Steel corrosion-induced expansive stresses in reinforced concrete progressively generate rustcracked systems that degrade serviceability and mechanical performance, motivating reliable repair strategies. This study uses rust-cracked reinforced mortar specimens to investigate EPD repair and its hybrid strengthening with externally bonded CFRP, linking deposition metrics to mechanical recovery. EPD parameters (repair time, curing time, voltage, and crack width) and CFRP configurations (layer number, fabric specification, and layout) were varied, and flexural and compressive strengths were measured. EPD process descriptors-surface film thickness, a curing progress index, and penetration metrics-were related to flexural and compressive strength recovery. Flexural enhancement increases nearly linearly with surface film thickness and the curing progress index. Compressive recovery is governed by bonded interphase continuity and uniformity and shows a negative association with mean penetration depth. An operational EPD window of 20-40 V with 24 h repair and 24 h curing produces nearly continuous films with limited mouth-skinning and Joule-heating porosity, restoring about 14 % flexural and 19 % compressive strength. Wider cracks (0.6-1.2 mm) provide a lower resistance path for the EPD resin colloid, yielding higher enhancement ratios but slightly lower repaired strengths than narrow cracks (0.3 mm). Hybrid EPD-CFRP strengthening raises beam flexural strength to about three times the unrepaired level and increases compressive strength of wrapped prisms by 70-100 %, with larger gains for higher fabric specification and wrap continuity. Failure mapping clarifies transitions from bonded flexure to interface-governed shear tension and wrap-synergy modes in bending, and from rust-guided splitting to confinement-controlled crushing in compression, providing mechanistic guidance for field deployment.

This study proposes an analytical model to investigate the kinematic response of end-bearing piles in nonhomogeneous unsaturated soils subjected to vertically propagating seismic P-waves. The soil profile exhibits continuous heterogeneity characterized by power-law variations in Lamé constants, density, porosity, and bulk modulus of three-phase along the pile shaft, while the pile is modeled as a standard beam with fixed-base boundary conditions. Governing equations for the coupled soil-pile system are derived employing the three-phase poroelastic theory within a continuum mechanics framework. The mathematical formulation utilizes Laplace transforms combined with operator decomposition techniques to decouple wave propagation equations, with potential functions employed to address compressional wave interactions. Frequency-domain solutions are obtained through rigorous enforcement of displacement-stress continuity conditions at the pile-soil interface and predefined boundary constraints under P-wave excitation. Validation through degenerate case comparisons demonstrates consistency with classical solutions for homogeneous saturated and single phase soils profiles. Parametric analyses systematically explore how gradient variation patterns, soil saturation, air-entry value, pile slenderness ratios, and pile-soil modulus ratios on seismic response characteristics.

This study develops an analytical framework to assess the torsional response of floating piles by considering the fractional viscoelasticity and transverse isotropy of unsaturated soils, addressing the critical yet overlooked influence of the finite-thic kness soil layer between the pile tip and bedrock. By introducing a fictitious unsaturated soil pile (FUSP) methodology, the pile is virtually extended to bedrock, with the FUSP inheriting the fractional-order viscoelastic properties of the surrounding soil. The governing equations integrate three-phase interactions, transverse isotropy, and fractional calculus-based viscoelasticity, enabling unified modeling of both floating and end-bearing piles. The derivation process involves the techniques of separation of variables and eigenfunction expansion, leading to closed-form solutions for the frequency-domain torsional impedance, while semi-analytical time-domain responses under semi-sine pulse excitation are obtained via inverse Fourier transformation and convolution theory. Parametric analyses demonstrate the sensitivity of pile head impedance and twist angle to FUSP and pile length, saturation, transverse isotropy ratios, fractional derivative order, and viscoelastic relaxation times.

