Search Results (1,487)

To accelerate the dissipation of excess pore water pressure, enhance the bearing capacity of piles, and mitigate long-term settlement in soft ground, a novel green and lowcarbon pile foundation technology, termed the precast drainage pile (PDP) technology, is proposed. This innovative approach integrated precast pipe piles with prefabricated vertical drains (PVDs) attached to their sides. The piles were installed using static pile pressing and were subsequently subjected to vacuum-induced negative pressure to facilitate soil consolidation, which enhances the resource utilization rate of pile foundations and promotes the sustainable utilization of soft soil foundations. To investigate the bearing characteristics of the PDP, this study combined the shear displacement method for piles with the consolidation theory of soft soil foundations. A calculation model for the load-settlement behavior of precast piles, accounting for the influence of vacuum-induced soil consolidation, was derived, establishing a method for analyzing the load transfer mechanism of PDPs. The reliability of the theoretical model was validated through comparisons with engineering test results. Building on this foundation, the influence of factors such as consolidation period and pile length on the bearing characteristics of PDPs was analyzed. The results demonstrated that, compared to a 10 m precast pile without drainage, the ultimate bearing capacity of single piles with drainage durations of 3, 7, 14, and 28 days increased by 7.3%, 12.7%, 20.3%, and 29.6%, respectively. Furthermore, under a 7-day drainage condition, the bearing capacity of piles with lengths of 10 m, 20 m, and 30 m increased by 12.7%, 12.8%, and 13.1%, respectively. Overall, the findings of this study provide a theoretical basis for the research, development, and design calculations of this new sustainable pile technology. Full article

It is difficult to meet environmental requirements via the coarse treatment methods of landfilling and open-air storage of construction waste. At the same time, the consumption of building materials in highway engineering is enormous. Using construction waste as a filling material for proposed roads has become a research hotspot in recent years. This paper starts with basic performance tests of recycled construction waste materials, and then moves on to laboratory experiments conducted to obtain the road performance of the recycled materials, the testing of key indicators of post-construction filling quality of the roadbed, and analyses of the deformation pattern of roadbed filled with construction waste. Additionally, the ABAQUS finite element software was used to establish a numerical model for roadbed deformation and analyze the roadbed deformation under different compaction levels and vehicle load conditions. The experimental results show that the recycled material has a moisture content of 8.5%, water absorption of 11.73%, and an apparent density of 2.61 g/cm³, while the liquid limit of fine aggregates is 20% and the plasticity index is 5.4. Although the physical properties are slightly inferior to natural aggregates, its bearing ratio (25–55%) and low expansion characteristics meet the requirements for high-grade highway roadbed filling materials. The roadbed layer with a loose compaction of 250 mm, after eight passes of rolling, showed a settlement difference of less than 5 mm, with the loose compaction coefficient stabilizing between 1.15 and 1.20. Finite element simulations indicated that the total settlement of the roadbed stabilizes at 20–30 mm, and increasing the compaction level to 96% can reduce the settlement by 2–4%. Vehicle overload causes a positive correlation between the vertical displacement and shear stress in the base layer, suggesting the need to strengthen vehicle load control. The findings provide theoretical and technical support for the large-scale application of recycled construction waste materials in roadbed engineering. Full article

