Search Results (807)

Large-scale excavation for pumped-storage hydropower stations (PSPSs) in mountainous areas substantially alters slope soils and accelerates ecological degradation, yet quantitative multi-indicator assessments for such projects remain limited. This study integrates field surveys, laboratory analyses, and multi-temporal remote-sensing data to evaluate the disturbance-induced evolution of soil properties at two representative PSPSs in China. Soil bulk density and porosity measurements revealed significant compaction on disturbed slope surfaces, particularly on soil-dominated slopes. Key nutrient indicators, including organic matter, alkali-hydrolysable nitrogen, available phosphorus, and available potassium, showed consistent declines relative to adjacent undisturbed habitats. A comprehensive ecological degradation indicator (EDI) was constructed using five vegetation and soil spectral indices (RVI, NDVI, SAVI, SBI, and SM) weighted through the analytic hierarchy process. Time-series EDI mapping (2019–2023) demonstrated a progressive increase in moderately to extremely degraded areas during intensive construction stages. The results highlight the strong spatial heterogeneity of disturbance effects and underscore the necessity of soil-focused restoration strategies. This integrated assessment framework provides a scientific basis for guiding near-natural restoration and long-term soil–vegetation management in PSPS infrastructure landscapes. Full article

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 R2). 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 (E50,Eoed,Eur) and the SSI interface factor (Rinter) 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

Aiming to address the problems of shield chamber blockage and poor muck discharge faced by earth pressure balance shields during tunneling in sandy strata, bentonite slurry is used for muck improvement. Using a multi-scale approach combining macro-scale experiments, micro-scale analysis, and molecular dynamics simulations, this study systematically investigates the interface interactions between particles of sandy soil in shield tunneling and the improvement mechanism of sodium-based bentonite slurry additives. Through the macroscopic experiment, the sodium bentonite slurry soil–water ratio of 1:7 and injection ratio of 25% showed the best improvement effect. After improvement, the permeability coefficient decreased by 99.72%; the cohesion of the excavated soil increased from 3.055 kPa to 11.458 kPa, representing a 275.06% increase; and the angle of internal friction decreased from 42.318° to 36.985°, a decrease of 12.60%. The improvement was significant. Through SEM, XRD, and FTIR microanalysis, it is found that bentonite slurry forms a flexible film on the surface of sandy soil. By coating sand particles, filling voids in the soil, and enhancing interparticle cohesion, it improves the properties of the soil. On the nanoscale, a Na-MMT/SiO₂ system model is established based on molecular dynamics simulations to elucidate the interactions between bentonite slurry and sand particle interfaces. The results indicate the presence of van der Waals forces and hydrogen bonds between Na-MMT and SiO₂. Interlayer water molecules form a hydrogen bond network that strengthens interfacial bonding, enabling bentonite slurry to tightly adhere to soil particle surfaces. This improves the microstructure of the soil, thereby enhancing its macroscopic properties. Full article

Given the challenges posed by high groundwater levels, thick sand layers, and strong permeability in water-rich sandy strata, cut-off walls often fail to fully isolate the hydraulic connection between the inside and outside of a foundation pit. As a result, dewatering inside the pit—especially from confined aquifers—can cause significant external groundwater drawdown and subsequent ground settlement. Using a deep excavation conducted in Xiamen as a case study, this study developed a two-dimensional hydro-mechanical coupled finite element model to systematically investigate the effects of various dewatering scenarios and soil permeability coefficients on surface settlement around the pit, and to reveal settlement patterns induced by dewatering and excavation in such strata. Field monitoring data were incorporated to validate the numerical model, ensuring accuracy and reliability. Key findings include the following: (1) Dewatering contributes to over 76% of the total settlement at each stage, with confined drawdown being the dominant factor, implying that dewatering optimization should take priority over controlling excavation rate. (2) Under confined dewatering, the settlement influence zone extends beyond 80 m, far exceeding the extension caused by excavation alone; thus, monitoring and protection ranges must be adjusted dynamically. (3) The horizontal permeability of sand shows a nonlinear positive correlation with settlement, and this sensitivity grows with depth, highlighting the need for accurate permeability determination and stricter controls in deep excavations within water-rich sand layers. From an engineering perspective, these findings underscore the importance of prioritizing confined aquifer dewatering management, dynamically expanding settlement monitoring zones, and rigorously characterizing permeability profiles to mitigate excessive ground settlement and protect adjacent infrastructure. Full article