ObjectiveTo reduce tram construction disturbance on existing road traffic and to shorten construction periods, some regions have begun to adopt prefabricated pile-slab subgrade structures. However, current research on such structures remains limited, and the dynamics characteristics of piles, slabs, and key connection nodes of the prefabricated pile-slab structures have not yet been clarified. Therefore, it is necessary to analyze the dynamics characteristics of the load-bearing slabs and piles in both tram cast-in-place and prefabricated pile-slab structures. MethodUsing Jiaxing Tram (phase I) project as the research background, multiple sensors are installed on-site to obtain data on subgrade soil pressure beneath slabs and soil stratification settlement for both cast-in-place and prefabricated pile-slab structures. Finite element numerical models of the above two subgrade types are established to investigate and clarify the dynamics characteristics of their load-bearing slabs, piles, and connection nodes under tram dynamic loading. Result & Conclusion Compared with the cast-in-place pile-slab structure, the prefabricated pile-slab subgrade exhibits larger values in certain dynamics response parameters of its load-bearing slabs, piles, and connection nodes. Regarding the dynamics characteristics of the load-bearing slabs, the peak vibration acceleration at the mid-span section of both structural types is greater than that at the pile-top section, while the peak tensile and compressive stresses at the mid-span section differ significantly. In terms of pile dynamics characteristics, the peak acceleration of piles in both structural types decrease with the increasing depth. As for the connection node dynamics characteristics, the stresses experienced by the bolts connecting the load-bearing slabs and piles in the prefabricated pile-slab subgrade corresponds to the tramway load and exhibits periodic variation.

Reinforced concrete structures are prone to rust expansion cracking during service. Electrophoretic deposition repair is one of the effective coping technologies, but in actual engineering, the width and location of rust expansion cracks are not fixed, which affects the repair efficiency. This study was conducted by controlling the crack width and location variables. The results show that an increase in crack width reduces the inter-electrode resistance, expands the effective action area of the electric field, enhances the electrophoretic deposition rate of the repaired molecules, and increases the improvement amplitude of the waterproof performance of the specimens. For every 0.1 mm increase in width, the molecular deposition rate increases by 7 %. By comparing the repair of cracks in different locations, the lower crack achieved a filling rate of 92 % due to the synergy of electric field force and gravity, and the density of the epoxy resin film was the best. The lateral crack cause the deposition path to shift downward due to gravity, presenting an asymmetric filling (filling rate of 73 %). The upper crack needs to overcome the gravity barrier, and the filling rate in the middle drops to 57 %. The research provides a theoretical basis for the optimization of specific crack repair parameters.

The shield tunnel, as a critical infrastructure component of rail transit systems, is prone to segment misalignment, a common defect that can lead to segment deformation, cracking, and water leakage, thus compromising the tunnel’s safety. High-density point cloud data are acquired using structured light binocular vision. Through intelligent recognition of point cloud circumferential seam features, this method automatically locates discontinuities and analyzes the direction of the circumferential seam main axis. The segment misalignment values are then automatically quantified using the zonal average elevation calculation method, with quadratic surface fitting applied to batch compute the misalignment data. To address challenges such as limited camera field of view and the impact of overlap on registration accuracy, FPFH, RANSAC, and multi-stage ICP algorithms are employed for point cloud registration and stitching. Experiments conducted on the Nansha-Zhuhai Intercity Railway shield tunnel demonstrate that this method can achieve a detection precision of ± 0.2mm. Compared to 3D laser scanning methods, it offers advantages in terms of lightweight design and lower cost, thus providing valuable technical support for the intelligent operation and maintenance of rail transit tunnels.

Urban construction adjacent to piled embankments often induces complex lateral soil movements, giving rise to horizontal soil arching (HSA). This mechanism governs stress redistribution and soil–pile interaction but remains less understood than vertical arching. This study investigates the evolution and influencing factors of HSA through combined laboratory experimental model and finite element simulations. Physical tests were performed with varying pile spacings under lateral loading, complemented by strain, stress, and displacement measurements. The results reveal that HSA initiates with soil compaction in front of piles, followed by triangular stress distributions and parabolic stress trajectories. Smaller pile spacing stabilizes arches and promotes spanning across piles, whereas larger spacing leads to arch weakening and collapse. The validated FEM model further enabled parametric analyses. Cohesion was found essential for arch initiation, with a threshold effect beyond which additional cohesion had limited impact. Friction angle showed little influence once arches were established. By contrast, elastic modulus and Poisson’s ratio strongly affected arch persistence: higher stiffness reduced stress differentials, weakened soil–pile interaction, and lowered arching efficiency. These findings clarify the formation mechanism of HSA and provide insights for optimizing pile spacing and soil conditions to improve stability in urban geotechnical engineering.

