Search Results (43)

This paper addresses the critical challenge of selecting suitable pile foundations in port engineering by systematically investigating the axial bearing behavior of large-diameter steel pipe piles and prestressed high-strength concrete (PHC) piles. The study integrates both numerical simulations and field tests within the context of the Yancheng Dafeng Port Security Facilities Project. A self-balanced static load numerical model for PHC piles was developed using Plaxis 3D, enabling the simulation of load-displacement responses, axial force transfer, and side resistance distribution. The accuracy of the model was verified through a comparison with field static load test data. With the verified model parameters, the internal force distribution of steel pipe piles was analysed by modifying material properties and adjusting boundary conditions. A comparative analysis of the two pile types was conducted under identical working conditions. The results reveal that the ultimate bearing capacities of the 1# steel pipe pile and the 2# PHC pile are 6734 kN and 6788 kN, respectively. Despite the PHC pile having a 20% larger diameter, its ultimate bearing capacity is comparable to that of the steel pipe pile, suggesting a more efficient utilisation of material strength in the latter. Further numerical simulations indicate that, under the same working conditions, the ultimate bearing capacity of the steel pipe pile exceeds that of the PHC pile by 18.43%. Additionally, the axial force distribution along the steel pipe pile shaft is more uniform, and side resistance is mobilised more effectively. The reduction in side resistance caused by construction disturbances, combined with the slenderness ratio (L/D = 41.7) of the PHC pile, results in 33.87% of the pile’s total bearing capacity being attributed to tip resistance. The findings of this study provide crucial insights into the selection of optimal pile types for terminal foundations, considering factors such as bearing capacity, environmental conditions, and economic viability. Full article

While a large diameter is critical for maintaining water delivery efficiency in prestressed concrete cylinder pipes (PCCPs), excessive weight fundamentally limits their practical application. This study proposes a weight reduction strategy through material optimization and structural redesign. A full-scale experimental model of 2.8 m inner diameter PCCP was used to validate the finite element analysis method. Comparative numerical models were established to analyze strain/stress distribution in mortar coatings when using ultra-high-performance concrete (UHPC) versus conventional concrete cores. The key findings reveal that UHPC implementation reduces maximum coating strain by 20–30% compared to its conventional concrete counterparts. Multivariate linear regression analysis yielded a predictive formula that explicitly correlates the elastic modulus of the concrete core, core thickness, and mortar stress. This relationship permits the direct optimization of core thickness reductions according to the elastic modulus characteristics of UHPC materials. Verification through two case studies demonstrated a 25–35% core thickness reduction compared to the Chinese standard specifications while maintaining structural integrity, corresponding to an 18–22% total weight reduction. The proposed methodology successfully resolves the inherent weight limitation of conventional PCCPs while achieving equivalent hydraulic capacity, providing an effective pathway for sustainable infrastructure development through material-efficient design. Full article

The accurate installation position of corrugated pipes is critical for ensuring the quality of prestressed concrete box girders. Given that these pipes can span up to 30 m and are deeply embedded within rebars, manual measurement is both labor-intensive and prone to errors. Meanwhile, automated recognition and measurement methods are hindered by high equipment costs and accuracy issues caused by rebar occlusion. To balance cost effectiveness and measurement accuracy, this paper proposes a method that utilizes an RGB-D camera and deep learning. Firstly, an optimal registration scheme is selected to generate complete point cloud data of pipes from segmented data captured by an RGB-D camera. Next, semantic segmentation is applied to extract the characteristic features of the pipes. Finally, the center points from cross-sectional slices are extracted and curve-fitting is performed to recognize and measure the pipes. A test was conducted in a simulated precast factory environment to validate the proposed method. The results show that under the optimal fitting scheme (BP neural network with circle fitting constraint), the average measurement errors for the three pipes are 2.2 mm, 1.4 mm, and 1.6 mm, with Maximum Errors of −5.8 mm, −4.2 mm, and −5.7 mm, respectively, meeting the standard requirements. The proposed method can accurately locate the pipes, offering a new technical pathway for the automated recognition and measurement of pipes in prefabricated construction. Full article