The Himalayan belt, formed due to the Cenozoic convergence between the Eurasian and Indian craton, acts as a storehouse of large amounts of strain, resulting in large earthquakes from the Western to the Eastern Himalayas. Glaciers also occur over a major portion of the high-altitude Himalayan region. The impact of earthquakes can be easily studied in the plains and plateaus with the help of well-distributed seismogram networks and these regions’ accessibility is helpful for field- and lab-based studies. However, earthquakes triggered close to high-altitude Himalayan glaciers are tough to investigate for the impact over glaciers and glacial deposits. In this study, we attempt to understand the impact of earthquakes on and around Himalayan glaciers in terms of vertical displacement and coherence change using space-borne synthetic aperture radar (SAR). Eight earthquake events of various magnitudes and hypocenter depths occurring in the vicinity of Himalayan glacial bodies were studied using C-band Sentinel1-A/B SAR data. Differential interferometric SAR (DInSAR) analysis is applied to capture deformation of the glacial surface potentially related to earthquake occurrence. Glacial displacement varies from −38.9 mm to −5.4 mm for the 2020 Tibet earthquake (M_w 5.7) and the 2021 Nepal earthquake (M_w 4.1). However, small glacial and ground patches processed separately for vertical displacements reveal that the glacial mass shows much greater seismic displacement than the ground surface. This indicates the possibility of the presence of potential site-specific seismicity amplification properties within glacial bodies. A reduction in co-seismic coherence around the glaciers is observed in some cases, indicative of possible changes in the glacial moraine deposits and/or vegetation cover. The effect of two different seismic events (the 2020 and 2021 Nepal earthquakes) with different hypocenter depths but with the same magnitude at almost equal distances from the glaciers is assessed; a shallow earthquake is observed to result in a larger impact on glacial bodies in terms of vertical displacement. Earthquakes may induce glacial hazards such as glacial surging, ice avalanches, and the failure of moraine-/ice-dammed glacial lakes. This research may be able to play a possible role in identifying areas at risk and provide valuable insights for the planning and implementation of measures for disaster risk reduction. Full article

Isolation piles are critical for mitigating excavation-induced tunnel displacements, yet two unresolved challenges persist in tunnel engineering: (1) controversies regarding the influence of key parameters (e.g., pile head depth, pile length, and pile-to-pit distance) on their performance, and (2) insufficient understanding of the effects on both horizontal and vertical displacement control of tunnel. These challenges stem from the current research focus on isolated displacement components or simplified scenarios, which fails to address the complex interactions between key parameters and the deformation mechanisms. To address these gaps, this study proposes a hybrid validation framework integrating a three-dimensional finite element model (HS-Small constitutive model) with field monitoring data. A concept of “control efficiency” is introduced to quantify the effectiveness of isolation piles, complemented by a parametric sensitivity analysis framework. By synergizing the mirror image method and statistical theory, the research reveals a dual-path control mechanism involving displacement blocking and tunnel geometric reconfiguration. The findings advance the state of the art by resolving controversies over critical parameters and establishing a unified theoretical framework for coupled displacement control, providing actionable insights for optimizing isolation pile design in engineering practice. Full article

The conventional polymer gel has high initial viscosity and short gelation time, making it difficult to meet the requirements of deep profile control in offshore reservoirs with large well spacing and strong heterogeneity. This paper evaluates the performance and core plugging capacity of novel functional polymer gels and microspheres to determine the applicability of core permeability ranges. On the heterogeneous core designed based on the reservoir characteristics of Block B oilfield, optimization was conducted separately for the formulation, dosage, and slug combinations of the polymer gel/microsphere. Finally, oil displacement experiments using polymer and microsphere combinations were conducted on vertically and planar heterogeneous cores to simulate reservoir development effects. The experimental results show the novel functional polymer gel exhibits slow gelation with high gel strength, with viscosity rapidly increasing four days after aging, ultimately reaching a gel strength of 74,500 mPa·s. The novel functional polymer gel and polymer microsphere can effectively plug cores with permeabilities below 6000 mD and 2000 mD, respectively. For heterogeneous cores with an average permeability of 1000 mD, the optimal polymer microsphere has a concentration of 4000 mg/L and a slug size of 0.3 PV; for heterogeneous cores with an average permeability of 4000 mD, the optimal functional polymer gel has a concentration of 7500 mg/L and a slug size of 0.1 PV. In simulations of vertically and planarly heterogeneous reservoirs, the application of polymer agent increases the oil recovery factor by 53% and 38.7% compared to water flooding. This realizes the gradual and full utilization of layers with high, medium, and low permeability. Full article

To address the issue of vertical settlement in existing tunnels beneath newly constructed two-lane tunnels, and to mitigate further impacts on tunnel operations, it is essential to investigate the effect of tunnel construction on the integrity of the existing tunnel structure. A calculation formula for the vertical displacement of the existing tunnel is derived by simplifying the calculation model and employing a two-stage analysis method. A three-dimensional numerical model of the double-line shield tunnel beneath the existing tunnel of Dalian Metro Line 4 is established using Midas GTS NX finite element software 2021(v1. 1). The study focuses on the influence of the new tunnel’s excavation on the existing tunnel, examining how various parameters in the shield construction process affect the settlement. Through comparative analysis of theoretical calculations, numerical simulations, and engineering monitoring data, the results indicate that the calculated displacement settlement trends align closely with the numerical simulation and are consistent with the field monitoring data. The findings provide valuable insights for the development of effective protection measures for existing tunnels during shield tunnel construction. Full article

