Grouting method is widely used in fields such as foundation reinforcement and building rectification. However, there is currently a lack of systematic research on the impact of grout diffusion on the stress field and grout reinforcement range within the unloaded soil under different grouting conditions. This paper conducts a series of grout diffusion experiments in sandy soil using a self-developed three-dimensional grouting system, and systematically analyzes the influence of water-cement ratio, grouting pressure, grouting volume and soil unloading degree on the stress increment in soil, the shape of grouting body, the grout diffusion radius and the grout reinforcement ratio. The results show that the most significant changes in soil internal stress caused by the slurry are located at the same burial depth plane as the grouting port, followed by the soil above the burial depth of the grouting port, and the soil below the burial depth of the grouting port has the smallest changes in soil internal stress. The average attenuation amplitude of the average stable stress increment in the soil after grouting is about 30% compared to the average peak stress increment in the soil. The average stress increment in the soil shows a trend of first increasing and then decreasing with the increase of water-cement ratio and grouting pressure, while the average stress increment in the soil increases with the increase of grouting volume and soil unloading ratio. The overall shape of the grouting body under different conditions is ellipsoidal, and the planar diffusion shape formed by the side wall grouting is approximately elliptical with a “large top and small bottom”. The equivalent diffusion radius of grout increases with the increase of grouting volume, soil unloading degree, and water-cement ratio, while it shows a pattern of first increasing and then decreasing with the increase of grouting pressure. For the average soil stress increment and the equivalent grout diffusion radius, the grouting volume exhibits the greatest influence within the tested parameter intervals, while the soil unloading degree shows the least effect.
Controlling the diameter of jet-grouted columns is difficult because of variable ground conditions and the complex interaction of grouting parameters. As jet grouting is increasingly used in space-constrained and traffic-intensive areas, traditional trial-and-error pilot tests are often impractical. This study proposes an integrated jet grouting process that couples real-time column diameter monitoring with immediate diameter uniformity control within conventional construction workflows. The proposed approach aims to improve grouting efficiency in interlayered soils and reduce geometric non-uniformity and the risk of seepage windows or weak sections occurring between columns. Field tests using a double-fluid jet grouting system were carried out to evaluate the proposed process. The results show that clay layers within the interlayered soil profile hinder column formation and cause irregular column shapes. Targeted water jet pre-cutting was applied to disintegrate clay structures, resulting in more uniform column diameters across different soil layers. By enabling a seamless transition from monitoring to corrective action based on real-time acoustic data, the proposed process allows immediate intervention when non-compliance with design requirements is detected. The proposed process improves quality and efficiency and provides practical guidance for jet grouting in interlayered ground conditions or transportation works with strict construction schedules.
Contaminated soil, post-stabilization/solidification, is frequently subjected to complex engineering environments. In Northwest China, the combined effects of chloride salt erosion and freeze–thaw cycles present significant challenges to foundation stability and construction projects by impairing the engineering performance of geopolymer-stabilized/solidified contaminated soil. To address this, a study was conducted involving coupled tests of chloride ion erosion and freeze–thaw cycles to systematically analyze the deterioration mechanisms of stabilized contaminated soil under these combined effects. Macroscopic performance was evaluated by monitoring the evolution of mass loss rate,unconfined compressive strength (with its loss rate), shear strength parameters (cohesion and friction angle), hydraulic conductivity,and toxic leaching concentration in the stabilized contaminated soil under varying salt solution concentrations and numbers of freeze–thaw cycles. Simultaneously, microscopic testing methods (XRD, SEM, NMR)and the modified BCR sequential extractionwere employed to investigate thechemical fraction transformation andunderlying mechanisms. The results show that chloride exposure produced a non-monotonic concentration-dependent response. Among the tested conditions, the 3% NaCl solution caused the most pronounced mechanical deterioration, whereas Pb2+ leaching generally increased under chloride exposure. The Pb2+ leaching concentration was first observed to exceed the regulatory limit of 5 mg/L after 8, 4, and 6 freeze–thaw cycles in 0%, 3%, and 5% NaCl solutions, respectively. Because measurements were conducted at two-cycle intervals, these values represent the experimentally observed stages of first exceedance rather than exact critical thresholds or field service-life limits. Microscopic observations indicate that freeze–thaw cycling and chloride exposure degraded cementitious products, exposed soil particles, and promoted crack development. The combined PCAS and NMR results suggest that newly formed fine pores and microcracks developed concurrently with the enlargement, interconnection, and coalescence of pre-existing pores, resulting in increased porosity, pore coarsening, and deterioration of macroscopic performance.
