to 0.48 mm and 0.43 mm. The prototype-scale rectification displacement derived from the physical model was 176 mm, corresponding to a rectification rate of 83.17%. As underexcavation proceeded, the additional rectification response induced by each stage generally decreased, exhibiting a progressively attenuating trend. Numerical simulations yielded average rectification rates of 95.73% and 98.44% for the one-time and staged underexcavation schemes, respectively, with a final rectification displacement of 202.10 mm for the staged scheme. Under the investigated conditions, staged underexcavation exhibited better rectification performance than one-time underexcavation. The progressively reduced excavation volumes of 120, 100, and 80 m³, combined with inter-stage stabilization, promoted gradual stress redistribution and deformation adjustment of the structure–foundation–soil system, supporting the feasibility of staged underexcavation under the investigated collapsible-loess conditions. These findings provide a useful reference for the controlled and precise implementation of rectification engineering for tilted high-rise buildings in complex collapsible-loess areas. Full article

Pile foundations transmit structural loads to deeper subsoil strata whenever the soil in the vicinity of the ground surface lacks sufficient strength and stiffness to ensure an adequate factor of safety against ultimate failure or warrant settlements to remain below acceptable limits. In many in situ conditions, piles are embedded in layered subsoil medium. In several circumstances, piles are subjected to tensile loading. Large and high-rise civil infrastructure subjected to wind loading, transport infrastructure under horizontal loading due to moving vehicles, offshore structures withstanding wind and wave loading, underground structures subjected to hydrostatic pressure due to buoyancy, etc., are some examples where tension loads are imparted on the supporting piles. The imparted uplift loads in these tension piles are balanced by the negative skin friction induced at the pile–soil interface. In this paper, an analytical model using systematic application of established upper bound shear stress theory to three-layered soil configurations has been developed to formulate the ultimate uplift capacity of tension piles in three-layered soil. The model adopted appropriate correlations for upper bound interface shear stresses in different soils as well as tensile failure of pile material itself. The developed solution was validated by comparing with available experimental results. Thereafter, a case study was performed to study the influence of the variation of pile geometries and relative stiffness on ultimate uplift capacities. Important conclusions were drawn from the entire study. Full article

Freeze–thaw cycling can alter soil–structure interface response in seasonally frozen regions. This study investigated the direct-shear behavior of a commercially sourced silty-loam–concrete interface subjected to sealed freeze–thaw cycling. A 25-condition mixed-level design based on the standard L25(5⁶) orthogonal array (25 runs with six available five-level columns) considered normal stress, nominal interface roughness, moisture content, and freeze–thaw-cycle number; each main condition was tested once, so the results are interpreted descriptively. Shear strength and shear-induced vertical contraction were measured, and digital image correlation (DIC) was used to characterize surface deformation localization. The level-wise mean shear strength increased with normal stress and approximately linearly with roughness. It changed little between 14% and 18% moisture content and decreased at 22% and 26%; the measured plastic limit was 19.2%. With increasing freeze–thaw cycles, the level-wise mean strength decreased to three cycles, then recovered and approached stabilization. These results provide laboratory-scale evidence under the tested closed-system conditions rather than directly transferable pile-design parameters. 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

When large liquefied natural gas (LNG) storage tanks are constructed on deep non-rock sites, soil–foundation–structure interaction (SFSI) alters the dynamic characteristics of the system and affects the actual control effectiveness of the isolation layer. However, the current understanding of the coupling mechanism between the two remains insufficient. This paper takes a 220,000 m³ full-containment LNG storage tank as the study object and establishes a three-dimensional finite element model of the tank-pile group-site system in ABAQUS. Through comparative analyses of three model configurations, namely a rigid foundation model, a non-isolated model considering SFSI, and a lead-rubber bearing (LRB) isolated model considering SFSI, the SFSI effects and LRB isolation effectiveness are systematically separated. For the SFSI effects, the deep site attenuates medium- and high-frequency content while amplifying the response around approximately 1.6 Hz through site–foundation flexibility, transforming the heightwise acceleration amplification profile from an approximately linear pattern to a curvilinear one that bulges at mid-height, with peak pile-cap accelerations increasing by 25.1–76.9% relative to the rigid-base values. For the LRB isolation performance, the introduction of LRBs shifts the dominant system frequency below 1.0 Hz and reduces the maximum tank-wall acceleration amplification factor from 2.64 to 0.81. The resulting attenuation of superstructural inertial forces leads to reductions of 49.6–82.0% in pile-head shear and 57.4–78.0% in near-head bending moment, while the outer-to-inner pile-head moment ratio decreases from 2.94 to 1.13, indicating substantially improved pile-group force uniformity. Nevertheless, the beneficial effect of isolation diminishes with depth, and internal forces at abrupt soil-stiffness interfaces remain governed by kinematic interaction that the isolation layer cannot mitigate. The findings of this study can provide references for the seismic isolation design and pile foundation seismic optimization of super-large LNG storage tanks on deep overburden sites. Full article