The failure accidents of prestressed concrete cylinder pipe (PCCP) seriously affect the economic feasibility of the construction site. The traditional method of needing to stop construction for pipe inspection is time-consuming and laborious. This paper studies the PCCP broken wire identification algorithm based on deep learning. A PCCP wire-breaking test platform was built; the Distributed Fiber Acoustic Sensing Monitoring System (DAS) monitors wire-breakage events in DN4000mm PCCPs buried underground. The collected broken wire signal creates a time-frequency spectrum diagram dataset of the simulated broken wire signal through continuous wavelet transform (CWT). Considering the location of equipment limitations, based on the YOLOv5 algorithm, a lightweight algorithm, YOLOv5-Break is proposed for broken wire monitoring. Firstly, MobileNetV3 is used to replace the YOLOv5 network backbone, and Dynamic Conv is used to replace Conv in C3 to reduce redundant computation and memory access; the coordinate attention mechanism is integrated into the C3 module to make the algorithm pay more attention to location information; at the same time, CIOU is replaced by Focal_EIoU to make the algorithm pay more attention to high-quality samples and balance the uneven problem of complex and easy examples. The YOLOv5-Break algorithm achieves a mAP of 97.72% on the self-built broken wire dataset, outperforming YOLOv8, YOLOv9, and YOLOv10. Notably, YOLOv5-Break reduces the model weight to 7.74 MB, 46.25% smaller than YOLOv5 and significantly lighter than YOLOv8s and YOLOv9s. With a computational cost of 8.3 GFLOPs, YOLOv5-Break is 71.0% and 78.5% more efficient than YOLOv8s and YOLOv9s. It can be seen that the lightweight algorithm YOLOv5-Break proposed in this article simplifies the algorithm without losing accuracy. Moreover, the lightweight algorithm does not require high hardware computing power and can be better arranged in the PCCP broken wire monitoring system. Full article

The disturbance generated during the pile installation process increased the compressibility of the soil between the piles, thereby causing additional settlement of the composite foundation. This study was conducted against the background of a highway soft foundation treatment project in Zhongshan. Before and after the installation of cement mixing piles (CMP) and pre-stressed high-strength concrete pipe pile (PHC), a piezocone penetration test (CPTU) was applied to assess the soil between the piles and quantify the disturbance. Based on this, the settlement of the composite foundation was predicted using the stress modified method and finite element method (FEM). The results indicate that under low embankment load (<2.5 m), the installation of PHC piles reduces the compression modulus of the soil between the piles by approximately 30%, while CMP results in a reduction of about 10%. Disturbance settlement from CMP and PHC piles accounts for approximately 3–10% and 17–28% of the total settlement, respectively. This impact diminishes with the increase of embankment load. Full article

Non-autoclaved pre-stressed high-strength rubber-modified concrete (NA-PHRC) pipe piles were developed to address the high energy consumption and brittleness of existing pre-stressed high-strength concrete (PHC) pipe piles. The comparative flexural test results showed that the deformation capacity of NA-PHRC pipe piles improved, which was correlated with the rubber content. However, both the cracking moment and the ultimate moment decreased. When the rubber content is 5% and 10%, the cracking moment decreases by 3.85% and 7.69%, respectively, while the ultimate moment decreases by 3.75% and 7.28%. Additionally, the theoretical calculation results of the influence of rubber on the cracking and ultimate moments were consistent with the experimental results. Thus, this innovative NA-PHRC pipe pile can be applied in environments that require high durability. Full article

The implementation of large-diameter flood diversion pipelines in urban areas serves as an effective strategy to address urban waterlogging issues, which can enhance the resilience of cities to a certain extent against extreme precipitation events. This case study delineates the Zhengzhou Jinshui River flood diversion project, which employs the ultra-large-buried jacking prestressed concrete cylinder pipe (JPCCP), offering a summary and analysis of the pipe design and construction technologies employed in the JPCCP project within collapsible loess stratum, and the study also analyzes the pull-back scheme of the incident involving the front-end sinking of the machine head. Through on-site monitoring experiments, the variation patterns of contact pressure and slurry pressure of large-diameter JPCCPs were analyzed. The results demonstrate that the trends in contact pressure and slurry pressure exhibit a general consistency. During the jacking process, the pressure around the pipe can be categorized into three distinct phases based on grouting frequency or pressure, with notable variations in the pipe–soil–slurry contact state. The difference between the contact pressure and slurry pressure (termed as effective soil pressure) serves as a more accurate method for determining the pipe’s operational state. Moreover, the effective earth pressure at the pipe top demonstrates a higher degree of consistency with the calculation results prescribed by the standards ATV A161 and ASCE 27. Full article