The Earth Pressure Balance (EPB) shield machine plays a pivotal role in underground tunnel excavation, where precise control of chamber pressure is essential for maintaining tunnel stability and minimizing risks. Traditional EPB control methods heavily rely on operator experience, resulting in delays and limited responsiveness to sudden geological changes. This paper presents an improved EPB mechanism model that builds upon traditional approaches, which primarily consider chamber pressure changes caused by soil volume variations. The improved model further incorporates the effects of excavation face pressure variations, arising from factors such as cutterhead soil extrusion and changing geological conditions. By integrating these additional influences, the model achieves more accurate predictions of chamber pressure. To further enhance performance, a hybrid modeling approach is proposed, combining the improved mechanism model with a data-driven component that compensates for residual prediction errors. The hybrid model is validated using field data from two distinct tunneling projects, demonstrating superior prediction accuracy and generalization capability compared to standalone mechanisms and data-driven models. The results confirm that the proposed hybrid model significantly improves pressure prediction accuracy and provides a more reliable solution for intelligent control of the EPB process. Full article

Soil colour and texture play important roles in identifying archaeological features during excavations, particularly in rescue archaeology where rapid and reliable interpretation is required. This study investigated the application of visible-near-infrared (VIS-NIR) soil spectroscopy for quantitatively characterising cultural heritage materials and archaeological soils on freshly exposed surfaces after topsoil removal during excavation. Surface soil spectra were collected using a portable spectrometer from nine features at a rescue excavation site in Hyeondo-myeon, Republic of Korea. A PCA-based spectral deviation approach was applied to detect deviations of archaeological soils from locally defined natural background spectra. Balanced accuracy values exceeded 0.70 under optimised configurations across all sites, with several sites achieving values above 0.80. Strong statistical discrimination coincided with spatially coherent clustering of elevated anomaly values corresponding to archaeologically identified feature zones. The 400–1000 nm wavelength range, combined with locally calibrated background spectra, yielded the most stable and reproducible performance. The proposed workflow demonstrates that field-based VIS-NIR spectroscopy can provide rapid, quantitative, and spatially interpretable support for archaeological feature identification. By integrating sensor-based spectral characterisation with anomaly mapping, the approach minimises interpretive subjectivity and improves analytical reproducibility in excavation decision-making processes. Full article

This study explains how an extremely low electrical earthing resistance was achieved in challenging gravelly soil conditions. In the existing soil, a resistance of 5 ohms was measured using traditional earthing techniques. After excavating and removing the granular soil, it was replaced with fine-grained, sandy-silty clay, then compacted after moistening, reducing earthing resistance to 2.5 ohms. The goal was to achieve a resistance below 0.5 ohms, which is necessary for the precise operation of robotic welding machines. To achieve this, a hybrid strategy was employed, combining deep earthing by drilling with ground-enhancing compounds in the gravelly soil. In İzmir-Torbalı, a 40 m-deep borehole was drilled to install a copper electrode in water-saturated clay below the groundwater level. To increase the conductivity of the granular soil and ensure contact with the electrode, the borehole was filled with graphite powder. As a result, the earthing resistance reached only 0.28 ohms, proving the effectiveness of this method in high-resistance soils. Full article

High-liquid-limit clay exhibits pronounced water sensitivity due to the strong electrostatic repulsion and weak interparticle bonding within its microstructure, which often limits its direct engineering uses and complicates the reuse of excavated clayey soils generated during the construction of transportation infrastructure. In this study, inorganic salts (KCl, CaCl₂ and FeCl₃) and carboxyl-containing polymers (PAAS, HPMA and CMC) were screened to construct organic–inorganic composite stabilization systems. Based on the screening results, an organic–inorganic composite system composed of CaCl₂ and sodium polyacrylate (PAAS) was developed to regulate interfacial interactions and induce microstructural reconstruction in clay. The synergistic mechanisms governing particle aggregation and dispersion were systematically investigated through Atterberg limit tests, zeta potential measurements, DLVO theoretical calculations, particle size analysis, scanning electron microscopy (SEM) and immersion disintegration experiments, combined with multivariate statistical modeling. Among the tested salt–polymer formulations, a composite system with 2% CaCl₂ and 0.1% PAAS showed the most favorable overall performance, achieving an optimal balance between electrostatic compression and steric stabilization, leading to enhanced structural integrity and delayed water-induced disintegration. Ca²⁺ ions compress the diffuse double layer and promote particle flocculation, whereas adsorbed PAAS chains introduce steric hindrance and interfacial modification. Their synergistic interaction reconstructs the pore–aggregate framework and regulates the interparticle potential energy landscape. DLVO analysis indicates that the optimized system attains a moderate critical interaction distance (h_c = 7.31 nm) and primary minimum depth (DPM = −2.72 × 10⁻¹⁶ J), reflecting a balanced interfacial bonding state. Multivariate statistical analyses further reveal a dual control pathway, in which consistency primarily governs disintegration duration, with additional contributions from surface electrochemical properties, while surface properties, soil structure and consistency collectively influence disintegration initiation. These findings elucidate the interfacial regulation and structural evolution mechanisms in organic–inorganic composite systems and provide insights into the design of composite modifiers for water-sensitive particulate materials, particularly for the resource reuse of high-liquid-limit clay excavated during the construction of transportation infrastructure and related geotechnical engineering applications. Full article