Aiming at tight farming schedules, slow straw decomposition, and severe soil-borne disease risks in the practical maize straw returning production of China’s wheat–maize double cropping zones, this study developed a field-adapted in situ rapid high-temperature straw composting technology matched with a special composite microbial inoculant. Post-harvest summer maize straw collected from the field was crushed to 3–5 cm; the inoculant group T and water control CK were arranged with three biological replicates. Raw materials were adjusted to 65% moisture and loosely stacked into trapezoidal piles equipped with layered temperature–humidity sensors covered by plastic film for continuous monitoring. After formula and pile structure optimization, the pile temperature exceeded 50 °C within 8 h and stayed at 58–63 °C for 9 days, limiting the composting cycle to within 15 days. Cellulose and lignin degradation reached 56.25% and 50.39%, respectively; available P and K rose by 12.33% and 14.69%, free amino acids doubled; the C/N ratio dropped to 18:1 and the GI exceeded 130%. High temperature enriched functional flora of Bacillus subtilis, Aspergillus niger and actinomycetes, whereas pathogenic Fusarium abundance decreased to less than 1/31 of the initial level. This technology can bring approximately 400 yuan of potential additional benefit per mu, providing an efficient and labor-saving practical candidate for straw returning in regions with a high multiple-cropping index. Full article

The evaluation of the ultimate bearing capacity (UBC) of foundation systems remains a fundamental challenge in geotechnical engineering because of the complex interactions among soil properties, foundation geometry, loading conditions, embedment depth, and soil–foundation behavior. In recent years, artificial intelligence (AI) and deep learning (DL) techniques have emerged as powerful data-driven tools for modeling nonlinear geotechnical systems and improving bearing-capacity prediction. This study presents a comprehensive state-of-the-art review of AI- and DL-based approaches for foundation systems, including shallow foundations, deep foundations, pile foundations, and other geotechnical applications. Major models, including Artificial Neural Networks (ANNs), Deep Neural Networks (DNNs), Convolutional Neural Networks (CNNs), Long Short-Term Memory (LSTM) networks, Transformer models, Graph Neural Networks (GNNs), hybrid AI frameworks, and physics-informed deep learning approaches, are critically reviewed and compared. Particular attention is given to the integration of AI models with numerical methods, including the finite element method (FEM) and finite element limit analysis (FELA). The reviewed studies frequently report lower prediction errors than conventional empirical, numerical, and machine-learning approaches within the evaluated datasets. However, many of the highest reported accuracies are based on laboratory-scale experiments, simulation-generated data, or random train–test partitions of a single database. Consequently, these results may demonstrate effective interpolation within controlled data distributions rather than reliable performance under independent field conditions. Model performance is strongly influenced by dataset origin and diversity, feature selection, validation strategy, overfitting control, and generalization capability. Hybrid datasets combining field, laboratory, and numerical data offer a promising route toward more reliable prediction, but genuine external validation using independent sites, projects, or institutions remains uncommon. Moreover, architectural suitability should reflect the physical structure of the problem: CNNs are appropriate for spatial heterogeneity, LSTMs for time-dependent behavior, Transformers for long-range interactions, and GNNs for mechanically connected systems. Limited field-scale datasets, weak external validation, limited model interpretability, inadequate uncertainty quantification, and persistent data scarcity continue to restrict widespread engineering implementation. Future research should prioritize explainable AI, physics-informed learning, transfer learning, hybrid data frameworks, open benchmark datasets, and multi-site field validation to improve the robustness, transparency, and practical applicability of intelligent bearing-capacity prediction for diverse foundation systems. Full article