The pre-stressed high-strength concrete (PHC) nodular pile is a type of PHC pile with a variable cross-section of the pile shaft, and it has normally been applied in ground treatment projects in recent years. The PHC nodular pile shaft consists of nodules, which introduce differences for the load transfer mechanism of the PHC nodular pile compared to the conventional PHC pipe pile. In this paper, the load transfer mechanism and influencing factors of the bearing capacity of the PHC nodular pile were investigated based on a group of field tests and numerical simulations. The following conclusions were obtained based on the analysis of the field test and simulation results: the nodules along the pile could effectively increase the ultimate capacity of the PHC nodular pile, and the field test results showed that the ultimate capacity of 450 (500) mm PHC nodular piles was about 1.23–1.38 times of the 450 mm PHC pipe pile after being cured for 40 days, which can be used for the design of PHC nodular pile. The simulation results showed that the bearing capacity of the PHC nodular pile would decrease with the increase in nodular spacing and nodular length along the pile shaft, while increasing with the increase in nodular diameter, and the diameter of the nodule can be increased moderately to improve the ultimate capacity of the PHC nodular pile. Full article

Uniform support from the surrounding soil is important for maintaining the stable operation of buried pipelines. For segmented prestressed concrete cylinder pipe (PCCP), localized soil voids around the joint due to leakage or engineering activities make the pipe unsupported partially and threaten its integrity and strength. In this paper, the impact of a localized soil void on a pipe joint is qualitatively assessed using a beam-on-elastic-spring approximation model. It further provides quantitative analysis through a nonlinear finite element (FE) model of PCCPs and the surrounding soil. The derived algebraic solutions indicate that a unilateral local void induces shear force and rotation at the joint, whereas shear force becomes negligible when the void spans the joint, leading to increased rotation. Moreover, the rotation angle shows a positive correlation with soil load and a negative correlation with pipe diameter. Numerical analysis reveals that void elongation along the pipe length has a more pronounced effect on structural response than void depth and angle. When the void length reaches 2.5 m, the maximum principal stress on the mortar layer of the PCCP increases approximately eight-fold compared to the scenario without voids. Due to the rigidity and safety factor of the PCCP, small voids in the bedding typically do not cause immediate pipe damage or joint leakage; however, they can significantly alter the stress distribution within both the pipe and surrounding soil. As the void develops, the soil may collapse and compromise support, leading to additional secondary disaster risks and potential threats to pipeline safety. This research emphasizes the importance of effective pipe-soil interactions and provides theoretical insights for developing repair strategies for PCCP. Full article

At Cracow University of Technology, attempts were made to develop national truck scale platforms with a capacity of 60 tons, made from prestressed concrete. For this work, we designed slabs partially prestressed with unbonded tendons featuring a cross-section of 1.00 × 0.28 m and a span of 5.94 m. To reduce the weight of the slabs, four channels made from commonly used ø110 × 2.2 mm PVC pipes were used. In this way, we created post-tensioned hollow-core slabs. Due to the unpredictable behavior of slabs operating in a cracked state under a repetitive load, two slabs were subjected to cyclic loads amounting to 1,000,000 cycles with different load values. This paper presents the basic design principles and design details of the slabs, as well as the methodology and results of the research conducted. Lastly, we provide appropriate conclusions directed at further optimizing the slabs. Full article

When constructing hollow prestressed high-strength concrete (PHC) pipe piles in soft soil foundations, the generation and dissipation of pore water pressure can induce negative friction on the pile. This phenomenon increases the settlement of the pile foundation and, in severe cases, can lead to pile deflection and flotation. To further investigate the development characteristics of pore water pressure during PHC hollow pipe pile driving in soft soil, this study combined existing theories and numerical models to analyze the generation and influence areas of pore water pressure. Field tests were conducted at three different sites: an untreated site, a surcharge preloading site, and a site treated with cement mixing piles and well dewatering. These tests monitored and analyzed the horizontal and vertical development and behavior of pore water pressure during pile driving at each site. The results indicate that during the pile driving process, when the horizontal distance from the pile center is 3d and 9d, the peak values of the excess pore water pressure in the site treated with cement mixing piles and well dewatering are 117 kPa and 100 kPa. After pile driving is completed, they decrease to 50 kPa and 48 kPa, respectively. The peak values of excess pore water pressure in the surcharge preloading site are 122 kPa and 97 kPa, and after pile driving, they decreased to 80 kPa and 21 kPa, respectively. The peak values of excess pore water pressure in untreated sites are 140 kPa and 121 kPa; after pile driving, they decreased to 82 kPa and 60 kPa, respectively. Pore water pressure increases with the depth of pile driving and decreases with distance from the pile driving location. The peak pore water pressure and dissipation rate during construction were found to be higher at the untreated site compared to the other two sites. Therefore, during pile sinking in soft soil foundations, dewatering and driving drainage boards are effective methods for reducing pore water pressure and accelerating its dissipation. These findings provide a theoretical basis and technical support for ensuring the safety of engineering constructions. Full article

