Three-dimensional Numerical Analysis Research Articles

Research on the Correction of Soil Pressure Distribution Pattern in Circular Working Wells in Soft Soil Areas

This paper investigates the distribution characteristics of earth pressure on circular caisson foundations in soft soil areas based on practical engineering considerations. Utilizing a three-dimensional numerical analysis model and a displacement-based method for earth pressure calculation, the lateral earth pressure on the retaining structure is examined. Adjustments are made to the distribution pattern of earth pressure on circular caisson foundations in soft soil areas. The study demonstrates that the radius of the caisson significantly influences the spatial distribution of soil pressure. Additionally, empirical formulas for the depth and radius of the reduction in soil pressure around circular caisson foundations are obtained through the research. Comparative analysis reveals that the modified earth pressure planar foundation beam method, which accounts for the arching effect, is simpler, features more mature parameter selection, and is more cost-effective than the three-dimensional finite element method. In comparison to the standard planar elastic foundation beam method for earth pressure, it aligns more closely with the actual direction of displacement.

Three-Dimensional Numerical Field Analysis in Transformers to Identify Losses in Tape Wound Cores.

To find the total core losses in 1-phase medium-frequency transformers, a 3D numerical field analysis was carried out. The proposed numerical modeling was based on the extended iterative homogenization method (IHM) developed by the authors. The achieved calculation results were validated by the corresponding values obtained experimentally, and a reasonably close agreement was obtained.

Three-Dimensional Numerical Analysis of Static and Cyclic Pull-out Response of Plate Anchors in Reinforced Soft Clay

Three-Dimensional Numerical Analysis of Static and Cyclic Pull-out Response of Plate Anchors in Reinforced Soft Clay

Numerical parametric study of embedded geosynthetic-reinforced soil abutment

Three-dimensional numerical analysis was conducted to investigate the performance of embedded geosynthetic-reinforced soil abutments. The numerical model was validated using field-monitoring data. A parametric study was conducted to investigate the key factors affecting the performance of the embedded abutment under the working conditions, including the pile offset distance, pile diameter, pile spacing, and bridge load. The piles exhibited a retaining rather than a pushing effect in these cases due to the relatively high stiffness and negative skin friction of the piles, thus reducing the loads exerted on the facing wall. The lateral displacement of the facing wall significantly increased as the pile offset distance decreased mainly due to the reduced anchor length of the reinforcement and enhanced retaining effect of the piles. As the pile diameter increases, the deflection of the facing wall is constrained by factors such as increased bearing width, limited displacement, and enhanced retention effect of thepiles. This is an efficient way to increase the pile density near the abutment centerline to control thedeformation of the facing wall. An increase in the vertical bridge load resulted in a decrease in negative skin friction, leading to increased foundation settlement and lateral displacement of the facing wall.

Time-dependent performance of large piled raft in clayey soil

In this study, three-dimensional numerical analysis has been performed to comprehend the time-dependent behavior of large piled rafts founded in saturated clayey soil, explicitly for the time of superstructure construction and post-construction up to the end of soil consolidation. The performance under different construction times for the corresponding unpiled raft and the piled raft with uniform pile length configuration of varying pile number, spacing, and length have been examined and then compared with that of non-uniform length configuration for the same total pile length. The dissipation of excess pore water pressure, average settlement, and differential settlement are presented and discussed in detail. A quicker dissipation rate of excess pore pressure is noted with either fewer piles, wider pile spacing, or shorter-length piles. An increase in construction time results in a lesser total average settlement at the end of consolidation. The piled raft with uniform pile length configuration shows a higher differential settlement than the unpiled raft. However, by adopting a suitable non-uniform length configuration, negligible differential settlement, higher load-carrying capacity, and a significant reduction in pile material volume can be achieved. Predictive expressions have been proposed to estimate the average and differential settlements of piled raft with uniform length configuration.

