Search Results (1,410)

Frictional energy piles are a more desirable form of shallow geothermal energy utilization. A pure friction pile condition cannot be achieved in field tests. In this study, foam was placed beneath the model pile tip to weaken the end-bearing resistance. The effects of different cyclic temperature patterns (including cyclic path, external load, and variable temperature duration) on the bearing characteristics of pure friction energy piles are investigated by conducting model tests in a self-designed model box, and the variation patterns of pile stress–strain and pile-top displacement are measured. The results show the following: (1) Under no load, the displacement of the pile top changes with temperature; each round of temperature change produces a partial irrecoverable displacement, and the pile maintains a raised state at the end of both rounds with no stress accumulation. (2) Under the combined action of working load and cyclic temperature, the pile strain reaches its peak and then partially rebounds. Thermal stress accumulates progressively with increasing cycle numbers, and after the cycling ends, an irrecoverable settlement displacement (0.52% D) remains at the pile top and continues to increase. (3) The temperature cycle caused the soil volume to shrink and decreased the shear strength of the pile–soil interface, resulting in a decrease in the ultimate bearing capacity of the test pile compared to the initial state. Full article

Road networks providing access to forest stands, including integral parts such as timber yards, are subjected to significant loads from timber-transporting vehicles. These loads act on the road surfaces, causing them to deform. This study measured and compared the extent of deformation at two timber yards in the mountain forests of southern Poland in the Western Carpathians. These surfaces were constructed as: crushed stone (timber yard in the Ustroń Forest District) and earth (Forest Experimental Station of the University of Agriculture in Kraków). The measurements were carried out using photogrammetric techniques based on aerial surveys by an unmanned aerial vehicle. The measurements were based on networks of reference points with coordinates in local coordinate systems. During the period between the flights, timber was being stored, handled and transported at both sites. The forest administration provided data on the volume of timber delivered to and removed from the storage yard, as well as basic information on the transport vehicles. Soil samples were taken from the surface of both storage yards for laboratory analysis to illustrate working conditions—the soil type, current moisture content, organic matter content and filtration coefficient (from the soil particle size distribution curve) were determined. Digital terrestrial model (DTM) rasters obtained from both aerial surveys at each storage yard were used to calculate differential rasters, which were analysed by plotting cross-sections at selected locations and directions and by calculating the volume of changes in surface geometry between the survey dates. The observed depths of ruts reach 0.4 m at the Ustroń storage yard and 0.5 m at the LZD storage yard, whilst changes involving the displacement of soil from the ruts above the previous surface level are 0.3 m at the Ustroń storage yard and 0.4 m at the LZD storage yard. Greater deformation was observed on the earth surface (with a high organic content and poorer drainage) than on the crushed stone surface, even though the latter was covered by an uncleared layer of mud and waste left over from timber handling. Given the two-site, single-cycle design of this study, this pattern is consistent with—but cannot on its own confirm—a stabilising effect of surface reinforcement; differences in soil moisture, organic content and observation period between the two sites may also have contributed and could not be separated from the effect of surface type alone. Full article

The fate of heavy metals in agricultural soils is governed by organo-mineral–microbial interactions, which predictive models often fail to capture. The competitive sorption mechanisms of Cd(II) and Cu(II) on montmorillonite/kaolinite composites (Mont/Kao) functionalized with humic acid (HA) and Pseudomonas putida (P. p), a model system representative of contaminated agricultural soils, were investigated. Batch experiments, XRD, FTIR, and thermodynamic analysis reveal that metal retention is a non-additive function of competing interfacial processes. Bacterial biomass dominated sorption, accounting for >50% of total metal uptake, with capacity ranked as: P. p > Mont/Kao-P. p > Mont/Kao-HA-P. p > Mont/Kao-HA > Mont/Kao. Humic acid exerts a dual, concentration-dependent role: Low levels enhanced adsorption via mineral dispersion, while high levels induced surface masking, suppressing bacterial binding sites. Competition was highly asymmetric: Cd(II) reduced Cu(II) maximum adsorption capacity by 75.5% in the Mont/Kao-HA system by preferentially occupying montmorillonite interlayer sites, whereas Cu(II) inhibited Cd(II) below pH 6. Single-metal sorption was characterized by positive ΔS° (32.96–58.89 J·mol⁻¹·K⁻¹), indicative of inner-sphere complexation, while negative ΔS° under competitive conditions signals a transition to outer-sphere complexation. This work provides mechanistic insights into site masking, competitive displacement, and ternary cation bridging controlling metal immobilization in organo-mineral assemblages. Full article