Drilling with prestressed concrete (DPC) pipe pile is a nonsqueezing pile sinking technology, employing drilling, simultaneous pile sinking, a pipe pile protection wall, and pile side grouting. The unloading induced by drilling, the pipe pile supporting effect, and the dissipation of the negative excess pore-water pressure after pile sinking, all of which have significant effects on the recovery of soil pressure on the pile side, are the main concerns of this study, which aim to establish a method to reasonably evaluate the timing selection of pile side grouting. The theoretical solutions for characterizing the unloading and dissipation of the negative excess pore-water pressure are presented based on the cylindrical cavity contraction model and the separated variable method. By inverse-analyzing the measured initial pore pressure change data from borehole unloading, initial soil pressures on the pile side of each soil layer are determined using the presented theoretical solutions. Then, the presented theoretical solutions were verified through a comparative analysis with the corresponding measured results. Moreover, by introducing time-dependent coefficients α_t1 and α_t2 to characterize the pore pressure dissipation and rheology effects, the effects of the negative excess pore-water pressure dissipation on the pile-side soil pressure recovery are discussed in detail. Full article

Prestressed pipe piles are common concrete components characterized by dense concrete structures and favorable mechanical properties, and thus, extensively used as coastal soft soil foundations. However, their durability in harsh environments has not been fully clarified. In this study, leachate from an actual landfill site was collected from the east coast of China as the corrosive medium, and the corrosion process was accelerated by electrifying prestressed pipe piles. The results demonstrated that the concentration of chloride ions in the concrete of the prestressed pile increased with the increase in corrosion time. Moreover, the experimental corrosion of these prestressed piles in the drying–wetting cycle proved to be the most severe. However, a protective layer of epoxy resin coating can effectively inhibit the diffusion of chloride ions into the interior of the piles. The final theoretical corrosion amounts of the piles were 1.55 kg, 1.20 kg, and 1.64 kg under immersion, epoxy resin protection, and a drying–wetting cycle environment. The application of epoxy resin reduced chloride penetration by 22.6%, and the drying–wetting cycle increased chloride penetration by 5.8%, respectively, with corresponding corrosion potentials following similar patterns. The actual corrosion depth of the welding seam was 3.20 mm, and there was a large corrosion allowance compared with the requirement (6.53 mm) for the ultimate bending moment. In summary, these prestressed piles exhibited good durability in a leachate environment. Full article

To investigate the load-carrying performance of the nodes between tubular piles and bearing platforms, low circumferential reciprocating load foot-scale tests were performed on two truncated PHC B 600 130 tubular piles. The development law of node destruction was explored. The test results revealed that under the action of tensile–bending–shear loading, the bearing concrete in the node area buckled and was damaged, and an articulation point was formed. When the embedment depth increased from 200 mm to 300 mm, the ultimate bearing capacities of the positive and negative nodes increased by 57.60% and 54.60%, respectively. Numerical simulation was used to analyze the bearing capacities of nodes with different types and embedment depths. Formulas for the bearing capacity of the nodes were proposed. Furthermore, two preferred node types were proposed as follows: pipe pile core-filled longitudinal reinforcement anchored to the bearing node and pipe pile body longitudinal reinforcement anchored to the bearing node + pipe pile core-filled longitudinal reinforcement anchored to the bearing node, with preferred embedment depths of 350 mm and 200 mm, respectively. Full article

The quality of grouting in pre-stressed pipelines plays a critical role in ensuring the safety and durability of pre-stressed concrete bridges. In this study, the transmission wave method was proposed as a means to assess the quality of grouting in pre-stressed pipelines. The ABAQUS finite element simulation (FE simulation) method was used to study the propagation of hammer stress waves in pre-stressed pipes. A full-scale test was conducted to verify the numerical simulation using the AGI-BWG instrument system developed to detect the quality of grouting. The results show that the propagation speed of transmitted waves increases and the frequency shifts towards higher frequencies with an increase in void length within pre-stressed pipelines. This research suggests that the propagation velocity of elastic waves in pre-stressed pipelines serves as a key indicator of grouting quality. The transmission wave method, based on hammer signals, proves to be an effective tool for detecting the quality of grouting in pre-stressed pipelines. Full article