To investigate the impact of localized failure in the support structure on the overall safety performance of the excavation pit and the mechanism of subsequent chain failure, model tests were conducted on the failure of internal bracing in an asymmetrically excavated pit. Unlike previous progressive-collapse model tests, which have addressed symmetric excavations only, the present test captures the cross-pit load-transfer mechanisms that arise when the two sides of a pit are excavated to different depths. The crown displacement of the retaining structure, the earth pressure, and the redistribution of internal forces caused by the failure of internal support members were measured. The results show that when an internal support fails, the lateral stiffness of the retaining plate decreases and the plate moves inward toward the pit, causing settlement of the surrounding soil. The horizontal displacement on the deep-excavation side is larger than that on the shallow side. Failure of one support increases the axial force in the adjacent support while reducing the force in supports farther away. The earth pressure increases in regions far from the failed support, owing to the soil arching effect, but decreases in the adjacent region because the large lateral movement of the plate unloads the soil. Within the failed-support region, the retaining piles are more prone to bending failure on the shallow-excavation side. Full article

Prestressed concrete hybrid-reinforced solid square (PCHSS) piles combine strands and rebars for improved ductility. This study presents large-scale shaking table tests (1:2 scale) on PCHSS pile–superstructure systems embedded in soft and stiff clay, subjected to four ground motions with distinct frequency contents. The experimental program systematically captured the evolution of natural frequencies, damping ratios, dynamic earth pressure distributions, bending moment profiles, curvature ductility demands, and post-test cracking patterns. Results reveal that ground stiffness governs the degradation pathway and energy dissipation mode: soft clay exhibited 37.3% frequency degradation (1.33× that in stiff clay), while stiff clay showed a 101% damping increase (>3× soft clay). Long-period ground motions generated maximum curvature ductility demands and peak bending moments 2–3 times those of short-period records under identical PGA, attributed to near-resonance coupling. Pile–soil interaction transitions from compatible deformation to progressive separation with increasing seismic intensity, with gap spacings of 40–53 mm observed in soft clay. Notably, the code-specified 4D reinforcement zone was found insufficient for soft clay foundations, where crack distributions extended to 4D–7D, warranting an extended zone up to 7D. The findings provide experimental benchmarks for numerical model calibration and offer practical guidance for extending hybrid-reinforced precast piles into moderate-to-high-seismicity regions. Full article

Jacket foundations, with their excellent adaptability and economic efficiency, have been increasingly widely applied in medium-deep water areas. However, the scouring and erosion effects in the marine environment, coupled with complex wind-wave loads, have severely restricted the long-term safe service of jacket foundations. In this study, a structure-pile-soil coupled dynamic response model considering the effects of scour depth and changes in wind and wave directions for the jacket-type offshore wind turbine is developed by integrating the wind and wave load generation capability of OpenFAST and the nonlinear pile-soil interaction analysis function of OpenSees. By quantitatively analyzing key response parameters such as tower top displacement, nacelle acceleration, and internal forces of the foundation tower and pile shaft, this study reveals the significant influence of soil stiffness degradation induced by scour on structural dynamic characteristics, and verifies the effective suppression mechanism of the feathering shutdown strategy on structural responses under extreme loads. The research results indicate that scour has a negligible impact on the fundamental frequency of the jacket-type offshore wind turbine structure, while it significantly reduces the high-order frequencies and leads to a substantial increase in pile shaft internal forces; the effect of wind-wave angle intensifies the spatially coupled vibration response of the structure. The study provides important theoretical and technical support for the anti-scour design, multi-directional load assessment, and formulation of safety control strategies for jacket foundations in complex deep-sea environments. Full article

Scour-induced degradation of soil–structure interactions (SSIs) may substantially amplify the dynamic response of monopile offshore wind turbines (OWTs) under combined environmental and seismic loads. To clarify this mechanism and provide guidance for the safety assessment of OWT foundations, this study establishes a coupled numerical model considering wind, wave, earthquake, scour, and SSI effects. Based on this model, the DTU 10 MW OWT is selected as the research object, and its dynamic responses are investigated with different scour morphologies, scour depths, earthquake inputs, and selected soil parameter sets. The results show that scour reduces the lateral stiffness of the soil–structure system, shifts the structural natural frequency toward a lower-frequency range, and amplifies the displacement, acceleration, and stress responses under seismic excitation. With the selected M8 earthquake input, the tower top displacement reaches 4.18 m in the global-2D scour case, which is more than twice that in the non-scoured case. Global scour produces stronger response amplification than local scour because it weakens the SSI constraint around the full circumference of the pile. For the selected soil parameter sets and the adopted p–y formulations, the clayey foundation model produces smaller calculated displacement and stress responses than the sandy foundation model, reflecting differences in the prescribed lateral stiffness and ultimate soil resistance. These results provide comparative insights for the seismic assessment and scour-resistant design of monopile OWT foundations. Full article