Producing flowable filling materials from waste soft clay provides a sustainable reuse pathway, yet their application is limited by inherently high compressibility associated with the high water content required for flowability. Hence, this study investigates the effectiveness of low-content sand addition in reducing compressibility of the stabilized clay-based material while maintaining workability. Two binders including cement and ground granulated blast-furnace slag (GGBS) were adopted, and the effects of binder content, water content, and sand volume ratio were examined. Before yielding, the recompression index (CR) is jointly controlled by strength and void ratio. However, the compression index (CC) corresponds to the stage where the cemented microstructure has yielded, after which compressibility predominantly depends on void ratio. Although increasing binder content from 60 kg/m3 to 80 kg/m3 markedly leads to a severalfold increase in strength, it does not reduce the compression index (CC), while a sand volume ratio of 0.15 decreases CC by 30.8–39.4% across different binder systems. Notably, specimens with and without sand exhibited similar coefficients of consolidation (cv) and hydraulic conductivity (k). Furthermore, this study proves the reduction of porosity is the governing mechanism for compressibility reduction within the investigated sand content range. Based on the mechanisms, this study proposes predictive relationships for the compressibility of stabilized clay–sand mixtures, offering a practical approach for compressibility control through minimal sand incorporation.
The 2024 Noto Peninsula Earthquake (Mw 7.6) and the subsequent tsunami caused extensive damage to coastal and riverine geostructures in the eastern Noto Peninsula, Japan. This paper presents field investigation results focusing on tsunami–ground interaction from a geotechnical engineering perspective. Severe damage was observed at Ukai Fishing Port, the Ukai River levee, Iida Port, and the Awazu coastal area. Field observations, borehole data, groundwater conditions, and portable dynamic cone penetration test results indicate that liquefaction of the foundation ground, and in some cases the embankment body itself, occurred at several sites. Seismic-induced settlement reduced crest elevations of levees and breakwaters, thereby facilitating tsunami overtopping and significantly amplifying inundation damage. At Iida Port, the eastern breakwater exhibited an atypical displacement mode that differed from previously reported tsunami-induced failure patterns. In the Awazu area, sinkholes near a coastal parapet were interpreted as resulting from piping triggered by transient hydraulic gradients during rapid drawdown following tsunami overtopping.Such combined external loading is not explicitly considered in the current design standards, and detailed design that simultaneously considers both a large earthquake (Level 2 earthquake) and a large-scale tsunami is technically challenging at present. The observed damage patterns suggest that when seismic loads exceed the levels assumed in conventional seismic design, it is important that the structure does not collapse instantaneously but retains ductility and toughness, so as to mitigate damage caused by subsequent external forces.
Carbonaceous rock is of easy disintegration, making it hard to prepare standard samples for assessing its compressive strength. The point load test was conducted on both fresh and weathered carbonaceous rocks to investigate the variation of compressive strength under different conditions. The shear strength of carbonaceous rock-mortar interface was measured and the corresponding stress–strain behaviors were systematically analyzed. The test results revealed that the point load test was one of the effective methods for evaluating compressive strength of carbonaceous rocks. The calculated compressive strength Rc presented obvious variability for fresh and weathered rocks, while their statistical distributions followed a normal pattern. The expected value of Rc can be selected as an evaluation indicator, and their values for fresh and weathered cases were respectively 127.65 MPa and 50.06 MPa. Two days of water soaking led to a reduction of Rc exceeding 50%, and the softening coefficient KR decreased to 0.38 with soaking time extended to one month. An exponentially decreasing trend between KR and soaking time was proposed to capture the experimental data. The weathered rock collected from the slope surface was classified into a highly weathered one due to its weathering coefficient of 0.392. The stress-displacement curves of rock-mortar interfaces can be roughly divided into: elastic, elastoplastic, softening, and stable parts. The great variability of cohesion and friction angle was consistent with the anisotropy and the disintegration of tested carbonaceous rock.