Polypropylene (PP) fiber-reinforced soil slopes undergo progressive resistance degradation under wet–dry cycling (WDC), while stochastic seismic loading introduces additional uncertainty, challenging deterministic seismic assessment. This study develops a time-dependent seismic reliability framework integrating the probability density evolution method and the equivalent extreme value event method. The cohesion and internal friction angle of unreinforced soil measured at different WDC states are represented as cross-correlated lognormal random fields and combined with random fiber configurations and weighted nonstationary stochastic ground motions in a nonlinear dynamic model. The main contribution is a unified uncertainty-propagation scheme that incorporates experimentally characterized WDC degradation and multiple uncertainty sources into the evolution of response probability and multilevel first-passage reliability. With increasing WDC number and PGA, the extreme displacement distributions shift toward larger values, accompanied by increased response dispersion, tail risk, and reliability loss. The reliability evolution exhibits three stages, namely initial stability, rapid degradation, and residual convergence, during the 70 s excitation. PP fiber reinforcement improves reliability, although the marginal gain becomes limited when the fiber content exceeds 0.15% under the present numerical conditions. The proposed framework provides a probabilistic basis for the seismic assessment and deformation control of PP fiber-reinforced soil slopes at different WDC degradation states. Full article

This paper proposes an annular suction caisson specifically designed to reinforce in-service monopiles and upgrade existing offshore wind farms to accommodate larger-capacity wind turbines. During penetration of the annular suction caisson into clay, the existing monopile restricts the inward migration of soil into the internal space of the caisson, promoting upward soil displacement and consequently increasing the height of the soil plug formed inside the caisson. In addition, the strain-softening behavior causes varying degrees of strength degradation in the clay along the caisson wall. The softened zones extend approximately one caisson wall thickness on the inner side and 1.2 times the wall thickness on the outer side of the caisson. Both effects should be considered for accurately predicting the penetration resistance of annular suction caissons. Therefore, three-dimensional large-deformation finite element analyses were performed to investigate the penetration behavior of annular suction caissons in strain-softening clay. A comprehensive parametric study was conducted to quantify the soil plug heave and overall penetration resistance. Meanwhile, the soil flow mechanism at the caisson tip, the evolution of clay strength along the caisson wall, and the formation characteristics of the internal soil plug were systematically examined. Based on the numerical results, a theoretical approach was developed to evaluate the penetration resistance of annular suction caissons. Full article

This study presents a performance-based forensic investigation of the Tanada wall, a geosynthetic reinforced soil wall with a full-height rigid facing that experienced strong shaking during the 1995 Hyogoken Nambu earthquake in Japan. The analytical framework integrates a compiled soil stress–displacement dataset, limit equilibrium constraints, displacement-based back analysis, reconstruction of the displacement (Δ_3h)–seismic inertial coefficient (k_h) curve, and systematic parameter sensitivity evaluation. The displacement-based seismic resistance curves developed using representative soil parameters show that the Tanada wall maintains strong seismic resistance up to HPGA ≈ 0.7–0.8 g, with displacement trends that remain physically consistent across three logarithmic cycles. Sensitivity analyses demonstrate that only three parameters—the soil stiffness number K, peak friction angle φ_peak, and the initial pullout stiffness number K_t—produce variations of approximately ±0.8–1.5 × 10⁻³ m in the final displacement Δ_3h. All remaining soil, reinforcement, and facing parameters contribute only minor variations on the order of a few 10⁻⁴ m. These findings show that the force-equilibrium-based finite displacement method (FFDM), supported by laboratory evidence and displacement-based inference, provides a rigorous and physically grounded methodology for forensic evaluation of reinforced soil structures. Full article