Optimizing ground improvement with encased stone columns: a 3D numerical analysis in very soft clay

Purpose This study aims to investigate the behavior of different types of stone columns, including the short and floating columns, as well as the ordinary and the geosynthetic encased stone columns (OSC and GESC). The effectiveness of the geosynthetic encasement and the impact of the installation using the lateral expansion method on the column performance is evaluated through a three-dimensional (3D) unit cell numerical analysis. Design/methodology/approach A full 3D numerical analysis is carried out using the explicit finite element code PLAXIS 3D to examine the installation influence on settlement reduction (ß), lateral displacement (Ux) and vertical displacement (Uz) relative to different values of lateral expansion of the column (0% to 15%). Findings The findings demonstrate the superior performance of GESC, particularly short columns outperforming floating counterparts. This enhanced performance is attributed to the combined effects of geosynthetic encasement and increased lateral expansion. Notably, these strategies contribute significantly to decreasing lateral displacement (Ux) at the column’s edge and reducing vertical displacement (Uz) under the rigid footing. Originality/value In contrast to previous studies that examined the installation effect of OSC contexts, this paper presents a comprehensive investigation into the effect of geosynthetic encasement and the installation effects using the lateral expansion method in very soft soil, using 3D numerical simulation. The study emphasizes the significance of the consideration of geosynthetic encasement and lateral expansion of the column during the design process to enhance column performance.

Three-Dimensional Numerical Analysis of Large-Scale Horizontal Square Anchors in Geogrid-Reinforced Sand

This paper presents a comprehensive three-dimensional numerical investigation of horizontal square anchors embedded in geogrid-reinforced sand. Prior experimental studies have demonstrated notable enhancements in anchor uplift capacity when placed below geogrid reinforcement in soil. However, these results are limited to small anchor plates tested in laboratory conditions with over-reinforced sand. In contrast, this study focuses on large field-scale anchors and explores the influence of anchor width, embedment depth, reinforcement size, stiffness, and tensile strength on uplift capacity. The findings reveal that the optimal size for geogrid reinforcement is three times the anchor width. A diminishing improvement in uplift capacity with increasing anchor width was observed. Additionally, deeper anchor embedment reduces the uplift capacity improvement in geogrid-reinforced sand. The geogrid reinforcement is found to be more efficient in the case of shallow anchors placed in loose sand. The major contribution of this paper lies in the response analysis of large anchors and providing a better understanding of the uplift mechanism in geogrid-reinforced sand.

Three-Dimensional Numerical Analysis of Embankment Overlying Geotextile-Encased Columns with Granular Platform

Three-Dimensional Numerical Analysis of Embankment Overlying Geotextile-Encased Columns with Granular Platform

Physical and Finite Element Models for Determining the Capacity and Failure Mechanism of Helical Piles Placed in Weak Soil

The foundations of particular engineering structures, including marine and jetty structures, mooring systems for submerged platforms or those on the ocean surface, and transmission towers, are subjected to various external loads including compression, uplift, and lateral loads. In such cases, to improve the soil resistance below foundations, pile foundations such as helical piles, anchored piles, and batter piles are commonly preferred, depending on the in situ conditions. Helical piles, increasingly used as an alternative foundation to conventional piles, are placed in the soil body by rotating with torque. This paper deals with the contribution of a helical pile in improving loose sandy soil, and the main purpose is to study the effect of the helix-buried depth on the load-bearing capacity and failure mechanism. The investigated variables include the distance between helixes, the number of helixes, and the diameter of the upper helix. Physical model tests were conducted, and two- and three-dimensional numerical analyses were performed by using the finite element method with an advanced soil model to illustrate the failure mechanisms of helical piles. The aim was to reveal the efficiency of the finite element method in modelling helical piles placed in weak sandy soil. A simplified linear geometry for helixes was established in a two-dimensional finite element model whereas a real geometry for helixes, which was a more realistic approach, was created in a three-dimensional finite element model. The results show that the three-dimensional model indicates better agreement with the physical model compared to the two-dimensional model, and all investigated variables highly affect the load-bearing capacity of helical piles.