Background/Objectives: Correct supervision during the performance of resistance exercises is imperative to the correct execution of these exercises. This study presents a proposal for the use of Morisita–Horn similarity indices in modelling with machine learning methods to identify changes in positional sequence patterns during the biceps-curl weight-lifting exercise with a barbell. The models used are based on the fuzzy logic (FL) and support vector machine (SVM) methods. Methods: Ten male volunteers (age: 26 ± 4.9 years, height: 177 ± 8.0 cm, body weight: 86 ± 16 kg) performed a standing barbell bicep curl with additional weights. A smartphone was used to record their movements in the sagittal plane, providing information about joint positions and changes in the sequential position of the bar during each lifting attempt. Maximum absolute deviations of movement amplitudes were calculated for each execution. Results: A variance analysis revealed significant deviations (p < 0.002) in vertical displacement between the standard execution and execution with a load of 50% of the subject’s body weight. Experts with over thirty years of experience in resistance-exercise evaluation evaluated the exercises, and their results showed an agreement of over 70% with the results of the ANOVA. The similarity indices, absolute deviations, and expert evaluations were used for modelling in both the FL system and the SVM. The root mean square error and R-squared results for the FL system (R² = 0.92, r = 0.96) were superior to those of the SVM (R² = 0.81, r = 0.79). Conclusions: The use of FL in modelling emerges as a promising approach with which to support the assessment of movement patterns. Its applications range from automated detection of errors in exercise execution to enhancing motor performance in athletes. Full article

As a result of the 2017 Pohang earthquake, numerous piloti-type structures incurred damage, and the cause was attributed to the wide spacing of transverse reinforcement. Improper spacing of transverse reinforcement can lead to brittle failure of columns, potentially causing the collapse of buildings. This study aimed to analyze the failure mode of columns where load and displacement are concentrated due to vertical irregularity, and to quantify the spacing of shear reinforcement according to the degree of vertical irregularity to prevent shear failure of the column. First, a vertically irregular frame with vertical irregularity and an RC moment frame with the same upper and lower structural systems was modeled, and the failure mode of the column was analyzed. In this paper, the failure modes were classified into shear failure, flexure–shear failure, and flexural failure based on the shear capacity ratio. The analysis results showed that in the case of vertical irregularity, the shear demand of the column was evaluated as high due to the high flexural stiffness of the horizontal members, and the failure mode of the column was classified as shear failure. The impact of the spacing of shear reinforcement on the shear strength of the structure was also examined. Next, an analysis was performed according to the degree of vertical irregularity by adjusting the thickness of the first-floor shear wall, and as a result, the proportion of the entire columns classified as shear failure increased as the vertical irregularity increased. It was confirmed that the minimum spacing of shear reinforcement of 150 mm specified in Korean standards becomes inadequate when the degree of vertical irregularity exceeds 2.6. At a vertical irregularity of 8.3, the spacing required to prevent shear failure decreased to 136 mm, which is 9.33% less than the minimum specified by the Korean standards. This indicates that even if the code’s minimum spacing is adhered to, shear failure can still occur in columns. In order to prevent shear failure of the column, the spacing of the shear reinforcement should be designed smaller, because the shear force increases as the vertical irregularity increases. For piloti-type structures with high horizontal irregularity, there is a need to design shear reinforcement narrower than the minimum standard to prevent shear failure of the column. Full article