Accurate prediction of excavation-induced soil rebound is critical for intelligent foundation pit construction. The existence of engineering piles in the foundation pit will affect soil rebound at the bottom of the pit caused by excavation. Based on the layer-wise summation method, the Mindlin solution and the existing calculation methods of pile-soil displacement, the rebound deformation of the soil at the bottom of the pit caused by the excavation unloading of the foundation pit was studied and an automated computation algorithm for calculating soil rebound under the existence of an engineering pile was proposed. Finally, the calculation results of the proposed method and the finite element simulation results were compared and analyzed with an example of engineering. The results show that for the rebound curve of the foundation pit bottom, when there are no engineering piles, it presents a smooth ‘convex’ shape; when engineering piles exist, it presents a fluctuant ‘wave’ shape. The rebound of the soil around the engineering piles is significantly lower than that of the neighboring soil, with the smallest drop in the edge area of the foundation pit and the largest drop in the central area, and the maximum reduced rebound can reach about 20% at most. The ability of piles to limit soil rebound is greatly related to the pile spacing and pile diameter. It is necessary to correctly consider the existence of engineering piles in the rebound calculation of the soil at the bottom of the foundation pit, and the results obtained by the proposed method in the paper are in good agreement with the simulated rebound values. The method proposed in this paper can effectively predict the rebound deformation of the foundation pit. Full article

Expansive soils are rich in hydrophilic clay minerals, and repeated wetting–drying cycles can induce deformation that threatens infrastructure safety. Therefore, accurate monitoring of soil moisture (SM) dynamics is essential for understanding hydro-mechanical processes and assessing related geohazards. In this study, spaceborne Global Navigation Satellite System Reflectometry (GNSS-R) is applied to expansive SM monitoring, and an Attention-Enhanced Spatio-Temporal Graph Convolution Network (ASTGCNet) is proposed for SM retrieval. The Texas coastal region, where Beaumont clay is widely distributed, was selected as the study area. The ASTGCNet-derived SM showed consistency with the Soil Moisture Active Passive (SMAP) reference product, with an overall correlation coefficient of 0.92, an RMSE of 0.035 m³/m³, and a bias of 0.006 m³/m³. Validation against in situ observations showed that ASTGCNet provided more accurate SM estimates than the Cyclone Global Navigation Satellite System (CYGNSS) L3 SM product. Extended triple collocation analysis further indicated that ASTGCNet achieved the lowest standard deviation of 0.020 m³/m³ and the highest signal-to-noise ratio of 7.33. Compared with non-expansive soils, expansive soils exhibited stronger water absorption and moisture retention behavior. By integrating GNSS vertical displacement observations, the retrieved SM revealed a nonlinear SM–deformation response that was mainly observed in shallow expansive soils. Drying-induced SM decreases corresponded to pronounced subsidence, while subsequent wetting led to ground rebound; this behavior was not clearly observed in non-expansive soils. This study demonstrates the potential of GNSS-R for expansive SM monitoring and provides new insights into the coupling between SM dynamics and deformation. Full article