Fast electrokinetic mixing in microflows with different electrical conductivities

This work provides a novel three-dimensional numerical analysis of electrokinetic mixing in microflows with different electrical conductivities. Our study examines ferrofluid and water co-flow mixing quantitatively, which has been overlooked in previous micromixers based on electrokinetic instabilities. This has become possible by considering the actual diffusivity of ferrofluid. The findings reveal that thinner channels exhibit stronger suppression of instability due to the pronounced effect of walls on the flow, emphasizing the importance of 3D simulation for shallow channels. Additionally, increasing the electric field intensity was found to have dual opposing effects on instabilities and electrolyte mixing. It enhances the body force and instabilities, improving mixing, but also accelerates flow velocity, reducing fluid residence time and leading to weaker mixing of the flows. A notable observation was a decrease in the mixing index with the augmentation of electric field intensity; for a channel with H = 200 µm, the mixing index reduced by approximately 13% when the electric field strength was increased from 179 to 210 V/cm.

Failure mode of the hazardous Diaozui rock mass of the Qutang Gorge in the Three Gorges Reservoir area based on a three-dimensional numerical analysis

Failure mode of the hazardous Diaozui rock mass of the Qutang Gorge in the Three Gorges Reservoir area based on a three-dimensional numerical analysis

Load Carrying Mechanism of Geocell Reinforced Embankment on Soft Soil

This paper investigates the influence of geocell reinforcement on the load carrying mechanism of embankments over soft soil. Using a geocell mattress beneath an embankment on soft soil, the size of the rupture zone in the foundation bed is found to have increased significantly, leading to increase in the mobilized shear resistance, and giving rise to enhanced bearing capacity. While the unreinforced embankment, owing to differential settlements, tends to crack and disintegrate, the geocell reinforced embankment continues to behave as a monolith up to a high surcharge pressure/fill height. The performance improvement tends to increase with increase in height of the geocell mattress. Strain variation in the geocell mattress indicates that its reinforcing efficacy is the largest at the central crest region of the embankment and decreases toward the toe. As the geocell mattress behaves as a semirigid slab, when it is present, the stress dispersion angle tends to increase significantly. Considering the stress dispersion zone as an equivalent rigid footing, the bearing capacity of unreinforced and geocell reinforced embankments are analyzed. The predicted bearing capacities are found to be in close agreement with the experimentally observed ones. Three-dimensional numerical analyses indicate that the pressure–settlement behavior of the embankments observed in the model tests is reproduced at large scale.

Anisotropic flow physics in diamond microchannels: Design implications for microfluidic rectifiers handling Newtonian fluids

The study explores anisotropic flow behavior in microchannels, which is crucial for advancing microfluidic rectifiers. Specifically, the investigation focuses on the directional flow behavior of Newtonian fluids within diamond-shaped microchannels, a topology holding significant promise across various disciplines. Unlike non-Newtonian fluids, Newtonian fluids lack inherent directional traits, needing high Reynolds numbers for inertial effects necessary for effective rectification in asymmetric flow structures. High Reynolds numbers in microchannels are challenging, but diamond microchannels uniquely exhibit inertial effects even at low Reynolds numbers, yet their potential for designing rectifiers is largely unexplored. The study presents two unique asymmetric diamond microchannel designs and conducts thorough three-dimensional numerical analyses to assess fluid flow across different design parameters. Rectification is quantified through fluid diodicity, demonstrating that configurations with higher width and aspect ratios and shorter lengths produce significant rectification effects. Examining velocity profiles and flow resistances in both directions illustrates irreversible flow physics. Notably, the observed maximum diodicity for the proposed design reaches 1.61 for Newtonian fluids, surpassing most previous designs by 11%–40%. Quantitative relationships between flow resistances in both directions and design variables through regression analysis allow determining flow resistances within ±8% and fluid diodicity within ±7% and ±10%, respectively, based on constant flow rate and pressure drop. These correlations provide valuable insights for the initial design of microfluidic rectifiers using these configurations. The results offer essential guidance for effectively designing microfluidic rectifiers using diamond microchannels in various scientific applications.