Large deformation hazards, such as crown collapse and sidewall squeezing, frequently occur during tunneling in deeply buried layered weak rock, where high in − situ stress and structural plane bring serious challenges to construction safety. This study focuses on the near − horizontal layered rock mass of the Yijun Tunnel on the Xi’an-Yan’an High speed Railway and investigates its deformation and failure mechanisms through geomechanical characterization, three − dimensional numerical simulation, and scaled physical model test to examine the combined effects of lateral pressure coefficient (λ), tunnel overburden depth (h), and stratum thickness (t) on the surrounding rock response. The results indicate that the lateral pressure coefficient plays a key role in the failure mode transition, while rock layer thickness and burial depth dominate different stress and deformation responses. Under the specific conditions considered in this study, the deformation mechanism evolves progressively as λ increases: when λ is relatively low (λ < 0.8), deformation is dominated by tensile response in the roof strata;in the intermediate range (0.8 ≤ λ ≤ 1.2), tensile-shear interactive behavior becomes evident; and when λ is relatively high (λ > 1.2), deformation is increasingly governed by bedding − controlled slip along weak interlayers. Under higher lateral stress conditions (λ ≥ 1.5), shear slip zones develop near the tunnel, accompanied by pronounced strain localization. Overall, within the scope of this study, the results provide preliminary insights into the instability mechanisms of stratified surrounding rock and highlight the importance of stress state and structural characteristics in controlling tunnel response. The findings may serve as a useful reference for deformation control in tunnels under similar geological conditions.
The exposure of plant roots caused by soil erosion significantly alters surface microtopography and runoff pathways; however, the specific mechanisms by which it affects hydrodynamic processes remain not fully understood. This study investigated how slope segment, exposed root distribution pattern, and runoff discharge influence the hydraulic characteristics of overland flow by simulated scouring experiments. Results revealed that transverse and cross-slope root arrangements effectively reduced flow velocity and erosive energy, whereas parallel arrangement had a minimal effect. Significant differences in Reynolds number, Froude number, and friction coefficient were observed among different exposed root distribution methods and slope segments, with transverse slope arrangement demonstrating better overall regulation of flow patterns compared to the other two distributions. Notably, stream power and unit stream power were significantly higher under the parallel arrangement, and shear stress was significantly higher on the upper and middle slope segments. Overall, exposed roots significantly reduced the erosion potential of overland flow compared to bare slopes. These findings help clarify the potential hydraulic mechanisms by which exposed root distribution patterns may influence overland flow.
The penetration of a jack-up leg equipped with a spudcan foundation is a critical operation for jack-up vessels (JUVs), which are widely employed in offshore wind farm installation and oil and gas drilling. The spudcan provides stable support on the seabed, thereby ensuring safe and reliable operations. Despite their importance, predicting the complex interactions between spudcans and seabeds, especially in low-permeability clay, remains a significant engineering challenge. In this study, an integrated experimental and numerical investigation of spudcan penetration and extraction processes is presented. Centrifuge model tests and in situ measurements were conducted to examine spudcan penetration dynamics and the resulting seabed deformation. Building on these findings, an axisymmetric Material Point Method (MPM) framework incorporating an explicit u-p formulation with a simple elasto-plastic constitutive model was developed. This model accurately simulates large deformations and soil–water–structure interactions, effectively reproducing key phenomena such as high pore pressure development in clay, general shear failure in sand, and the cavity and backflow behavior associated with deep penetration. Moreover, the model has been successfully validated against both laboratory and in situ field measurements, demonstrating its reliability for predicting the complex behavior of spudcan foundations under real-world conditions. The outcomes of this study can provide a solid basis for predicting spudcan foundation penetration and improving operational safety in offshore engineering applications.
