3D Numerical Analysis Research Articles

Stability Analysis of Unsupported Vertical Cuts in the Vadose Zone using 2D and 3D Numerical Methods

Evidence supporting the implementation of three-dimensional (3D) slope stability analysis in geotechnical engineering practice has been mounting since the nineteen-seventies. Current levels of computational power and its accessibility has allowed researchers to investigate the significance of the 3D numerical analysis output compared to conventional 2D limit equilibrium approach. This study compares results of stability analyses of unsupported vertical cuts in the vadose zone using both 2D (GeoStudio 2019 R2) and 3D (FLAC3D) software. Numerical analyses are carried out for various dimensions of unsupported vertical cuts excavated in an unsaturated glacial till. The findings from two different methods (i.e. 2D and 3D) and the limitations of 2D stability analysis are discussed.

Design and numerical analysis of an efficient H-Darrieus vertical-axis hydrokinetic turbine

Hydrokinetic turbines are one of the technological alternatives to generate and supply electricity for rural communities isolated from the national electrical grid with almost zero emission. The Darrieus turbine is one of the options that can be used as a hydrokinetic turbine due to its high power coefficient (Cp) and easy manufacture. In the present work, the design and hydrodynamic analysis of a Darrieus vertical-axis hydrokinetic turbine of 500 W was carried out. A free stream velocity of 1.5 m/s was used for the design of the blades. The diameter (D) and blade length (H) of the turbine were 1.5 m and 1.13 m, respectively. The blade profile used was NACA0025 with a chord length of 0.33 m and solidity () of 0.66. Two (2D) and three dimensional (3D) numerical analyses of the unsteady flow through the blades of the turbine were performed using ANSYS Fluent version 18.0, which is based on a Reynolds-Averaged Navier-Stokes (RANS) model. A transient 2D simulation was conducted for several tip speed ratios (TSR) using a k-ω Shear Stress Transport turbulence (SST) scheme. The optimal TSR was found to be around 1.75. Main hydrodynamic parameters, such as torque (T) and CP, were investigated. Additionally, 3 geometrical configurations of the turbine rotor were studied using a 3D numerical model in order to identify the best configuration with less Cp and T fluctuation. The maximum Cp average was 0.24 and the amplitude of Cp variation, near 0.24 for the turbine model with 3 blades of H equal to 1.13 m. On the other hand, for the turbine models with 6 and 9 blades of H equal to 0.565 m and 0.377 m, respectively, the maximum Cp averages were 0.51 and 0.55, respectively, and the amplitude of Cp variation, near 0.07 for the model with 6 blades and 0.17 for the model with 9 blades. This revealed that the hydrokinetic turbine with a geometrical configuration of 6 blades greatly improves the performance of the turbine due to this model has advantages compared to models with 3 and 9 blades, in terms of the reduction of their T curve fluctuation.

Dynamic Behavior of Track Bridge on Serviced Long-Span Road/Railway Bridge

In this study, we predicted the structural behavior of a track-bridge and a bridge based on the expected increases in future train speeds by modeling the Yeongjong Bridge (a part of the Incheon International Airport Expressway in Korea). To verify the train’s safe operation, we performed a three-dimensional (3D) numerical analysis using full-scale bridge modeling. The rail-girder interaction force generated at one end of the direct fixation track of Yeongjong Bridge during train operations was evaluated by taking field measurements of the vertical displacements of the rail and girder at the center and end of a track girder. We further compared our predictions with various field measurements to evaluate the dynamic behavior of the entire Yeongjong Bridge.