Local scour reduces the lateral restraint provided by surrounding soil and may amplify the impact-induced response of bridge foundations. This study investigates the response of a lattice-shaped diaphragm wall (LSDW) foundation–soil system under predefined local-scour conditions using a three-dimensional explicit finite element model and a nominally rigid steel impactor. A 1:30 reduced-scale configuration was analyzed at impact velocities of 2, 3, and 4 m/s and scour depths of 0, 200, 300, and 400 mm. Increasing impact velocity generally increased wall displacement, velocity, and elastic principal-stress demand, whereas deeper scour reduced the remaining embedment and the restraint provided by the surrounding soil. Relative to the corresponding unscoured conditions, the normalized peak wall-top displacement ratios were 1.28–1.38, 2.01–3.66, and 3.28–5.45 for scour depths of 200, 300, and 400 mm, respectively. The velocity distribution showed an increasingly pronounced rotational contribution as the remaining embedment decreased. Case 9 produced the largest overall response, with a peak wall-top displacement of 398.7 mm and a peak wall-top velocity of 5.2 m/s. Because direct physical validation was unavailable, the results should be interpreted as comparative model-scale trends rather than validated prototype predictions. Full article

Frozen soil on alpine slopes is influenced by inclination and aspect-induced differential solar radiation effects, resulting in non-uniform temperature fields and inclined layered ice lenses that enhance anisotropy and degrade mechanical properties. This study investigates the deformation and strength responses of frozen soil under different temperature-gradient magnitudes and orientations and ice-lens conditions. A stress–strain constitutive model incorporating the magnitude and orientation of the temperature gradient is established. In addition, an equal-scale discrete element model based on the parallel-bond contact model is developed and calibrated against the laboratory results. The numerical specimen is divided into 13 layers, and temperature-dependent interparticle bond properties are assigned layer by layer to reproduce the prescribed magnitude and orientation of the temperature gradient. Results show that the orientation of the temperature gradient significantly alters the mechanical response and failure mode. As the inclination angle increases, the failure mode transitions from compressive dilatancy to combined dilatancy–shear failure and ultimately to shear-dominated failure. At −10 °C, increasing the inclination angle from 0° to 30° reduces the compressive strength by 44.48%. The elastic modulus also decreases with increasing inclination, with a maximum inclination-induced difference of 111.98 kPa. Moreover, the presence of an ice lens further reduces specimen stiffness, and the elastic-modulus difference between ice-lens-bearing and ice-lens-free specimens increases from 5.57 kPa at −1 °C to 75.72 kPa at −10 °C. The DEM results show that particles at the top and bottom of the specimen primarily undergo vertical displacement, whereas particles in the middle region exhibit dominant horizontal displacement, forming an X-shaped shear band. The inclined temperature gradient produces a heterogeneous distribution of interparticle bond strength within each horizontal layer. As inclination increases, the shear band evolves from symmetric to asymmetric; particle displacements on the side toward which the temperature gradient points are larger than those on the opposite side, revealing the microscopic origins of macroscopic mechanical behavior. Full article

The dynamic response analysis of saturated porous media is frequently required in engineering practice, which necessitates handy and accurate analysis tools. In view of this demand, the present paper provides a simple user-defined element (UEL) to incorporate the u-w formulation of Biot’s theory for wave propagation in saturated porous media into the general finite element program ABAQUS. As an essential supplement to the UEL, an artificial boundary condition named the multi-transmitting formula (MTF) is embedded into ABAQUS to simulate the semi-infinite far field. The eight-node linear interpolation functions are applied to the 3D fields of the solid skeleton (u) and relative pore-fluid (w) displacements, respectively. The time marching of the resulting finite element equations is achieved by the implicit Hilber–Hughes–Taylor scheme. The details of the implementation and utilization of the UEL and MTF are presented in a detailed tutorial fashion. The developed UEL and MTF are then validated by simulations of six saturated soil dynamic problems, which span a wide range of analysis scenarios. It is demonstrated that the coupled UEL and MTF are effective tools for researchers and engineers to analyze many problems pertaining to the dynamics of saturated porous media. 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