Ground-penetrating radar (GPR) has applications across many domains, including archaeology, mining, and infrastructure inspection. This review is specifically focused on urban subsurface utility mapping, where accurate detection of buried pipelines, cables, and conduits is critical for excavation safety and infrastructure management. Within this scope, two major barriers are identified: event–utility mismatch and the synthetic–field domain gap. Bibliometric analysis shows increasing reliance on deep learning, yet most methods remain limited to event-level hyperbola detection rather than utility-level inference. In real urban environments, radar responses are often affected by orientation-dependent signatures, clutter, overlapping reflections, and non-utility anomalies, making detected events difficult to map directly to physical infrastructure. In parallel, models trained on synthetic data frequently show limited field generalization because simulated radargrams do not fully reproduce soil heterogeneity, acquisition variability, and system artifacts. The review argues that future progress in urban utility mapping requires a shift toward utility-level reasoning supported by multi-sensor fusion, physics-guided learning, hybrid simulation–field datasets, and uncertainty-aware interpretation. Such advances are essential for making GPR outputs more reliable and actionable in urban engineering practice. Full article

Tunneling activity inevitably induces soil stress redistribution and ground deformation, which may affect adjacent existing pile foundations. Since many previous studies have mainly focused on circular tunnels, the effects of quasi-rectangular shield (QRS) tunneling on adjacent existing pile foundations are not well investigated and understood. In this study, a series of physical model tests were carried out to investigate the response of a single pile and pile group subjected to newly QRS tunneling beneath an existing circular tunnel in dry sand. Two distinct underpass cases were considered: an orthogonal underpass (QRS tunnel axis perpendicular to the circular tunnel axis) and an overlapping underpass (QRS tunnel axis aligned with the circular tunnel axis). The test results indicate that QRS tunneling-induced ground surface settlement and single-pile settlement in the overlapping underpass case were 3.6 and 1.2 times that in the orthogonal underpass case, respectively, with a narrower settlement trough. The axial force distribution along the single pile remained qualitatively consistent in both underpass cases, consistently exhibiting a downward load-transfer mechanism, and further leading to a monotonic growth pattern in axial force with progressive QRS tunnel excavation. The additional stress of the single pile was consistently higher in the overlapping underpass case, which had maximum axial force, negative bending moment, and maximum positive bending moment increases of 20%, 13%, and 6%, respectively, relative to the orthogonal underpass case. The front pile in the pile group exerted a pronounced shielding effect on the rear pile, while the restraining action of the pile cap also contributed measurably to the overall pile responses. Full article

The primary objective of this research is to quantitatively isolate the complex driving factors of slope deformation and explicitly reveal the long-term creep mechanism induced by early excavation unloading, thereby providing a theoretical basis for long-term stability evaluation. To achieve this, this study adopts a combined approach of multivariate statistical regression and numerical simulation inversion based on long-sequence monitoring data. First, a multivariate statistical regression model incorporating time-dependent, rainfall, temperature, valley width, and excavation components was constructed to quantitatively separate the contribution weights of each factor. Second, by introducing a rock–soil creep constitutive model, a refined finite element model was established to perform back-analysis of creep parameters and numerical simulation. The results indicate that two large-scale slope-cutting excavations were the direct triggers for the deformation, resulting in shear dislocation of the deep ancient sliding zone and superficial slippage. The dominant factors exhibit distinct phasic and spatial differences: before impoundment, the time-dependent component was absolutely dominant (>80%); after impoundment, low-elevation areas were significantly affected by valley width shrinkage (>60%), while high-elevation areas remained dominated by time-dependent deformation (>74%). Numerical simulation confirmed that the nature of the deformation is “excavation unloading-induced creep along the ancient sliding zone,” and the simulation results considering creep effects accurately reproduced the actual deformation characteristics observed in situ. It is concluded that the rheological effects induced by early excavation unloading are central to the control of long-term stability. Full article

