Search Results (115)

The excavation of deep shafts using Vertical Shaft Sinking Machine (VSM) technology in stratified soft soils involves complex soil-structure interaction (SSI) mechanisms that are often oversimplified by conventional numerical approaches. This study develops a robust three-dimensional numerical framework to investigate ground deformation induced by VSM operations, explicitly incorporating the phased construction sequence, segmental lining installation, and site-specific stratigraphy. The model is calibrated and validated against high-resolution field monitoring data, employing a prediction envelope approach and statistical performance metrics (RMSE and $R^2$). The results suggest that ground response during VSM excavation is predominantly stiffness-controlled under the investigated conditions. Mobilized shear stresses remain significantly below the available soil capacity, indicating that deformation under serviceability conditions is driven by progressive strain accumulation. Horizontal displacement profiles suggest a relatively stable depth of influence, indicating that the excavation process amplifies deformations within a pre-established domain without significant deep-seated propagation. Sensitivity analyses indicate soil stiffness modules ($E_{50},E_{oed},E_{ur})$ and the SSI interface factor ($R_{inter}$) as the primary drivers of deformation magnitude. Furthermore, stratigraphic contrasts specifically clay-sand sequences, act as a mechanical filter, concentrating strains in soft layers while limiting vertical propagation through stiffer strata. The proposed framework provides a mechanically coherent basis for serviceability-oriented design, deformation prediction, and risk-mitigation strategies for mechanized shafts in saturated soft ground. Full article

Tunnel construction in soft soil environments involves significant geological and hydraulic uncertainty, particularly where permeable sandy interlayers within soft clay are prone to seepage-induced instability and excessive settlement. Although hydraulic–mechanical coupling is widely recognized, the spatial variability of key soil parameters (e.g., permeability and elastic modulus) is often inadequately represented, limiting quantitative evaluation of heterogeneous ground effects on construction-induced deformation. In this study, statistical analyses of site investigation and monitoring data are conducted to characterize parameter distributions and transverse settlement trough morphology, supporting model validation. A fluid–solid hydro-mechanical coupled numerical model in ABAQUS demonstrates that groundwater flow increases maximum surface settlement from 3.18 cm to 3.58 cm, confirming the significance of hydraulic coupling. To quantify spatial variability effects, a stochastic finite element framework based on random field theory is developed, showing that variations in vertical correlation length influence both the mean and dispersion of maximum settlement. Specifically, under a settlement control threshold of 40 mm, the failure probability decreases from 24.21% to 1.01% as the vertical correlation length increases from 1.5 m to 6 m. Finally, an engineering-oriented risk assessment framework is established using settlement trough area as the core loss indicator; its lognormal distribution is verified, and failure probability and reliability indices are integrated with code-based thresholds to evaluate construction risk under different scenarios, with the resulting risk levels ranging from Relatively High (Level III) to Moderate (Level II). Full article

The full-flow T-bar penetrometer has been extensively employed in centrifuge model tests and offshore site investigations to measure the undrained shear strength of soft clays. A rigorous correlation between T-bar resistance and undrained shear strength relies heavily on the elucidation of the resistance factor N_t, which has been widely pursued utilizing classical plasticity according to a full-flow mechanism. However, the adoption of a constant resistance factor N_t in the absence of a full-flow mechanism at shallow penetration due to the cavity above the T-bar cylinder has been identified to underestimate the soil strength. Thus, to accurately interpret T-bar penetration data, this paper presents theoretical investigations into the resistance factor of the T-bar penetrometer considering the cavity effect. A generalized theoretical solution of the resistance factor N_t is deduced in terms of roughness factor α at the T-bar-soil interface and sidewall inclination δ of the cavity, which will degenerate to the well-known plasticity solutions of Randolph and Houlsby (1984) when the cavity vanishes. Theoretical results show that the resistance factor N_t increases with increasing roughness factor α, but decreases with increasing sidewall inclinations δ. Finally, the rationality of the proposed failure mechanism and theoretical results are verified against finite element limit analysis (FELA) conducted in this study, as well as the numerical results and theoretical solutions in the existing literature. Full article