Tunneling problems in weak rock conditions under shallow overburden and comparison between full-face excavation and sequence excavation methods

ABSTRACT The T8 tunnel was constructed within the scope of the Ankara – Sivas High-Speed Railway project. The tunnel route is formed completely by very weak and weak lithological units. The overburden decreases to 10 m, and the highest overburden thickness reaches up to 60 m. The tunnel is large with a 150 m2 excavation area and 14 m diameter. During the excavations in the section with an overburden thickness of 12 m, the supports failed, and the tunnel was completely collapsed. The purposes of the present study are to discuss the causes of the failure and engineering measures and to compare NATM and ADECO-RS methods with three-dimensional (3D) numerical analyses. Considering the mechanism of failure, extra engineering measures were proposed and the T8 tunnel was completed successfully. For the purpose of the study, a series of 3D numerical analyses were performed, and the results are discussed. The results obtained from the 3D numerical analyses showed that the ADECO-RS method yielded higher performance than the NATM method, for very weak and weak ground conditions (Category C).

Investigation of local flow and heat transfer of supercritical LNG in airfoil channels with different vortex generators using field synergy principle

Vortex generators（VGs） have gained significant attention as a potential technology for enhancing heat transfer. This study introduces a novel delta airfoil VG with the objective of improving the heat transfer efficiency of heat exchangers. The overall heat transfer performance of four types of printed circuit heat exchanger (PCHE) channels is evaluated using three-dimensional numerical analysis in this paper. These channels comprise of two VGs with different shapes and installations, along with NACA0024 airfoil fins. The delta winglet VG (DWVG), the delta airfoil VG (DAVG), and the delta airfoil staggered VG (DASVG) are the VGs used in the three PCHE channel configurations. The performance of the four PCHE flow channels is assessed using the dimensionless thermal enhancement factor (TEF). To investigate and explain the interaction between VGs and flow structure distribution as well as heat transfer, the secondary flow number Se and the field synergy principle are employed. The results show that the local field synergy angle of the channel with VGs is smaller than that of the non-VG baseline case, indicating the best enhanced heat transfer in the pseudo-critical region. Among the four cases, the DAVG exhibits the best hydrothermal performance, and the local heat transfer coefficient can be increased up to 120%, which aligns with the interpretation of the field synergy principle.

Seismic performance and vulnerability analysis for bifurcated tunnels in soft soil

This paper investigates the seismic performance of complex comprehensive interchange underground structures. As an example, the seismic performance of Nanjing underground bifurcated tunnels constructed in soft soil is analyzed. A three-dimensional (3D) numerical finite element analysis model is established considering soil-tunnel interaction to analyze the seismic response characteristics and failure mechanism of the bifurcated tunnels. The results show that the tunnel damage degree is closely associated with the deformation response, and that the inter-story drift ratio of the lower layer is significantly greater than that of the upper layer. The pushover analysis method is used to obtain the seismic performance curve of the tunnel, and inter-story drift ratio limits are defined. The IDA procedure is then used to conduct multiple non-linear dynamic time history analyses based on the 3D finite element model, and IDA curve clusters are drawn with peak ground acceleration (PGA) as the earthquake intensity measures and the peak inter-story drift ratio as the damage measures of tunnels. The corresponding IDA percentiles lines are calculated, and the seismic fragility curves of the bifurcated tunnels are established. The post-earthquake functional failure probability of the bifurcated tunnels is obtained under different seismic fortification performance level.