High-rise pile cap structures, such as sea-crossing bridges, suffer from long-term degradation due to continuous corrosion and scour, which seriously endangers structural safety. However, there is a lack of research on this topic. This study focused on the long-term performance and dynamic response of bridge pile foundations, considering scour and corrosion effects. A refined modeling method for bridge pile foundations, considering scour-induced damage and corrosion-induced degradation, was developed by adjusting nonlinear soil springs and material properties. Furthermore, hydrodynamic characteristics and long-term performance, including hydrodynamic phenomena, wave force, energy, displacement, stress, and acceleration responses, were investigated through fluid–structure coupling analysis and pile–soil interactions. The results show that the horizontal wave forces acting on the high-rise pile cap are greater than the vertical wave forces, with the most severe wave-induced damage occurring in the wave splash zone. Steel and concrete degradation in the wave splash zone typically occurs sooner than in the atmospheric zone. The total energy of the structure at each moment under load is equal to the sum of internal energy and kinetic energy. Increased corrosion time and scour depth result in increased displacement and stress at the pile cap connection. The long-term dynamic response is mainly influenced by the second-order frequency (62 Hz). Full article

In situ vertical load field tests were carried out on two bored piles used in the Chizhou Highway Bridge across the Yangtze River, both of which were rooted piles. Based on the test results, such as those on the relationship between the load and settlement, axial force distribution, and the relationship between shaft friction and pile–soil relative displacement, the vertical load transfer mechanics of the rooted piles were analyzed. The results showed that the load-carrying curves of the rooted piles vary gradually and also that the rooted piles exhibit the bearing characteristics of friction piles because the loads at the pile tips are less than 15% of the total bearing capacity of the piles. The slope of the axial force distribution curve of the rooted piles first increased at the upper interface and then decreased at the lower interface of the root-reinforced zone. The axial force of the rooted piles decreased faster in soil layers where the piles had roots, which can be explained by the fact that roots share the vertical load with piles and that roots improve the bearing properties of piles. Considering the shaft and end resistance of the roots on the piles, the relationship between load and settlement of the rooted piles was calculated by a three-line model based on the load transfer method. The results calculated from the model were in good agreement with the results from the tests. The results from the tests could inform the design and analysis of rooted piles. Full article

Karst geology creates a complex environment with diverse landforms, blurred boundaries, and multi-factor interactions. This paper presents a new drilling pile installation method: drill to a set depth, clean the hole, insert prefabricated piles, and drive or vibrate them to the target elevation. It suits tough geological conditions well. Pile foundations bear both axial and lateral eccentric loads. To explore prestressed high-strength concrete (PHC) pile foundations under eccentric vertical loads in karst areas, on-site bearing capacity tests were conducted. The results show that as load eccentricity increases, PHC pile foundation-bearing capacity drops notably. A finite element model was developed to analyze the stress and strain behavior of PHC pile foundations under eccentric loading in complex geological conditions, aiming to assess their bearing capacity and stability. Key findings include: (1) Under constant external load, the maximum displacement of the PHC pile foundation increases with greater load eccentricity. (2) Enhanced concrete strength reduces the maximum displacement of the pile foundation, while the peak stress remains stable. (3) The height of karst caves has a minimal impact on the bearing capacity and deformation of PHC pile foundations. These results highlight the importance of considering load eccentricity, concrete strength, and cave height in optimizing the design of PHC pile foundations for safety in complex geological settings. Full article

Hydroxyapatite (HAP) inserts minimize restoration contraction by constituting a major part of the restoration; however, their effect on the relaxation of tooth tissues has not been previously tested. Finite element analysis was employed to estimate stress and displacement when HAP inserts with a thickness of 1.7 mm or 4.7 mm and a diameter of 4.7 mm were used to substitute for dentin. The volumetric contraction of the composite during polymerization, simulated through steady-state heat transfer analysis, yielded a contraction rate of 3.7%. Descriptive statistics revealed that the incorporation of HAP inserts reduced the displacement of dentin, enamel, and restoration caused by contraction by 44.4% to 66.7%, while maximal stress was reduced by 8.1% to 52%. Subsequent loading on the occlusal tooth surface showed that displacement values decreased by 12.1% to 33.3%, while maximum von Mises stress in enamel decreased by 32.8% to 40.6% with the use of HAP inserts. Although the maximum stress values in dentin were not significantly decreased (3% to 8.8%), the stress located at the bottom of the cavity was notably reduced, particularly in deep cavities at root canal entrances. The use of HAP inserts in restorative dentistry provides benefits for the preservation of prepared teeth, especially in preventing irreparable vertical root fractures of endodontically treated teeth. Full article