Pinus clausa var. clausa (Chapm. ex Engelm.) Vasey ex Sarg., sand pine, is the dominant tree of biorich but ecologically compromised Southeast Florida scrub. Scrub habitats and P. clausa have dwindled due to habitat reduction and fragmentation, regional development, and fire suppression. The purpose of the present article was to seek correlates of P. clausa establishment under present unnatural development-impacted conditions using 428 field measurements at four sites to determine spatial positioning preferences relative to vegetation edges, then adding 120 measurements at a single site aimed at evaluating several potential predictors of P. clausa establishment. Potential establishment predictors were adjacency to other woody plants, depth to hard sand horizon, seed tree distance and direction, light-intensity, soil-core color, soil pH and soil surface firmness. Comparing frequency distributions of juvenile P. clausa locations with frequency distributions of random spots within the same perimeters, juvenile pines tended toward adjacency to other woody plants (chi² p < 0.0001), toward shallow hard horizons (Kolmogorov–Smirnov p = 0.0006), toward soft soil surfaces (K–S p = 0.007), and toward proximity to seed trees (K–S p = 0.004). Additionally, juvenile P. clausa were often clustered under groves of Quercus geminata Small with comparatively thin canopies. Bayesian logistic regression showed adjacency to woody plants as a strong predictor of P. clausa establishment. When alongside other plants, P. clausa establishment was mostly on the north or east side of neighboring plant edges. Overall conclusions were that juvenile Pinus clausa in SE Florida scrub fragments is sensitive to positioning relative to other woody plants, and is associated with soil surface softness, soil depth to hard horizon, and light levels, except as seedlings. Full article

More and more urban underpass tunnels are being constructed to alleviate traffic congestion; however, for this type of underground structure, the soil–structure interaction mechanisms under earthquake loading remain unclear, and dedicated advice and guidance for their seismic design are still lacking. This paper endeavors to investigate the dynamic interaction mechanisms of an underpass tunnel and surrounding soft ground using the finite element (FE) method. Firstly, the accuracy of the FE model in reproducing seismic responses of the layered half-space is validated by comparison with results of equivalent linear one-dimensional site response. Then, the dynamic response characteristics of 3D boat-shaped excavation are analyzed to determine the influence of potential local site amplification on the underpass tunnel. Finally, seismic behaviors of open and buried sections of the underpass tunnel are investigated in detail. The results show that under high-intensity rare earthquakes, severe damage occurs at the ceiling slab near the longitudinal beam and at the base of the side wall of the tunnel’s buried section; seismic underpass–site interactions might be influenced the most by the local topography effect of the 3D boat-shaped excavation, as well as a sudden stiffness change between the open and buried sections. Full article

This study presents a site-specific calibration of the ratio between S-wave and P-wave peak ground acceleration (PGA) for use in low-cost, on-site earthquake early warning (EEWS) systems in Iași, Romania. A dataset of 25 intermediate-depth Vrancea earthquakes (Mw 4.1–5.7; epicentral distances 150–210 km) was analyzed. PGA values were extracted for the P- and S-wave windows on both horizontal components and combined using geometric means. The resulting S/P amplitude ratios yield a median value of k_S/P = 6.19 and a logarithmic standard deviation of σlog₁₀ = 0.31, corresponding to a multiplicative uncertainty factor of approximately ×2. These results indicate that S-wave amplitudes are typically six times larger than P-wave amplitudes at this site, consistent with soft-soil amplification observed in comparable stations in Japan and Italy. The calibrated ratio can be used as a site-specific input for future MEMS-based on-site EEW implementations to estimate the expected S-wave PGA immediately after P-wave detection, with the observed S–P delays in Iași indicating a typical available warning window of 20–22 s. Full article

Limitations of the cone penetration test, especially to accurately determine undrained shear strength (S_u) in soft soil deposits with high in situ stresses, have motivated the development of alternative devices, such as the T-bar and ball penetration tests, commonly referred to as flow penetrometers. These devices can estimate, in a single test, both the undrained shear strength (S_u) and the remolded strength (S_ur). When equipped with pore pressure sensors, they also provide valuable information on soil stratigraphy and consolidation parameters, making them versatile tools for characterizing soft soils. This study presents the development of two flow penetrometers, piezoball and piezo-T, highlighting relevant aspects of their design and calibration, followed by experimental campaigns conducted in two Brazilian clay deposits (Tubarão/SC and Sarapuí/RJ). Field tests enabled a direct comparison between the flow penetrometers and conventional methods, both in terms of S_u and S_ur. The investigation also examined the coefficient of consolidation of the soft soils. The results demonstrate good repeatability and consistent values for the bearing capacity factors (N_b and N_t) and remolded behavior (N_b-rem and N_t-rem). Regarding the performance of the pore pressure transducers, the piezoball test demonstrated good performance in pore pressure measurements and derived coefficients of consolidation. In contrast, despite the proposed design modifications, the piezo-T exhibited instability in the readings. Although the findings are derived from specific sites, the discussion is framed in light of the ranges reported internationally, highlighting potential local implications and reinforcing the need to expand robust geotechnical databases to support future applications. Full article