Microbial clogging, as an environmentally friendly solution to leakage, utilizes microorganisms to form biofilm structures in soil, significantly reducing the pore size and permeability of the bio-soil. To enhance its efficiency, this study introduced a coupling-grafting modification to improve soil surface properties and microbial compatibility. The optimal modification conditions were determined, and microbial adhesion and anti-seepage performance were evaluated through bio-soil column tests. Surface property changes were further analyzed to clarify interaction mechanisms between the modified soil and microorganisms. The coupling modifier was prepared using a deionized water–ethanol system. Compared with unmodified soil, microbial attachment increased significantly, and the hydraulic conductivity of the modified bio-soil decreased by nearly one order of magnitude with a faster reduction rate. The modified soil exhibited greater roughness and hydrophobicity with a lower negative surface charge, promoting microbial clogging. Optimal conditions were 90 °C, 6% modifier concentration, and 3 h treatment. These results demonstrate that coupling-grafted modification effectively enhances microbial clogging efficiency, providing an eco-friendly seepage control strategy for sandy soils.
This study investigates the applicability of three-dimensional finite element analysis (3D FEA) for large-diameter monopiles under short-term loading conditions. Centrifuge model tests conducted on saturated, dense Toyoura sand were used to validate the 3D FEA, with a focus on load–displacement response, bending moment distribution, and excess pore water pressure. The results demonstrate that 3D FEA accurately captures the initial loading behavior and key resistance mechanisms, particularly for large-diameter monopiles. Furthermore, the Cyclic Contour Diagram (CCD) concept, a practical approach for predicting degradation due to cyclic loading, was examined. CCD-based degradation factors were compared with stiffness reductions observed in centrifuge model tests, showing reasonable agreement under nearly undrained conditions. Additional FEA incorporating degraded parameters derived from the CCD confirmed the potential of this approach, although limitations remain in accurately reproducing detailed monopile responses. This study highlights the effectiveness of the CCD concept, while emphasizing that its application in practical design requires careful consideration of factors such as load levels, drainage conditions, and the degree of soil mobilization along the monopile. The results provide additional insight into the applicability of CCD-derived degradation characteristics to large-diameter monopiles, highlighting the importance of drainage conditions and pile geometry when interpreting cyclic degradation at the pile level.
The ultimate bearing capacity of strip footing near rock slope (SFNRS) under oblique loads remains a theoretical challenge, as the existing analytical methods predominantly rely on a priori assumed kinematic mechanisms or numerical bound optimizations. To solve such a problem, this study proposes a rigorously modified stress characteristics method (SCM) incorporated with the generalized Hoek-Brown yield criterion. The core of proposed methodology lies in establishing a strictly statically admissible stress field that fundamentally accommodates complex oblique boundary conditions and variable footing setback distances. Based on the typical boundary value problems (BVPs) and the principle of minimum bearing capacity, the proposed framework autonomously captures the spontaneous transition among five distinct failure modes, completely eliminating the dependence on predefined failure patterns. The probable failure mode of SFNRS alters according to the different boundary conditions, which include the footing setback distance, load inclination, and slope geometry. Furthermore, a comprehensive parametric analysis reveals that the geological strength index (GSI) essentially improves the ultimate bearing capacity, while an increase in the load inclination angle significantly accelerates the transition of the critical slip surface from overall sliding failure to localized face failure, or even Prandtl’s foundation failure. Furthermore, quantitative thresholds for the critical setback distance and the critical slope height under oblique loads are established, providing novel theoretical insights and practical design guidelines for the safe placement of foundations adjacent to rock slopes.
This study investigates the longitudinal bending damage mechanisms of glass fiber-reinforced polymer trapezoidal core sandwich sheet piles (GFRP-TCSSP) used in levee reinforcement. By refining a discrete–continuum coupled numerical model, the soil–pile interaction forces at the ultimate plastic bending moment were extracted and efficiently replicated in the GFRP-TCSSP discrete element method (DEM) model using the granular membrane approach. This enabled realistic simulation of soil–pile interactions under lateral loading and revealed failure modes closely aligned with actual service conditions. The research systematically explores the effects of various constraint conditions on the evolution of bending damage in simplified GFRP-TCSSP models, with particular emphasis on the role of soil–pile interaction in optimizing structural performance. Results show that, under soil–pile constraints, initial cracks primarily form at the skin–core interface between the peak points of relative pressure coefficients on the upstream and downstream sides. This contrasts with traditional three-point and four-point bending tests, where cracks also develop near the central axis of the core layer. Notably, dynamic constraints effectively reduce the number of cracks. Furthermore, local reinforcement strategies targeting damage-prone regions significantly enhance bending strength, achieving performance comparable to global reinforcement while minimizing material costs.
