Search Results (154)

Water leakage in underground construction works is a prominent and persistent quality defect, particularly for the joint between the foundation slab and prestressed anti-floating anchors or piles. Previous studies have focused on optimizing the structural details to improve impermeability, while overlooking water seepage caused by insufficient adhesion at the interface between the polyethylene (PE) sheath and concrete. Therefore, this study aimed to enhance this interfacial adhesion through the hydrophilic modification of PE, thereby improving the impermeability of anti-floating anchors or piles prestressed with retarded-bond tendons. Physical blending modification was adopted in which hydrophilic PE granules were incorporated into ordinary PE. The variations in the water contact angle and mechanical properties of PE were analyzed at contents ranging from 0% to 8%. Adhesion strength tests were conducted to evaluate the changes in the interfacial adhesion strength between ordinary PE, modified PE, and concrete with different cement grades. Water impermeability tests were performed to measure the impermeability grades of concrete specimens reinforced with unbonded, ordinary retarded-bond, and modified retarded-bond prestressing tendons. The results showed that with increasing hydrophilic PE granule content, the hydrophilicity of PE improved markedly, while its mechanical properties improved slightly. A content of 8% hydrophilic PE granules is recommended. Debonding occurs between ordinary PE and concrete, whereas the adhesion strength of hydrophilic PE to concrete gradually increases with the cement grade. The impermeability grade of concrete with modified retarded-bond prestressing tendons is six grades higher than that with ordinary retarded-bond prestressing tendons, reaching P8. This indicates that the incorporation of hydrophilic PE granules significantly improves the impermeability of anti-floating anchors or piles prestressed with retarded-bond tendons. Full article

With the construction of transportation networks in mountainous areas under the Western Development Strategy, double-row pile foundations on slopes have been widely applied. However, due to the distortion of the soil stress field, their load distribution mechanism under bidirectional loading is extremely complex. To investigate the internal force distribution laws and deformation and failure modes, a systematic study was conducted utilizing theoretical derivation: 60 scale indoor physical model tests, and 3D refined finite element numerical simulations. The results show that the force distribution of double-row piles in slope environments differs significantly: the upper-row piles, affected by active earth pressure and sliding thrust, bear significantly higher load than the lower-row piles; meanwhile, the lower-row piles, constrained by stronger deep soil, can more fully utilize their vertical bearing capacity. Parametric analysis indicates that the terrain slope has a nonlinear amplification effect on the displacement difference at the pile top, with 50° being the critical mutation slope that triggers the failure of connection joints. In addition, the deformation mode of double-row piles undergoes a change when the pile spacing exceeds 5 times the pile diameter. Therefore, in practical engineering design, the traditional concept of symmetrical reinforcement should be abandoned in favor of differentiated bending reinforcement targeting the shallow surface layer of the upper-row piles and the deep inflection point of the lower-row piles. For working conditions with a slope greater than 50°, additional measures such as prestressed anchor cables must be applied to reduce the sliding load. Meanwhile, the row spacing should be strictly controlled within 5 times the pile diameter to fully ensure the diaphragm effect and the overall synergistic stability of the structure. Full article

Although the long-term behavior of ground anchors depends fundamentally on interfacial behavior, the independent effect of the strand–grout interface on load loss has not been comprehensively investigated. This study establishes a physical model testing method that isolates the strand–grout interface and systematically investigates both short-term and long-term load loss behavior. Pull-out tests and long-term monitoring tests were conducted using grout uniaxial compressive strength ($q_u$ = 18–30 MPa) and bond length ($L_b$ = 900–1500 mm) as primary design variables. Long-term monitoring confirmed that prestress loss at the strand–grout interface is induced by the progressive pull-out displacement of the strand over time, following a logarithmic decay pattern. The load reduction coefficient n was significantly more sensitive to $L_b$ than to $q_u$; n increased sharply from 0.015 to 0.069 as $L_b$ decreased. Anchors with insufficient bond length exhibited secondary load reduction behavior that disrupted the stable log-linear decay, posing significant risk to long-term performance. Based on RMSE analysis of the fitted logarithmic model, a minimum monitoring period of approximately 50 days is recommended for reliable long-term prediction when bond length is adequate. These findings identify $q_u$ and $L_b$ as the governing parameters, providing a quantitative basis for optimizing prestress design and enhancing the long-term reliability of anchor systems. Full article