This study presents an advanced fictitious unsaturated soil pipe pile (FUSPP) methodology for analyzing torsional dynamics of hollow pipe piles in fractional viscoelastic unsaturated cross-anisotropic soils. The FUSPP framework extends classical fictitious pile theory by establishing dual viscoelastic domains that preserve soil's Riemann-Liouville fractional properties and cross-anisotropy, while incorporating interfacial continuity at pipe-soil boundaries. Governing equations integrate three-phase unsaturated poroelasticity with independent anisotropy tensors for external/internal soils and fractional constitutive relations. Frequency-dependent impedance solutions are derived through cylindrical eigenfunction expansion, explicitly resolving coupled boundary conditions for torsional wave propagation. The FUSPP configuration mechanically equivalates pile tip sediments via viscoelastic length parameters. Parametric studies reveal critical dependencies on pipe geometry, anisotropy contrast, saturation effects, fractional order, and viscoelastic relaxation time ratios, demonstrating characteristic dual-peak impedance spectra induced by hollow pipe-fractional viscoelastic coupling. This methodology provides a computational paradigm for offshore pile design in complex strata.

This study investigates the kinematic response of large-diameter end-bearing pile in viscoelastic saturated transversely isotropic soils under seismic P-waves. By integrating a fractional-order viscoelastic constitutive model into the dynamic governing equations of saturated transversely isotropic soils based on de Boer's porous media theory, a coupled displacement-pore pressure formulation is developed to characterize wave propagation. The soil reaction along the pile shaft is analytically derived using variable separation, while the pile's longitudinal vibration is modeled as a Rayleigh-Love rod to account for lateral inertia effects. Wavefield decoupling is employed to isolate scattered waves from the total wavefields, enabling precise analysis of soil-pile interaction dynamics. After validating the proposed model, parametric studies systematically explore the effects of transverse isotropy, fractional derivative order, stress relaxation time, strain relaxation time and pile Poisson's ratio on key response metrics, including kinematic amplification, interaction factors, pile displacement, frictional force, and free-field soil displacement. The proposed model advances the theoretical basis for analyzing wave-driven soil-pile systems in complex geological settings.

Long-term axial performance of pile foundations in soft marine clays is governed by consolidation-driven effective-stress evolution, which controls the mobilization of negative skin friction (NSF) and dragload transfer along the pile. This study presents an integrated one-dimensional nonlinear consolidation-load transfer framework for a single end-bearing pile. The soil module incorporates (i) non-Darcian flow, (ii) the Yin-Graham elastic visco-plastic (EVP) model with a creep-strain limit to represent time-dependent deformation, and (iii) time-dependent continuous drainage boundaries (CDB) to model gradual dissipation at partially drained interfaces. The pile response is evaluated using a consolidation-informed shaft load-transfer relation and a hyperbolic base resistance model. The governing equations are solved with a Crank-Nicolson time-marching scheme and inner Picard iterations to ensure numerical stability and convergence. The framework predicts the time histories and depth profiles of excess pore-water pressure, soil deformation, skin friction, and pile axial force. Model reliability is demonstrated by mesh and time-step sensitivity checks and by three validation cases: the 1D EVP consolidation benchmark, consolidation-induced skin-friction development, and an instrumented centrifuge test on an end-bearing pile in consolidating clay, where the proposed model yields consistently improved agreement. Parametric and sensitivity analyses further quantify the relative roles of EVP creep, nonDarcian flow, and CDB in governing the consolidation timescale and the long-term axial performance of pile foundations.

This study offers a comprehensive and advanced understanding of the torsional response of piles partially embedded in fractional-order viscoelastic unsaturated transversely isotropic soils, accurately capturing the true viscoelastic properties and particle orientation of the soil as formed during deposition. Based on Biot's threephase porous media wave equations and considering the coupling effects between the immiscible fluids (water and air) in the pores, the dynamic governing equations for fractional-order viscoelastic unsaturated transversely isotropic soil are established. The soil vibration displacement is solved using the method of separation of variables. In the frequency domain, employing the transfer matrix method and considering the continuity and boundary conditions of the pile-soil system for both the embedded and exposed portions, the analytical solution for the torsional complex impedance at the pile head of a partially embedded single pile in fractionalorder viscoelastic unsaturated transversely isotropic soil is derived. Furthermore, a semi-analytical solution for the pile head response in the time domain under half-sine pulse excitation is obtained through inverse Fourier transform and convolution theorem. Numerical examples are presented to investigate the effects of the parameters of the fractional-order viscoelastic constitutive model and the pile-soil parameters on the torsional complex impedance at the pile head.