A two-dimensional consolidation model for unsaturated–saturated soils under plane strain conditions is developed based on Fredlund’s and Terzaghi’s consolidation theories for unsaturated and saturated soils, respectively. Furthermore, an interfacial flow contact model is proposed based on the Hagen-Poiseuille law to describe the laminar flow induced by low-velocity pore water movement at the layer interface. Semi-analytical solutions for pore water pressure, pore air pressure, and settlement were derived using Laplace transforms, their inverses, and Fourier sine series expansion. The effects of the flow contact transfer coefficient (Rw) and flow partition coefficient (ηw) on pore water pressure, pore air pressure, and settlement are discussed based on these solutions. Results show that the interfacial flow contact resistance effect impedes the discharge of pore water, thereby generating a relative pore pressure gradient at the interface. Simultaneously, it slows the settlement rate of unsaturated–saturated soil systems. As the flow contact transfer coefficient increases or the flow partition coefficient decreases, the relative pore pressure gradient at the interface becomes more pronounced, resulting in a slower settlement rate.
The formation of an artificial freezing curtain is severely constrained by groundwater seepage. Traditional numerical methods have limitations in addressing the interaction between seepage flow and freezing soil along a moving freezing front. To address this, an enthalpy-based lattice Boltzmann model is proposed to study the development of an artificial freezing curtain subjected to seepage flow. The numerical model is verified through three benchmarks: analytical solutions for phase change and convective heat transfer, and experimental test results, and is then applied to two representative configurations: a single freezing pipe and a row of three pipes subjected to groundwater flow. In both cases, seepage flow restrains the formation and development of freezing soil. For a single pipe, the development of the freeze radius is restrained the most upstream, followed by midstream and downstream. For a row of three pipes, the closure position moves towards downstream compared with when there is no seepage flow. This shift arises from the asymmetric cooling pattern induced by groundwater seepage: upstream inflow continuously supplies heat that delays freezing front advancement, whereas downstream thermal interference is weaker, allowing faster front propagation. Compared with the initial ground temperature and pipe spacing, pipe diameter has less effect on the closure position. The closure time is approximately linearly related to the water-facing length, and the slope increases with seepage velocity.
This study explores the characteristics of permeation grouting and induced ground deformation in various fully saturated sands using a two-dimensional scaled physical model with bentonite-cement grout. A bentonite-cement grout was injected into Hele-Shaw-type soil models under varying soil types, injection rates, water-cement ratios, and vertical effective stresses, while soil displacement was monitored using particle image velocimetry. Results show that groutability was strongly influenced by the particle size of host soils. In coarse sands, grouting remained stable, and deformation was mitigated by increasing the water-cement ratio and effective stress. In fine and silty sands, conversely, higher injection rates triggered unstable grouting with fracture generation, leading to irregular ground heaving, and the fracture-induced deformation was also significant even at a higher water-cement ratio and effective stress. Particle-level dimensionless analysis considering the shear-thinning characteristics of the bentonite-cement grout reveals that the grout seepage pressure can serve as an indicator of the grouting pattern: stable versus unstable grouting. This study proposes new groutability criteria incorporating both the grain size ratio between grout and host soil and viscous pressure normalized by effective confining stress. These findings are expected to improve grouting design strategies through experimental observations and particle-scale mechanics.