Pile foundations used for structures, such as tall buildings and bridges, especially in coastal and heavily flooded areas, experience uncertain lateral loads. The wave action of water applies a lateral load on the pile, which cannot be predicted accurately. However, the impact of the vertical load significantly increases the pile’s lateral capacity. This suggests more specific research is required into this particular area, especially considering the complex interactions involved. This study focused on the lateral strength of a single pile with a vertical load in layered soils. Using an experimental setup, the horizontal deformation of the pile with an increasing applied compression effect in different soil beds was determined. Analyses were extended using FEM for various combinations of clay and sand layers under varying vertical loads. Initially, the vertical behavior of each pile was determined to varying percentages. The results indicate that the lateral capacity of the pile increases significantly up to 60% of the applied vertical load in both sand and clay. But for clay–sand layer combinations, for an applied vertical load, 100% lateral capacity showed 1.34 times improvement. FEM findings are similar to the experimental results; as the vertical load reaches up to 60% on various soil layers, the lateral capacity improves. Full article

Helical piles are increasingly used in foundation engineering due to their rapid installation, economic advantages, and superior structural performance. Their applicability to various soil conditions has led to widespread use in both onshore and offshore structures. Therefore, their behavior under vertical and lateral static loads, as well as repeated cyclic loading, must be thoroughly evaluated. Helical piles are installed by applying torque through the helical plates attached to their shafts, causing disturbance in the surrounding sand. The influence of this disturbance on pile load-bearing capacity should not be overlooked. In this study, large-scale laboratory tests were conducted on helical piles with different helix diameters and configurations in dry dense sand. The effects of installation-induced sand disturbance and bidirectional cyclic lateral loading on the lateral and uplift capacities were investigated. The results showed that installation-induced sand disturbance reduced the lateral capacity, whereas increasing the helix diameter significantly enhanced the uplift capacity. After cyclic loading, the lateral and uplift capacities of the straight pile decreased by approximately 35% and 55%, respectively, while the lateral capacity of the helical piles was maintained. These findings highlight the importance of considering installation-induced sand disturbance and cyclic loading in the design of helical piles in dry dense sand. Full article

Small-scale excavations with depths of approximately 1 to 3 m are widely conducted for purposes such as the repair of underground pipelines. In confined construction spaces, earth-retaining systems consisting of lightweight sheet-piles with struts and walers are frequently used. However, comprehensive investigations of the influence of ground conditions on member forces have not yet been conducted. Furthermore, since these temporary structures are generally not designed with seismic considerations, they may suffer damage during earthquakes depending on the soil conditions. Accordingly, this study conducted a comprehensive parametric numerical investigation to evaluate how differences in soil type, such as sandy and cohesive soils, and loading conditions during excavation and earthquake loading affect the internal forces in the supporting members. Excavation analyses using PLAXIS 3D confirmed that as the soil strength parameters (cohesion and internal friction angle) decreased, the demand on the supporting members increased and larger internal forces developed. Dynamic analyses using LIQCA 3D revealed complex behavior in which (i) earth pressure acting on the wall generated compressive forces in the struts, (ii) lateral deformation of the excavation face reduced axial forces in the struts, and (iii) when the ground liquefied, it exhibited a vibration-isolation effect, and the vibration components generated in the structural members became smaller. Full article

Plate–monopile hybrid foundations, as a potential alternative to monopiles, have demonstrated promising potential in enhancing load-bearing capacity and structural stability. To investigate its load transfer mechanisms and pile–soil interaction in clay, numerical models are developed under varying undrained shear strength (Su), pile diameter (D), and plate-to-pile diameter ratio (R). Through comparative analyses within different parameters configurations, the load-bearing capacity, pile deflection, bending moment and shear force distributions are systematically examined. The results indicate that: (1) Su, D and R are all positively correlated with the load-bearing capacity of the hybrid foundation, which can be expressed as the superposition of the monopile capacity and a quadratic function of R; (2) with increasing R, load transfer shifts from deep to shallow soil, accompanied by an upward pivot shift; increasing D causes a downward shift, more pronounced in weak soils; (3) for small-diameter hybrid foundation, the bending moment decreases progressively with increasing R, while for large-diameter, a stage-dependent response is observed, characterised by local moment concentration near the mudline within a certain range of R; (4) the shear force exhibits a double-peak pattern; increasing R strengthens the shallow peak and weakens the deep one, while increasing D localises the distribution near the mudline. Full article