Typhoons and extreme rainfall significantly exacerbate engineering risks during deep excavation construction. Based on an asymmetric deep excavation project in Hainan under the influence of Super Typhoon Yagi, this study analyzes the evolution of Soil Mixing Wall (SMW) pile deformation and prestressed anchor cable axial forces through field monitoring. PLAXIS 3D 2023.2.0.1059 finite element software is employed to investigate the deformation response of the supporting structure under the coupled effects of excavation and extreme rainfall, revealing the optimal design for embedment depth under such adverse conditions. The results indicate that the presence of existing buildings leads to asymmetric deformation and pronounced corner effects. The synergistic action between the capping beam and the waler transforms the pile displacement profile from a cantilever mode to a bow-shaped distribution. Parametric analysis determines the optimal embedment depth to be 10.6 m and the critical safety embedment depth to be 7.6 m. Under a 400 mm/d typhoon rainfall condition, the maximum horizontal displacement of the supporting structure increases by 1.6–2.0 mm compared to non-rainfall conditions. With a 3.5 m water head, increasing the embedment depth from 6.1 m to 10.6 m reduces the maximum horizontal displacements on the east, south, and west sides by 98%, 42%, and 10%, respectively. This study provides a theoretical basis and practical reference for embedment depth optimization in typhoon-prone regions. Full article

As an active reinforcement technology, prestressed anchor cables are susceptible to environmental corrosion during long-term service. Corrosion occurs and progresses more rapidly, especially in an alternating wet–dry environment, which can degrade the mechanical properties of prestressed anchor cables and may ultimately lead to failure. Current methods typically evaluate the mechanical properties of anchor cables based on cross-sectional loss calculated from the average weight loss ratio. However, this uniform-corrosion assumption may underestimate the effect of corrosion on mechanical performance. In this study, a testing apparatus for corroding prestressed anchor cables under alternating wet–dry conditions was developed. The apparatus enabled accurate loading and nondestructive sampling. Using this apparatus, alternating wet–dry corrosion tests and mechanical tensile tests were conducted on anchor cables under different stress levels. The relationship between weight loss ratio and mechanical properties was then analyzed. Based on this relationship, an equation was derived to calculate the breaking strength of corroded anchor cables in alternating wet–dry environments. The service life estimated using this equation was closer to that observed in actual anchor cable failure cases. This indicates that the proposed equation provides more accurate predictions than methods based on the uniform-corrosion assumption. Full article

The sustainable utilization of multiple reclaimed pavement materials is a critical pathway toward green highway construction. This study investigates the performance and synergistic mechanisms of cold-recycled mixtures incorporating both Reclaimed Asphalt Pavement (RAP) and Reclaimed Cement-Stabilized Base (RCSB), using emulsified asphalt as the primary binder. A comprehensive experimental program was conducted to evaluate the effects of reclaimed material proportions, mixing sequences, and curing ages on the mechanical strength, moisture susceptibility, and high-temperature stability of the mixtures. Microscopic characterization via Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) were employed to elucidate the Interfacial Transition Zone (ITZ) evolution. Results indicate that an optimal RCSB incorporation range of 20–40% establishes a robust “stone-to-stone” rigid skeleton, significantly enhancing the splitting strength (up to 0.87 MPa) and durability (Splitting Strength Ratio, TSR > 91%). SEM observations confirm the formation of a dense interpenetrating network structure within this range, where cement hydration products and asphalt films achieve optimal chemo-physical bonding. Exceeding 40% RCSB leads to a moisture-starved state and a sharp decline in dynamic stability due to insufficient binder coating. Micro-morphological characterization reveals that the transition from macro-interfacial debonding to a robust cohesive failure mode is the fundamental driver for the performance peak at 20–40% RCSB. SEM observations confirm the formation of a dense interpenetrating network structure, where cement hydration products successfully anchor into the asphalt film. This optimized ITZ effectively eliminates the stress concentration and aggregate crushing seen in high-RAP mixtures, thereby ensuring superior mechanical integrity. Furthermore, a pre-wetting mixing sequence ensures a high-energy mineral surface that promotes the heterogeneous nucleation of cement. SEM results show that this prevents the competitive adsorption between cement and asphalt, transforming the ITZ from a friable, loose state into a densified crystalline adhesive matrix. Full article