Sulfate-rich soils (SRS) exhibit poor engineering properties, and studies focusing on the stabilization of these soils remain limited in the existing literature. Previous research has shown that the use of calcium-based stabilization agents, such as cement and lime, during the treatment of SRS can lead to adverse effects such as efflorescence, swelling, and associated deformation issues. Therefore, selecting an appropriate stabilization technique is critical to ensuring the safety and long-term performance of engineering structures built on such soils. In recent years, geopolymer-based soil stabilization has garnered increasing attention as a sustainable alternative to traditional cement-based methods due to its lower carbon footprint. In this study, an environmentally friendly and innovative geopolymer stabilization approach was applied for soils with extremely high sulfate content (284,400 ppm), taking into account potential issues such as swelling and settlement associated with calcium-based additives. The proposed method aims to improve the resistance of sulfate-rich soils (SRS) to deformation by increasing their bearing capacity and compressive strength. Ground granulated blast furnace slag (GGBS), metakaolin (MK), Class F fly ash (FA), sodium hydroxide (NaOH), and sodium silicate (Na2SiO3) were used in the production of geopolymers. During sample preparation, the deep soil mixing (DSM) method was considered, and unconfined compressive strength (UCS) tests were conducted to evaluate the strength performance of sulfate-rich soils (SRS) stabilized with geopolymer. Additionally, samples cured for 28 days were subjected to durability tests. The experimental results showed that when GGBS, MK, and FA were used separately, GGBS and FA contributed more effectively to early-age strength development, while MK had a greater effect on long-term strength increase. Considering the strength values obtained after 7 and 28 days of curing, the maximum strength increase of 64.13% was achieved in the MK100 specimen. While the combined use of GGBS and MK resulted in an average 38% increase in specimen strength, the combined addition of GGBS and FA caused an average 22% decrease in strength. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses were performed to investigate the microstructural changes, chemical composition, and elemental distributions of the stabilized SRS. Additionally, Fourier-transform infrared spectroscopy (FT-IR) analysis was performed to identify the chemical properties and functional groups present in the samples, and the findings were comprehensively evaluated. (c) 2026 Japanese Geotechnical Society. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
This paper introduces an expandable plate anchor (ExPLA). It is a novel anchoring system for floating wind turbines. The ExPLA is a plate anchor consisting of two plates connected by a hinge. It is installed on the seafloor in a folded state to minimize penetration resistance. When the hinge is pulled up, the folded plates expand horizontally and exhibit a high anchoring capacity. To evaluate the feasibility of this concept, 1 g tests were conducted using 1/100 scale models. The folded anchor model was embedded at three depths in its folded state and then pulled upward to verify whether it expands. The expansion process was observed directly using a visualization technique based on transparent quartz and refractive index matching. The test results demonstrate that anchors with specific geometries can expand as these are pulled out. The key observations identified the geometrical parameters: a back slope angle of at least 20° ensures successful expansion, whereas a dip angle over 20° reduces the pullout distance required for deployment. The theoretical considerations based on the moment equilibrium around the hinge are consistent with the experimental results and reveal the relationships among the earth pressure coefficients, frictional angles, and anchor geometry. Finally, the potential and limitations of the ExPLA as an anchoring system for floating wind turbines are presented.
Microbially induced calcite precipitation (MICP) is an eco-friendly soil reinforcement technique. However, its application is limited by bacterial loss, insufficient CaCO3 precipitation, and weak interfacial bonding. This study introduced calcium carbonate-based marble particles as functional additives to modify the granular medium of MICP-treated sand. Unconfined compressive strength (UCS) tests were performed to evaluate the reinforcement performance, and the associated mechanisms were analyzed through bacterial retention, CaCO3 precipitation, interfacial cementation, and microstructural characterization. The results showed that, within the tested range, increasing marble content improved the mechanical performance of MICP-treated sand. Among the investigated groups, the specimen containing 30% marble showed the highest peak UCS, reaching 2103.7 kPa, nearly twice that of the control group. This enhancement was associated with three main effects: (1) the rough and calcite-rich marble surfaces improved bacterial retention, with the immobilization rate reaching 95.6% in the 30% marble group; (2) CaCO3 yield increased by more than 110%, and the post-sonication mass loss rate decreased to below 7.0%, indicating denser and more stable cementation; and (3) marble incorporation was associated with an increase in calcite content and a corresponding decrease in vaterite content, together with increases in hardness and elastic modulus of the cemented regions by 216.7% and 170.0%, respectively. These results indicate that marble particles can enhance MICP-treated sand through improved bacterial retention, more favorable CaCO3 nucleation and cementation conditions, and participation in skeleton stabilization, thereby improving the mechanical performance of the treated soil. This study highlights the potential of carbonate-based solid waste as a functional medium-modifying material in MICP and provides a useful basis for sustainable soil reinforcement in geotechnical engineering.