Permeability anisotropy, which is widely present in natural soil deposits, plays an important role in controlling groundwater flow patterns and ground deformation during deep excavation dewatering. However, isotropic assumptions are still commonly adopted in engineering practice, making it difficult to accurately capture realistic subsurface hydraulic conditions. In this study, a deep foundation pit of a metro station in Jinan, China, is taken as a case study. A three-dimensional excavation–dewatering model incorporating permeability anisotropy is established using PLAXIS 3D to systematically investigate the influence of the permeability ratio (Kx/Kz) ranging from 0.1 to 10 on the seepage field evolution, dewatering influence radius, ground surface settlement, and consolidation time history. The results indicate that increasing permeability anisotropy promotes a fundamental transition of the seepage regime from vertically concentrated recharge to laterally dominated radial flow. Correspondingly, the dewatering influence radius exhibits a pronounced non-monotonic response to Kx/Kz, decreasing significantly with increasing permeability ratio and reaching a minimum at approximately Kx/Kz ≈ 5, followed by a slight rebound. Meanwhile, surface settlement profiles evolve from a localized concentration pattern to a widely distributed form as permeability anisotropy increases, accompanied by a remarkable outward expansion of the settlement influence zone. Both the magnitude and spatial distribution of settlement show high sensitivity to variations in permeability anisotropy. Based on these findings, a three-stage conceptual seepage structure model accounting for permeability anisotropy is proposed, characterized by vertically dominated flow, a transitional competition regime, and horizontally dominated flow. The staged evolution of seepage structures is shown to govern the non-monotonic variation in the dewatering influence radius and the spatial–temporal response of ground settlement. The results indicate a dual-scale influence mechanism of permeability anisotropy on dewatering-induced hydro-mechanical behavior, providing a theoretical basis for refined dewatering design and environmental impact assessment in deep excavation projects. Full article

In urban subway construction, shield tunneling inevitably passes in close proximity to existing pile foundations, inducing adverse effects on their internal forces and deformations. Taking the twin shield tunnels with small clearance adjacent to the bridge piles as the engineering background, this study establishes a three-dimensional finite element numerical model to investigate the deformation and internal force responses of the adjacent pile foundations under different pile lengths, twin-tunnel construction sequences, and tunnel face pressure conditions. The findings indicate that the primary influence zone affected by twin-tunnel excavation extends approximately twice the tunnel diameter (2D) before and after the pile foundation location. Compared with short piles, longer piles exhibit smaller vertical displacements. Meanwhile, the lateral displacements, additional axial forces and bending moments of medium and long piles increase, with their maximum values occurring near the tunnel centerline. For the near pile, when the right tunnel is excavated first, compared with the condition of the left-tunnel-first excavation, the lateral and vertical displacements slightly increase. In addition, the maximum additional axial force increases by 38.8%, while the maximum additional bending moment decreases by approximately 21%. Tunnel face pressure exerts a moderate influence on the vertical displacement of both the surrounding soil and pile foundation, while its effect on lateral displacement and internal forces is relatively insignificant. The tunnel face pressure within the range of 200 kPa to 300 kPa provides optimal control over pile foundation deformation. Full article

Accurately determining digging resistance during bucket–soil interaction is crucial for optimizing excavator working devices and power systems. To address measurement difficulties, a numerical simulation model based on the arbitrary Lagrangian–Eulerian (ALE) method was established and verified through excavation tests. Through orthogonal experiments, the influence of excavation parameters was studied, and the optimal compound digging trajectory was determined. The results show that increasing the excavation angle from 36° to 48° decreases the X-direction resistance and moment by 39.48% and 38.85%, respectively, though specific energy consumption (SE) increases. Additionally, optimizing arm movement speed reduces the X-direction resistance and moment. While ensuring the bucket load factor is suitable, reducing arm speed and a horizontal soil push during compound excavation effectively decreases SE. Finally, the optimal balance of digging resistance and SE can be achieved with a 300 mm bucket hydraulic cylinder displacement, a 1.5 s interval for initial arm and bucket movements, and an arm-to-bucket speed ratio of 5.5 for hydraulic cylinders. Full article

Assembled H-shaped steel strut (AHSS) has been widely applied in deep excavation projects. In this study, the collapse failure of AHSS C1 in a deep excavation project in China was investigated. The collapse of C1 was directly attributed to the settlement of its supporting columns in the mid-span, which was triggered by a nearby pit bottom leakage through an exploration borehole. Then the implementation of the emergency measures and reconstruction works were introduced. Theoretical and numerical pre-assessments confirmed that the reconstructed C1 exhibited adequate safety for strength, in-plane stability and out-of-plane stability, with all steel components and bolts within their safe limits. The good working performance of reconstructed C1 was finally verified through the monitoring results (i.e., strut axial force, soil horizontal displacement, column vertical displacement, road settlement and building settlement) of the foundation pit during the subsequent soil excavation and basement construction. This study is believed to provide references for future excavation projects using AHSS with similar risks. Full article