The geological complexity of Java Island, Indonesia, has resulted in the extensive distribution of very soft clay soils, posing significant challenges to geotechnical design and construction. A reliable estimation of the geotechnical properties of these soils is therefore essential to address these challenges and ensure the safety and sustainability of construction projects. The cone penetration test with pore pressure measurement (CPTu) is a reliable in situ test for soil characterization, providing a continuous shear strength profile. However, the determination of a representative cone bearing factor ($N_{kt}$) to estimate undrained shear strength ($S_u$) is critical for geotechnical design. Although several studies on CPTu have been conducted in Indonesia, there has been a lack of emphasis on establishing $N_{kt}$ values for local soft, high-plasticity clays in Indonesia. This study aims to fill this gap in the literature by proposing updated correlations for $N_{kt}$ specific to the soft, high-plasticity clays of Java, Indonesia, derived from the statistical analysis of combined field and laboratory data obtained from two representative sites in Western Java. These sites correspond to a coastal plain deposit in Central-North Jakarta and an alluvial deposit in Gedebage, Bandung. A comprehensive database was compiled, consisting of 20 CPTu boreholes, 84 depth points of vane shear test (VST), 29 samples of consolidated undrained (CU) triaxial tests, 26 samples of unconsolidated undrained (UU) triaxial tests, and 18 standard penetration test (SPT) boreholes. The results indicate that the representative $N_{kt}$ value for these soft, high-plasticity clays in the investigated sites in Western Java ranges from 14 to 16. A refined empirical correlation between $N_{kt}$ and the pore pressure ratio (B_q) is proposed, demonstrating consistent trends with recent data. Additionally, a reasonable correlation between the undrained modulus ($E_u$) and undrained shear strength of $E_u$ = 276–323 $S_u$ was identified, enabling the derivation of a continuous profile of the undrained modulus from CPTu data. This study also further highlighted the absence of significant relationships between $N_{kt}$ and other parameters such as OCR, PI, and NSPT. These findings provide practical insight and a regionally calibrated reference that can be useful for engineers working in similar soft, high-plasticity clay environments with characteristics comparable to the investigated sites in Western Java. Full article

Earthquake Early Warning (EEW) systems based on on-site measurements enable ultra-rapid alerts by exploiting the time gap between the arrival of P-waves and the subsequent damaging S-waves. A central challenge is the reliable estimation of impending ground motion using only the earliest portion of the signal. This study investigates a site-specific methodology based on the S/P amplitude ratio for near-real-time seismic acceleration estimation at the Iași stations, Romania, in a region dominated by Vrancea intermediate-depth seismicity. Using 50 strong-motion records from the European Strong-Motion (ESM) database, a local calibration coefficient of k = PGA_S/PGA_P = 6.2 was derived for the Iași area, consistent with its soft-soil conditions and with values reported for comparable sedimentary environments worldwide. A regional analysis confirms that the S/P ratio is primarily governed by local site effects, requiring station-level calibration. The methodology was experimentally validated through shaking-table tests using real P-wave recordings. Predicted S-wave peak ground accelerations exhibit no systematic bias, with a median relative error of +2.0% and dispersion consistent with the intrinsic log-normal variability of the S/P ratio. The results demonstrate that a locally calibrated S/P ratio provides a robust and physically grounded basis for rapid seismic acceleration estimation in on-site EEW systems. Full article