ABSTRACTA novel theoretical model is proposed to investigate the torsional response of a pile in fractional‐order viscoelastic unsaturated transversely isotropic soil with imperfect contact. This model employs Biot's framework for three‐phase porous media along with the theory of fractional derivatives. Unlike previous models that assume continuous displacement at the pile–soil interface, this study uses the Kelvin model to simulate relative slippage between pile–soil contact surfaces (imperfect contact). Incorporating fractional‐order viscoelastic and transversely isotropic models to describe the stress‐strain relationship, comprehensive dynamic governing equations are derived. Using the separation of variables method, inverse Fourier transform, and convolution theory, analytical solutions for the frequency domain response and semi‐analytical solutions for the time domain response of the pile head under semi‐sine pulse excitation are obtained. Using numerical examples, the effects of model parameters in the fractional‐order viscoelastic constitutive model, pile–soil relative slip and continuity model, and soil anisotropy on the torsional complex impedance, twist angle, and torque are presented.

This paper investigates the dynamic response of an exponentially graded unsaturated porous transversely isotropic half-space under time-harmonic loading. Transversely isotropic elasticity coefficients and material density are assumed as functions of depth in exponential forms with considerations of compressibility, viscous and inertial coupling of soil particle, pore water and pore air. By means of Hankel integral transform and Vieta theorem, the elastodynamic governing equations are derived in a cylindrical coordinate system, and the general solutions of displacement and stress components are presented in a transformed domain. The accuracy of the proposed model is validated by conducting a comparison with two established benchmark studies in the literature. Utilizing the Gauss-Kronrod algorithm, numerical evaluations are conducted to investigate the influence of frequency, heterogeneity parameter, transversely isotropic parameters, and the degree of saturation on the dynamic response of exponentially graded unsaturated transversely isotropic half-space.

The soil-squeezing effect induced during the construction of secant piles can significantly affect the surrounding strata and existing structures. Managing the deformation caused by secant pile construction is crucial to mitigate adverse effects. While much has been studied on the effects of secant pile construction on surrounding soil, few studies focus specifically on the deformation of high-speed railway bridge foundations in these contexts. This study integrates on-site measurements with numerical analysis. It investigates the deformation effects of secant pile construction on surrounding strata and adjacent highspeed railway bridge foundations. A finite element model was developed. The model was used to validate the feasibility of the calculation method for cylindrical cavity expansion and the equivalent simplification of three secant piles in simulating the soil squeezing effect during construction. Based on these findings, an additional finite element model was created to assess the deformation of high-speed railway bridge piles resulting from the construction of secant piles. The model's computations considered scenarios involving secant piles constructed on single-side and on double-sides (both symmetrically and asymmetrically) of the bridge pier. This article provides insights into the impact of secant pile construction on adjacent bridge piles and offers recommendations for mitigating deformation.

Horizontal soil arching is a critical stress redistribution mechanism developing between pile rows under lateral loads from adjacent excavations or embankments. This phenomenon significantly affects the performance of pile-based protection systems, yet its spatial formation and depth-dependent geometry remain insufficiently understood. In this study, a comprehensive methodology is developed for determining the spatial shape of horizontal soil arching through an integrated experimental–numerical approach. Laboratory model tests on single-row piles under controlled lateral loading were complemented by validated three-dimensional (3D) finite-element simulations. The investigation revealed that soil arching efficiency is primarily controlled by pile spacing-to-diameter ratio and pile diameter as geometric parameters, along with soil cohesion and internal friction angle as strength parameters. A methodology was developed to determine arch geometry by analysing horizontal stress distributions, identifying the leading edge through stress peaks and the trailing edge through maximum stress gradients. This approach enabled systematic characterisation of the 3D arch morphology. Numerical analyses established that horizontal soil arches exhibit parabolic geometry, with the leading edge maintaining constant geometry with depth while the trailing edge shows progressive expansion. Mathematical equations were developed to predict arch geometry based on pile and soil parameters, providing a scientific basis for optimising pile row design in urban excavation projects.