Accurate ocean tide models are required to remove tidal loading effects in geophysical research. Beyond a mere intercomparison, the accuracy of eight modern global models (DTU10, EOT20, FES2014b, FES2022b, GOT4.10c, HAMTIDE11a, OSU12, TPXO10-atlas-v2) and one regional model (NAO99Jb) was assessed in the eastern China marginal seas (ECMSs) using geodetic measurements. This involved rigorous comparisons with the tidal constant measurements at 65 tide gauges and with the GPS-measured M₂ vertical ocean tide loading (OTL) displacements at 22 sites. The selected models showed significant disagreements close to the coasts of eastern China and the western Korean Peninsula, where the largest discrepancy for the M₂ constituent could exceed 30 cm. However, EOT20 and FES2014b provided relatively close results, differing by only about 15 cm in Hangzhou Bay. EOT20 compared more favourably than the others to the tidal constant measurements, with a root sum square (RSS) of 11.1 cm, and to the GPS-measured M₂ vertical OTL displacements, with a root mean square (RMS) of 0.49 mm. In addition, to differentiate between ocean tide models with subtle discrepancies when comparing them with the OTL measurements, consideration of the asthenospheric anelasticity effect was necessary. Full article

This paper establishes a physical model for the non-contact rotary screen coating process based on a spacecraft structural plate and proposes a theoretical expression for the adhesive thickness of the non-contact rotary screen coating. The thickness of the adhesive is a critical factor influencing the quality of the optical solar reflector (OSR) adhesion. The thickness of the adhesive layer depends on the equivalent fluid height and the ratio of the fluid flow rate to the squeegee speed below the squeegee. When the screen and fluid remain constant, the fluid flow rate below the squeegee depends on the pressure at the tip of the squeegee. The pressure is also a function related to the deformation characteristics and speed of the squeegee. Based on the actual geometric shape of the wedge-shaped squeegee, the analytical expression for the vertical displacement of the squeegee is obtained as the actual boundary of the flow field. The analytical expression for the deformation angle of the squeegee is used to solve the contact length between the squeegee and the rotary screen. It reduces the calculation difficulty compared with the previous method. Based on the theory of rheology and fluid mechanics, the velocity distribution of the fluid under the squeegee and the expression of the dynamic pressure at the tip of the squeegee were obtained. The dynamic pressure at the tip of the squeegee is a key factor for the adhesive to pass through the rotary screen. According to the continuity equation of the fluid, the theoretical thickness expression of the non-contact rotary screen coating is obtained. The simulation and experimental results show that the variation trend of coating thickness with the influence of variables is consistent. Experimental and simulation errors compared to theoretical values are less than 5%, which proves the rationality of the theoretical expression of the non-contact rotary screen coating thickness under the condition of considering the actual squeegee deformation. The existence of differences proves that a small part of the colloid remains on the rotary screen during the colloid transfer process. The expression parameterizes the rotary screen coating model and provides a theoretical basis for the design of automatic coating equipment. Full article

Mechanical construction has gradually been applied in cross passages of metro lines, but more mechanical mechanisms should be revealed. The section between Jingrong Street Station and Kunjia Road Station in Suzhou Metro Line 11 adopts a mechanical construction method to construct a cross passage. A novel flat-face cutterhead, which is different from curved cutter head is first used to cut and break the main tunnel in construction of cross passage. Based on the background of practical engineering, the finite element method was applied to simulate the breaking process of the main tunnel to explore the dynamic variation in the mechanical response of the segments cut by the flat-face cutterhead. The results indicate that the maximum vertical displacement caused by cutting mainly concentrates on the top of the fully cut rings. The maximum horizontal displacement occurs at the waist on the side of the tunnel portal in the semi-cut rings. The axial force level inside both types of segment rings reaches its peak after the tunnel is formed. The maximum axial force exists at the bottom and top of the fully cut ring and semi-cut ring, respectively. The change in the displacement around the portal is not substantial before the third stage, and it begins to increase significantly from the moment the concrete at the portal is penetrated. The existence of the pre-support system effectively controls the displacement of the third and fourth fully cut rings. Emphasis should be placed on reinforcing the soil near the top and waist of the second to fifth rings. The findings demonstrate that the application of flat-face cutterhead in mechanical construction of cross passages is safe, reliable, and efficient, and can provide valuable suggestions for further cutting parameters and soil reinforcement as well. Full article