In order to identify an efficient and environmentally friendly washing agent for heavy metal-contaminated soil, this study selected seven natural amino acids—arginine (Arg), alanine (Ala), glycine (Gly), cysteine (Cys), lysine (Lys), threonine (Thr), and glutamic acid (Glu)—based on their water solubility, effectiveness, and functional group characteristics. According to the removal efficiencies for zinc (Zn), lead (Pb), and cadmium (Cd), Cys, which contains a specific sulfhydryl group (-SH), was chosen as the target leaching agent for the remediation of composite-contaminated soil. The optimal process conditions were determined as follows: 0.02 mol/L of cysteine concentration, liquid-to-soil ratio of 20:1 (mL/g), 10 min of ultrasonic time, and pH = 8.0. The order of removal efficiency was Pb (40.8%) > Zn (21.6%) > Cd (19.9%). The leaching process selective effects on the speciation fractions of Zn, Pb, and Cd in the soil, and these differences can be explained by the hard–soft acid–base theory and the strength of coordination between the metals and cysteine. Mechanism analysis revealed that soil washing essentially achieves selective extraction of the target metal through strong chemical interactions between functional groups of cysteine and active metal sites of secondary minerals in the soil. Cysteine is a green remediation agent with high selectivity and environmental compatibility for contaminated soil. Its application requires precise design and risk assessment based on the chemical properties of the target metals, while ensuring the sustainability of the soil to maintain the ecological functions and long-term health of the remediated soil. Full article

Pile foundations are critical load-bearing components in bridge structures, particularly in soft, high-moisture soils susceptible to external disturbances. This study investigated the impact of large-scale soil excavation on the stability of adjacent pile foundations through comprehensive field monitoring of a newly constructed bridge during both the bridge construction and channel excavation phases. The close proximity of the excavation site to the pile caps facilitated a detailed assessment of soil–structure interaction. The results indicate that the pile axial force peaked at the pile head and decreased progressively with depth, consistent with the load transfer mechanism of friction piles. Notably, a distinct variation in axial force was observed at the bedrock interface, attributed to reduced relative displacement between the pile and the surrounding soil. Furthermore, channel water filling raised the local groundwater table, which increased the buoyancy and reduced negative skin friction, thereby decreasing the pile axial force. The study also highlighted the sensitivity of pile deformation in soft soil to unbalanced earth pressure. Asymmetric excavation and surface surcharge loading were identified as critical factors compromising pile stability and overall structural safety. These findings provide valuable insights for construction practices and offer effective strategies to mitigate adverse excavation effects, ensuring long-term structural stability. Full article

Subsurface deposition determines whether soils, aquifers, or ocean sediment represent a sink or temporary reservoir for microplastics. Deposition is generally studied by applying the Smoluchowski–Levich equation to determine a particle’s sticking efficiency, which relates the number of particles filtered by sediment to the probability of attachment occurring from an interaction between particles and sediment. Sticking efficiency is typically measured using column experiments or estimated from theory using the Interaction Force Boundary Layer (IFBL) model. However, there is generally a large discrepancy (orders of magnitude) between the values predicted from IFBL theory and the experimental column measurements. One way to bridge this gap is to directly measure a microparticle’s interaction forces using Atomic Force Microscopy (AFM). Herein, an AFM method is presented to measure sticking efficiency for a model polystyrene microparticle (2 μm) on a model geomaterial surface (glass or quartz) in environmentally relevant, synthetic freshwaters of varying ionic strength (de-ionized water, soft water, hard water). These data, collected over nanometer length scales, are compared to sticking efficiencies determined through traditional approaches. Force measurement results show that AFM can detect extremely low sticking efficiencies, surpassing the sensitivity of column studies. These data also demonstrate that the 75th to 95th percentile, rather than the mean or median force values, provides a better approximation to values measured in model column experiments or field settings. This variability of the methods provides insight into the fundamental mechanics of microplastic deposition and suggests AFM is isolating the physicochemical interactions, while column experiments also include physical interactions like straining. Advantages of AFM over traditional column/field experiments include high throughput, small volumes, and speed of data collection. For example, at a ramp rate of 1 Hz, 60 sticking efficiency measurements could be made in only a minute. Compared to column or field experiments, the AFM requires much less liquid (μL volume) making it effortless to examine the impact of solution chemistry (temperature, pH, ionic strength, valency of dissolved ions, presence of organics, etc.). Potential limitations of this AFM approach are presented alongside possible solutions (e.g., baseline correction, numerical integration). If these challenges are successfully addressed, then AFM would provide a completely new approach to help elucidate which subsurface minerals represent a sink or temporary storage site for microparticles on their journey from terrestrial to oceanic environments. Full article