Accurate estimation of terrestrial water storage change (TWSC) remains challenging in regions where hydrological variability interacts with complex geological conditions and intensive human activities. Taking the Loess Plateau (LP) in the middle Yellow River region as a case study, this work integrates GLDAS simulations, GRACE observations, GNSS vertical-displacement records, a joint GNSS–GRACE inversion, and meteorological data for 2013–2024 to investigate regional TWS variability and model-dependent discrepancies. The results show that GLDAS, GRACE, GNSS, and the joint solution exhibit distinct temporal trends and spatial patterns. GRACE indicates a stronger long-term depletion signal, whereas GNSS-derived equivalent water height (EWH), which relies on the assumption of elastic surface loading, shows a weaker trend but stronger seasonal variability. This discrepancy suggests that GNSS-based inversion over the LP may be affected by non-elastic or non-loading deformation processes, such as wetting-induced loess collapse, aquifer compaction, mining-related subsidence, and other near-surface effects. In contrast, GRACE may include non-TWS mass redistribution associated with soil erosion and mineral exploitation. The joint solution is more consistent with the GLDAS-derived hydrological model benchmark than either single geodetic estimate, but this agreement should not be interpreted as direct proof of higher accuracy or complete removal of non-hydrological effects. Overall, this study highlights the need to diagnose model-dependent discrepancies, effective spatial resolution, and non-loading deformation when applying GRACE- and GNSS-based approaches to TWSC estimation in geologically and anthropogenically complex regions. Full article

Ice lenses in natural frozen soils commonly exhibit inclined and heterogeneous distributions, and their spatial morphology significantly influences the mechanical behavior of frozen soils. To investigate the coupled regulatory mechanism of ice lens inclination angle and thickness on the mechanical properties of frozen silty clay, specimens containing artificial single-layer ice lenses with varying inclination angles (0°, 10°, 20°, 30°) and thicknesses (5 mm, 15 mm) were prepared under constant temperature, water content, and loading rate conditions. Low-temperature uniaxial compression tests were conducted, and the results were systematically analyzed in conjunction with discrete element method (DEM) simulations and a modified Duncan–Chang model. The results indicate that increasing the ice lens inclination angle leads to a nonlinear reduction in the deviatoric stress at 15% axial strain, with the failure mode transitioning from compression-induced bulging to shear sliding dominance. When the ice lens thickness increased from 5 mm to 15 mm, the deviatoric stress at 15% axial strain further decreased across all inclination angles, accompanied by a reduction in the composite modulus. The response surface prediction formulas for parameters a and b, established based on experimental data, effectively describe the stress–strain relationships. DEM simulations reveal, at the mesoscale, the asymmetric displacement field and shear band evolution mechanisms governed by inclined ice layers, with bond breakage accelerating as the inclination angle increases. This study clarifies the coupled effects of ice lens spatial configuration and confining pressure on the mechanical response of frozen soils, providing a theoretical reference for bearing capacity assessment of frozen ground containing inclined ice lenses. Full article

The pressuremeter test (PMT) measures in situ soil properties under the original stress state with minimal disturbance. However, interpreting PMT data for constitutive parameters remains reliant on empirical correlations, and a key challenge is the poorly understood size effect arising from the equipment dimensions. This study aims to systematically quantify such size effects to provide a scientific basis for optimizing the design of laboratory PMTs. A series of 36 PMT simulations were performed using the finite element method (FEM), incorporating the Duncan–Chang E-B hyperbolic model. Six cylindrical soil models of diameters ranging from 0.6 m to 2.4 m were established for both sand and clay, under three overburden pressures (200 kPa, 1000 kPa and 3000 kPa). The radial stress, strain distributions and borehole wall displacement were systematically analyzed. The analysis reveals that the size effect originates from the truncation of the radial strain integration path. In all cases, borehole wall displacement increases with model diameter, characterized by a steep rise for diameters below 1.2 m and a plateau for those above 1.2 m. Although clay produces larger displacements than sand, and higher stress produces larger displacements than lower stress, the identified pattern remains robust. Considering both the displacement–diameter relationship and practical cost constraints, an optimal equipment diameter of 1.2 m is recommended. Full article