Local anchor failure can trigger progressive collapse of excavations, during which capping beams and walers, as key load-transferring components, experience significantly increased internal forces. However, the evolution of their mechanical responses remains unclear. In this study, large-scale physical model tests were conducted to systematically investigate the effects of anchor parameters (prestress, failure rate, and installation height), external hazard scenarios (local over-excavation and surface surcharge), and capping beam connection strength on the mechanical responses of capping beams and walers. The results show that applying prestress increases the lateral stiffness of the retaining structure and reduces the bending moment increase in the capping beam. Intermittent instant failure is the most unfavorable condition for the capping beam, inducing larger bending moments than rapid instant failure or slow failure. When anchors are installed at the waler level, the bending moment in the waler is significantly larger than that in the capping beam when anchors are installed at the capping beam level. Local over-excavation subjects the capping beam to larger shear forces at the edges of the over-excavation zone, making it susceptible to shear failure; accordingly, shear strengthening should be implemented at these locations, and strict control over the extent of over-excavation is required. Under surface surcharge, the critical load-bearing component varies with anchor installation height: when anchors are installed at the capping beam level, the retaining piles should be strengthened, whereas when anchors are installed at the waler level, the waler should be strengthened. The wall–anchor support system exhibits superior integrity compared to the pile–anchor system. Capping beam connections effectively disperse failure loads and reduce the increase in axial forces of adjacent anchors. Furthermore, I-steel connections for inter-panel strengthening can further enhance structural stability and increase the number of anchor failures required to trigger progressive collapse. These findings provide a scientific basis for the progressive collapse-resistant design of anchor-supported excavations. Full article

The prestressed anchor cable is widely used in foundation pit engineering, but its universal bending shape in the anchorage section will significantly affect the load transfer and stress distribution. Based on Cox’s shear-lag model, this paper presents a theoretical analysis of the load transfer behavior at the anchor cable–grout interface and establishes an elastic distribution model of axial force and shear stress that accounts for the anchor cable shape. Furthermore, the influence of cable shape on the elastic stress distribution in the anchorage section under different load conditions, different anchorage lengths, and different bending radii is compared and analyzed. Finally, through a comparative analysis between the model calculation results and experimental data, the proposed distribution model shows good agreement with the experimental results. The findings reveal the evolution of the elastic stress distribution in the anchorage section under different cable shapes and provide a theoretical reference for the axial force loss of prestressed anchor cables in service. Full article

The combined arch theory provides an effective means for designing support parameters in roadways within loose and fractured surrounding rock. A clear understanding of the internal stress evolution during the load-bearing process of the combined arch is of guiding significance for optimizing roadway support. Taking the 11308 return airway of a mine in Inner Mongolia as the engineering background, this study adopts a combined research approach of theoretical calculation, numerical simulation and laboratory testing. It systematically investigates the internal stress evolution of the anchored combined arch load-bearing structure in roadways with loose and fractured surrounding rock. The load-bearing capacity and failure characteristics of the anchored combined arch under different roof support schemes are explored and analyzed. An optimized support scheme for the loose and fractured roof is proposed and applied in the field, and the monitoring results verify its effectiveness. The results indicate that bolt density is a key factor affecting the load-bearing performance of the combined arch. As bolt spacing decreases, the vertical stress concentration in the anchored structure increases, and its deformation resistance is enhanced. During the stage from load-bearing to failure of the combined arch, the changes in vertical and horizontal stresses within the arch become more stable, and the load-bearing capacity is significantly improved. Comparison between the model test results and theoretical calculations shows good agreement, verifying the rationality of the theoretical calculations. Pressure sensors were pre-installed in the laboratory model to monitor the vertical stress changes in the anchored structure throughout the loading process, and numerical simulations confirmed the stress concentration effect of the combined arch. It was also found that the instability of the anchored structure is controlled by the shear plane at the arch feet. Finally, the bolt spacing in the 11308 return airway of the Inner Mongolia mine was optimized to 0.7 m, and field monitoring was introduced. The maximum roof surface settlement displacement was 15 mm, and the maximum roof separation was 3 mm, confirming that these parameters can meet the roadway stability requirements. Full article