The 17 November 2023 M_W 6.8 earthquake located offshore of Southern Mindanao, Philippines, triggered soil liquefaction along the lowlands of the Sarangani Peninsula. Detailed mapping, geomorphological interpretations, geophysical surveys, comparison with predictive models, and grain size analysis were conducted to obtain a comprehensive understanding of the earthquake parameters and subsurface conditions that permitted liquefaction. Soil liquefaction manifested as sediment and water vents, fissures, lateral spreads, and ground deformation, mainly along landforms with shallow groundwater levels such as river deltas, fills, floodplains, and beaches. In populated areas, ground failure due to liquefaction also damaged some buildings. All these impacts fall within the boundaries of the available liquefaction hazard maps for Sarangani Peninsula and the predictive empirical equations generated by various authors. Simulated peak ground acceleration values also indicate that sufficient ground shaking was generated for the soil to liquefy. Refraction microtremor (ReMi) surveys reveal shear wave velocities ranging from 121 to 215 m/s, which infer the presence of soft and stiff soils beneath the surface, promoting the sites’ potential to liquefy. Grain size analyses of sediment ejecta confirm the presence of these liquefiable sediments from the subsurface, with grain sizes ranging from silt to medium sand. The results of three-component microtremor (3CMt) surveys also show varying sediment thicknesses, which are consistent with the thickness of soft sediment layers inferred by ReMi surveys. The information resulting from this study may be useful for researchers, planners, and engineers for liquefaction hazard assessment and mitigation, especially in the Sarangani Peninsula. Full article

Ground settlement is a multifaceted geological phenomenon driven by natural and man-made forces, posing a significant impediment to sustainable urban development. Thus, ground settlement susceptibility (GSS) mapping has emerged as a critical tool for understanding and mitigating cascading hazards in seismically active and anthropogenically modified sedimentary basins. Here, we develop an integrated framework for assessing GSS in the Pohang region, South Korea, by integrating Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR)-derived vertical land motion (VLM) data with seismological, geotechnical, and topographic parameters (i.e., peak ground acceleration (PGA), effective shear-wave velocity (V_s³⁰), site period (T_s), general amplification factor (A_F), seismic vulnerability index (K_g), soil depth, topographic slope, and landform classes) through ensemble machine learning models such as Random Forest (RF), XGBoost, and Decision Tree (DT). Analysis of 56 Sentinel-1 SLC images (2017–2023) revealed persistent subsidence concentrated in Quaternary alluvium, reclaimed coastal plains, and basin-fill deposits. Among the tested models, RF achieved the best performance and strongly agreed with field evidence of sand boils, liquefaction, and structural damage from the 2017 Pohang earthquake. The very-high-susceptibility zones exhibited mean subsidence rates of −3.21 mm/year, primarily within soft sediments (V_s³⁰ < 360 m/s) and areas of thick alluvium deposits. Integration of the optimal RF-based GSS index with regional building inventories revealed that nearly 65% of existing buildings fell within high- to very-high-susceptibility zones. The proposed framework demonstrates that integrating PSInSAR and ensemble learning provides a robust and transferable approach for quantifying ground settlement hazards and supporting risk-informed urban planning in seismically active and complex geological coastal environments. Full article

The static drill-rooted energy pile is an emerging green technology increasingly applied in coastal soft soil areas. Existing research has mainly focused on its heat transfer and bearing characteristics, while studies on its environmental impacts remain limited. Based on the Green Building Evaluation Standard and the Life Cycle Assessment method and drawing on practical energy pile projects in coastal areas, this study developed an environmental impact assessment system for energy piles. A comprehensive evaluation method was established, incorporating four indicators: muck and slurry discharge, vibration, noise, and carbon reduction benefits. Using a pilot project, field testing and theoretical analysis were conducted to assess the environmental impact of static drill-rooted energy piles. The results revealed that muck and slurry discharge is significantly lower compared to bored energy piles. Vibration levels at a site office located 30 m from the construction point were below the annoyance threshold of 0.05 g in terms of relative vibration acceleration. Noise levels dropped below the emission limit of 85 dB at a distance of 5 m. Carbon emissions during the material production stage were reduced by 22–45% compared to bored energy piles and by 12% during the construction stage. During the operation stage, compared to air-source heat pumps, electricity savings of 0.691–0.836 kWh per hour and CO₂ emission reductions of 0.471–0.57 kg per hour were achieved. Based on the comprehensive scoring of all indicators, the static drill-rooted energy pile technology received an overall rating of ‘‘excellent.’’ This study provided an evaluation framework for the environmental assessment of energy piles and contributed positively to promoting the development of green infrastructure. Full article