We aimed to study the influences of creeping properties of different backfill materials on the earth pressure above the high-filled cut-and-cover tunnel(HFCCT)that adopted the relatively low-com-pacted loess(RLC)as the load reduction method.The FLAC3D(fast lagrangian analysis of continua)was used to establish numerical models of HFCCT to analyze the RLC reduction effects when the creep properties of the backfill materials were significant(loess)and insignificant(dry sandy gravel)respec-tively.At the same time,the influences of the related parameters variations(the width of RLC,the height of RLC and the location of RLC)on the vertical earth pressure above the HFCCT were further investiga-ted.The results show that the load reduction effect of RLC is different under different backfill materials.The RLC load reduction can exert a better load reduction effect in fillers with insignificant creep proper-ties.When backfill works are completed,the load reduction effect of RLC is activated by generating the relative vertical displacement difference between the backfill materials above the HFCCT and the both sides of HFCCT.After construction,if the backfill material is loess with significant creeping property,the displacement of the RLC and backfill material increases over time,the vertical earth pressure above HFC-CT also increases over time,which indicates the load reduction effect of RLC gradually decreases.If the creep property of backfill material is insignificant,the displacement of RLC still increases over time,but the vertical earth pressure above HFCCT decreases over time,which suggests the load reduction effect in-creases.In addition,the long-term effect of changes in the geometric parameters of the RLC on the earth pressure above the HFCCT is closely related to the creeping properties of the backfill materials,which has an optimal value.The above results have certain reference value for the long-term load reduction of HFCCT.

Considering the soil skeleton to be statically transversely isotropic, the viscous and inertial coupling among three phases, along with the capillary pressure, the torsional dynamic response of an end-bearing pile in homogeneous unsaturated transversely isotropic soil under time-harmonic torsional load is investigated. The separation of variables method is employed to derive the torsional dynamic governing equations of unsaturated transversely isotropic soil in a cylindrical coordinate system, and pile is modeled as a 1D elastic theory. By combining the boundary conditions of the pile and soil, as well as the continuity conditions at the pile-soil interface, further employing the inverse Fourier transform and convolution theorem, fundamental analytical solutions for the torsional behavior of the pile are derived in both the frequency domain and time domain. Comparisons between the proposed solution and the two existing solutions indicate that the presented model exhibits stronger applicability, as it can simultaneously transition to both saturated transversely isotropic soil and unsaturated isotropic soil. Eventually, a parametric study is conducted to examine the influence of soil anisotropy, degree of saturation, pile-soil shear modulus ratio and pile length on the torsional dynamic response of end-bearing pile.

An analytical solution for investigating the torsional dynamic response of a pipe pile in unsaturated poroelastic transversely isotropic soil under time-harmonic load is proposed. By employing the Biot's type three-phase porous media model and the three-dimensional continuum theory, taking into account the transversely isotropic characteristics of the soil skeleton, as well as the viscosity and inertial coupling between different phases, distinct dynamic governing equations are derived for the soils surrounding and inside the pipe pile. By considering the boundary and continuity conditions at the interface between the pipe pile and the soils surrounding and inside the pipe pile in the frequency domain, a mathematical expression is derived to describe the torsional dynamic behavior of the pipe pile. A parametric study aimed to investigate how the anisotropy of the soils surrounding and inside the pipe pile (soil plug) impacts its torsional complex impedance, twist angle, and torque was conducted. The parametric study also considered variations in saturation, pile lengths, porosity, the height of the soil plug and excitation frequencies to explore the effects of these parameters on the torsional behavior of the pipe pile.

The effectiveness of load-reduction techniques often diminishes due to creep behavior observed in geomaterials, as loess backfill is used, the load reduction rate of high-filled cut-and-cover tunnels (HFCCTs) after creep will decrease by 10.83%, posing a threat to the long-term stability of deeply buried structures such as HFCCTs. Therefore, a geotechnical solution is crucial to ensuring sustained effectiveness in load-reduction strategies over time. This study utilizes a finite-difference method to examine three promising measures for mitigating creep effects. Our analysis focuses on the time-dependent changes in earth pressure atop the cut-and-cover tunnel (CCT) and the internal distribution of cross-sectional forces, including bending moment, shear force, axial force, and displacement. Results indicate that the creep behavior of load-reduction materials significantly influences the internal force distribution. Furthermore, sustained load reduction is achieved when utilizing low-creep materials like dry sandy gravel as backfill soil, which needs to be borrowed from other sites. Additionally, integrating concrete wedges with load-reduction techniques facilitates a more uniform stress distribution atop CCTs.