Utilizing excavated waste soil to level gullies offers significant advantages in terms of engineering economy and construction efficiency. However, the stability and deformation risks of high-fill embankments in mountainous gullies under rainfall conditions have attracted significant attention, particularly when such structures are located adjacent to residential areas. This study compares two design schemes for highway high-fill embankments, Scheme 1: high-fill slope supported by stabilizing piles and prestressed anchors, and Scheme 2: ordinary waste soil as the core, foamed lightweight soil (EPS) as the edge band, and reinforcement by a micro-pile retaining wall system. Finite element analysis was used to evaluate the Factor of Safety (FOS), displacements of retaining structures, and characteristic slope points under three conditions (no rainfall, heavy rainfall, and heavy rainfall with soil strength deterioration). The results show that Scheme 2 reduces total costs by 3.5%, shortens the construction period by 14%, and cuts maintenance costs by 65%, with a minimum FOS of 1.56 under extreme rainfall. Further parametric analysis of Scheme 2 optimized key design parameters, and field monitoring data over 6 months verified the reliability of the numerical simulation. This study provides a transferable design-verification pathway for combining lightweight and conventional fills in high embankments, offering technical support for similar projects in complex mountainous areas. Full article

Active support systems are being increasingly applied in the control of large deformation in soft rock tunnels, and exploring the bearing characteristics of prestressed anchor bolts is of great engineering value for improving the long-term stability of tunnel structures. To address the problems of insufficient quantitative characterization of the bearing performance of prestressed anchor bolt support in soft rock tunnels and the difficulty of small-scale model tests in revealing the synergistic bearing law of support and surrounding rock, this study took a 350 km/h double-line high-speed railway tunnel as the prototype and established a large-scale tunnel structure model test system to conduct comparative tests under three working conditions: unsupported, ordinary bolt support, and prestressed anchor bolt support. By monitoring the tunnel failure process and mechanical response of the support structure throughout the test, the failure modes, bearing capacity, deformation characteristics, and axial force distribution of anchor bolts of tunnels under different support forms were systematically analyzed to quantitatively reveal the active support mechanism and bearing strengthening effect of prestressed anchor bolts. The results show that the design bearing capacity of the tunnel model with prestressed anchor bolt support is increased by 127.3% and 31.6% compared with that of the unsupported and ordinary bolt support models, and the ultimate bearing capacity is increased by 120.0% and 43.5%, respectively. Its secant stiffness in the initial loading stage reaches 80.0 kPa/mm, which is five times that of the ordinary bolt support and can effectively restrain the early plastic deformation of the surrounding rock. When the design bearing capacity is reached, the tensile stress of prestressed anchor bolts accounts for 40.2~69.8% of the ultimate tensile strength, with a more uniform axial force distribution and a much higher utilization rate of material mechanical properties than ordinary anchor bolts, which can fully mobilize the bearing potential of deep rock mass and realize the synergistic bearing of support and surrounding rock. This study accurately quantifies the bearing strengthening law of prestressed anchor bolts on tunnel support systems and clarifies the core mechanism of their active support. The research results provide important experimental basis and theoretical reference for the optimal design and engineering application of prestressed anchor bolts in soft rock tunnel engineering. Full article

The long-term prestress relaxation of soil anchors embedded in saturated clay is a critical issue affecting the safety of geotechnical structures such as slopes and foundation pits. Traditional integer-order constitutive models are often unable to accurately describe the nonlinear and time-dependent relaxation behavior observed in such anchorage systems. Based on fractional calculus theory, this study establishes a constitutive model for the coupled stress relaxation behavior of soil anchors and saturated clay. The Riemann–Liouville fractional derivative and the two-parameter Mittag-Leffler function are introduced to represent the material memory effect and continuous relaxation characteristics. To achieve reliable parameter identification, a hybrid optimization strategy combining the Adaptive Hybrid Differential Evolution (AHDE) algorithm and the Levenberg–Marquardt (L-M) method is proposed. The proposed model and identification approach are validated using field monitoring data from soil anchors in a slope engineering project at the Guangxi Friendship Pass Port. The results show that the proposed model can accurately reproduce the entire stress relaxation process, with a coefficient of determination of R² = 0.9517. Parameter sensitivity analysis further clarifies the influence of key parameters, including the fractional order and viscosity coefficient. The proposed approach provides a systematic theoretical framework and practical reference for the analysis and prediction of long-term prestress relaxation in soil anchorage systems. Full article