Analysis of Near-wall Coherent Structure of Spiral Flow in Circular Pipe Based on Large Eddy Simulation

Based on the large eddy simulation method, this study performed the three-dimensional transient numerical analysis of the near-wall flow field of the spiral flow in a circular pipe and applied the sub-grid model of the kinetic energy transport. The low-speed bands, streamwise vortices and hairpin vortices of the spiral flow in the near-wall region of the circular pipe are determined using the Q criterion. The ejection and sweeping of coherent structures are identified using the velocity vector of the near-wall region; moreover, the two methods of creating the hairpin vortices are established by the image time series. The results demonstrate that the development directions of the near-wall bands, streamwise vortices and hairpin vortices of the spiral flow in the circular pipe develop along the path of the spiral line. The average spanwise period of the low-speed bands in the near-wall region is approximately 120 wall units, the length is more than 900 wall units and the height is not more than 40 wall units. The separation distance of the streamwise vortices is about 119 wall units. It has a certain angle with the wall (approximately 22°). The average burst period of a hairpin vortices is less than 0.015 s.

Heat exchange characteristics of underground and pavement buried pipes for bridge deck heating conditions.

Geothermal energy is increasingly employed across diverse applications, with bridge deck snow melting emerging as a notable utilization scenario. In Jinan city, China, a project is underway to utilize ground source heat pumps (GSHPS) for heating bridges. However, essential operational parameters, including fluid medium, temperature, and heat exchange details, are currently lacking. This study addresses the thermal design challenges associated with ground heat exchangers (GHE) for bridge heating through a combination of numerical modeling and field experiments. Utilizing software Fluent, a refined three-dimensional multi-condition heat transfer numerical analysis was carried out. Field tests based on actual operating conditions were also conducted and the design parameters were verified. The results indicate that an inlet temperature of 5°C and an aqueous solution of ethylene glycol with a mass concentration of 35% as the heat exchange medium are suitable for the GSHPS in Jinan; Moreover, the influence of backfill material and operation time on the heat transfer efficiency was revealed and the suitable material with 10% bentonite and 90% SiO2 was suggested; Finally, based on the influence of the pipe spacing on the heating characteristics of bridge deck, the transition spacing of 0.2 m is given for the temperature response of the bridge deck. This comprehensive study contributes valuable insights through simulation and experimental analysis of the thermal environment variation, aiming to advance the development of GSHPS for bridge deck heating in Jinan, China.

Effect of curved anchor impellers on power consumption and hydrodynamic parameters of yield stress fluids (Bingham–Papanastasiou model) in stirred tanks

Abstract This study introduces a three-dimensional numerical analysis of the mixing yield stress fluid inside stirred vessels. The Bingham–Papanastasiou model predicts the yield stress behavior of the working fluid. The implications of a new anchor impeller design are investigated; it involves certain modifications to a typical anchor impeller’s blade. Different curved shapes replace the straight blade of a classical anchor. The flow pattern and energy consumed inside the stirred system for various geometrical configurations, Reynolds numbers (0.1, 1, 10, and 100), and Bingham numbers (1, 10, 100, and 500) have been investigated. According to the findings, introducing this new geometrical configuration gives a significant acceleration of flow pattern and extension of the well-mixed zone, as well as decreased power consumption ( Np {\rm{Np}} ). Three configurations were introduced to the mixing system: Case 1 is a standard anchor impeller, and Cases 2 and 3 are curved anchor impellers with two shapes different. Case 3 (helical design of blade) has been found to be the less power consumption case by five times, i.e., for Case 1 and Case 2, Np = 5 {\rm{Np}}=5 , whereas for Case 3, Np = 1 {\rm{Np}}=1 . Based on the results, it is evident that the configuration (Case 3) demonstrates a superior geometric design in enhancing mixing characteristics compared to the other configurations.

Retracted: Three-Dimensional Finite Element Numerical Simulation and Analysis of Solid-State Processing of Metal Material

Retracted: Three-Dimensional Finite Element Numerical Simulation and Analysis of Solid-State Processing of Metal Material