Two types of basalt fiber-reinforced polymer (BFRP) anchor cables—a Tension-concentrated anchor cable (TCAC) and a Pressure-dispersed anchor cable (PDAC)—were developed through structural modification of the rod body and implemented for reinforcing fractured rock masses on highway tunnel slopes in western Henan Province, China. The feasibility of replacing conventional steel rods with BFRP bars and the corresponding anchorage mechanisms were investigated. The experimental results indicate that the axial force distribution differs markedly between the two anchors. The TCAC exhibits a decreasing axial force with depth, forming a concave distribution under low load and a convex distribution under high load, with the force approaching zero beyond 100 cm. In contrast, the PDAC displays a relatively uniform axial force that sharply decreases near the bearing plate, and, under increasing load, the axial force at the anchorage end tends to rise; Both anchors demonstrate single-peak interfacial shear stress distributions. For the TCAC, the peak progressively shifts toward deeper regions with increasing load, whereas the peak of the PDAC consistently appears near the bearing plate, with only its magnitude increasing. Stability analysis using GEO5 software reveals that the slope safety factor increases from 1.32 (without anchors) to 1.36 (with anchors), thus satisfying the design requirements. The results reveal the different anchoring mechanisms of tension-concentrated anchor cables and pressure-dispersed anchor cables, providing practical guidance for their selection and application in slope stabilization engineering. Full article

Prestressed concrete (PSC) beams are widely used in bridges and large structures due to their high load-bearing capacity and crack resistance. However, owing to their complex construction process, they are highly sensitive to temperature variations. Implementing temperature monitoring at this stage helps assess the actual mechanical behavior and effective prestress of the beam, providing a reliable basis for construction control and prestress adjustment. This study aims to investigate the mechanical performance of a bidirectionally stiffened composite tensioning and anchoring system developed earlier by the research team during the construction phase and to elucidate the effect of temperature on the mechanical behavior of pretensioned prestressed concrete beams. By deploying a monitoring system integrated with high-precision sensors, synchronized temperature and displacement data during tensioning, pouring, and curing stages were obtained. Field-measured data were used to validate finite element models under different thermal load conditions. The results indicate that the heat of hydration of concrete causes a temperature difference of 12.0 °C at the end form, leading to a maximum displacement of 0.2 mm at the top of the anchor plate. Notably, a temperature change of 22 °C induces a prestress fluctuation of 0.12% to 0.3%. The numerical model demonstrates strong accuracy, with the highest agreement with experimental data and an error of less than 7.5%. These findings provide a scientific basis for compensating prestress losses and controlling the deformation of prestressed concrete beam structures, playing a critical role in ensuring the long-term safety and performance of structures under complex working conditions. Full article

Epileptogenesis is commonly defined by the emergence of spontaneous seizures after an initial insult; however, convergent experimental and clinical evidence indicates that the underlying disease process begins well before seizures become clinically detectable. During this pre-seizure phase, persistent molecular cascades remodel synaptic plasticity, circuit architecture, and glial–immune signaling. These processes are associated with trait-like alterations in cognition, affect, and behavior. Despite their clinical relevance, these neurobehavioral signatures remain poorly integrated into molecular models of epileptogenesis and are rarely considered as translational biomarkers of disease progression. This review synthesizes evidence linking core epileptogenic molecular cascades—maladaptive synaptic plasticity, glial–immune signaling, oxidative–metabolic stress, and activity-dependent gene regulation—to reproducible alterations in executive control, cognitive flexibility, emotional regulation, and motivational–social behavior. We outline an integrative framework in which these phenotypes are conceptualized as system-level readouts of progressive network reconfiguration rather than nonspecific “comorbidities” or mere consequences of recurrent seizures. Within this perspective, neurobehavioral markers can complement electrophysiological and molecular measures by capturing disease-relevant changes during windows when anti-epileptogenic interventions would be most effective. To increase mechanistic specificity, we provide representative pathway and gene-level anchors across epileptogenesis stages, a structured molecular-to-neurobehavioral mapping, and an operational biomarker panel specifying confounders and minimal controls. These anchors are included to ground the framework in experimentally documented molecular nodes with stage-dependent relevance; examples are representative rather than exhaustive, and evidence strength is indicated as preclinical mechanistic versus associative human observations. Finally, we discuss methodological requirements for biomarker validity (specificity, temporal anchoring, and cross-model consistency) and outline how integrating molecular and neurobehavioral trajectories may refine target discovery and improve the translation of anti-epileptogenic strategies. Conceptualizing epileptogenesis as a progressive disease process with measurable pre-seizure neurobehavioral signatures may broaden biomarker strategies beyond seizure occurrence and support the development of disease-modifying interventions. Full article