Crumbling of Amatrice clock tower during 2016 Central Italy seismic sequence: Advanced numerical insights

The dynamic behaviour and the seismic vulnerability of the ancient civic tower of Amatrice, dramatically damaged by the last shocks sequence of 2016 that occurred in Central Italy, have been studied in this paper by means of advanced 3D numerical analyses with the Discrete Element Method (DEM). Thus, a discontinuous approach has been used to assess the dynamic properties and the vulnerability of the masonry structure, through large deformations regulated by the Signorini’s law, concerning the impenetrability between the rigid bodies, and by the Coulomb’s law, regarding the dry-friction model. Afterward, different values have been assigned to the friction coefficient of the models and real seismic shocks have been applied in the nonlinear analyses. The major purpose of this study is to highlight that relevant data on the real structural behaviour of historical masonry can be provided through advanced numerical analyses. The comparison between the results of the numerical simulation and the survey of the existing crack pattern of the bell tower permitted to validate the approach used. Finally, from the results and conclusions of this case study, it is possible to affirm that the used methodology can be applied to a wide variety of historical masonry structure in Europe.

Comparison between Analytical Method and Numerical Model for Footings on Soft Clay Supported by Stone Columns

The increase in population in many locations and the value of land has increased significantly. This has made the use of all areas including soft problematic soils inevitable. Due to the lack of bearing capacity of these soils, different methods of soil improvement techniques such as stone columns are used. In this study, four different analytical methods published before are briefly motioned. Also, three-dimensional (3D) numerical analyses were carried out on a stone column under footing on the soft clay soil. The main point of the current paper is to make a comparison between a numerical model and different analytical methods to represent a footing on the soft clay soil reinforced by a group of stone columns.

Experimental and numerical study on square anchor plate groups in geogrid reinforced sand

The paper investigates the behaviour of groups of horizontal square anchor plates in geogrid-reinforced sand using laboratory model tests. The optimum spacing for two anchor plates in unreinforced sand is 3.4 times the anchor width. The unreinforced groups of anchor plates show a clear failure at a displacement of about 5% of the anchor width, whereas this value increases to more than 45% for reinforced groups along with a two-fold increase in uplift capacity. The optimum width and length of the geogrid reinforcement for groups of two anchors is found to be 5 and 9.4 times the width of the anchor plate, respectively. The performance improvement for isolated anchor plates is found to be maximum and gradually reduces with an increase in the number of plates; however, this reduction is much less in groups of two to four. Therefore, the results obtained from the model tests for reinforced groups of two to four anchor plates can be conveniently used to extrapolate the uplift capacity of multiple anchor plate systems in a reinforced soil mass. The model test results show a reasonably good agreement with the three-dimensional (3D) numerical analysis results.

Investigation of effects of different construction sequences on settlement and load transfer mechanism of single pile due to twin stacked tunnelling

Construction of tunnels in urban cities may induce excessive settlement and tilting of nearby existing pile foundations. Various studies reported in the literature have investigated the tunnel-soil-pile interaction by means of field monitoring, centrifuge and numerical modelling, but the influence of construction sequence of twin stacked tunnelling on an existing pile is seldom reported in the literature. This paper presents a 3D coupled-consolidation numerical parametric analysis to understand settlement and load transfer mechanism in single pile due to twin stacked tunnelling with different construction sequences in stiff saturated clay. To accurately capture the tunnelling induced ground deformation, path- and strain-dependent soil stiffness at small strains were taken into account in each numerical analysis, by adopting an advanced hypoplastic clay model coupled with the inter-granular strain formulation. Twin stacked tunnelling was simulated one after the other with the first tunnel excavated near the mid-depth of the pile shift and the second either next to the toe of the pile (case ST) or below the pile (case SB). In addition, two more analyses were performed with change of construction sequence of twin stacked tunnels (i.e. cases TS and BS). The first tunnel was excavated either near the pile toe (case TS) or below the pile (case BS) and second tunnel near the mid-depth of the pile shaft. The different construction sequence of twin stacked tunnels at different depth had a substantial effect on induced pile deflection and settlement. In contrast, no significant effect was found on load transfer mechanism in the pile due to the change in construction sequence of tunnels.

Numerical analyses of an experimental excavation supported by panels of lime-cement columns

The influence of ground improvement with panels of overlapping lime-cement columns on the behavior of a braced excavation loaded to failure has been investigated using 3D numerical analyses and the results are compared with an experimental full-scale failure test. The analyses reveal that stress-induced strength anisotropy of lime-cement improved clay needs to be considered when the stress path for the actual field conditions differs from that in conventional laboratory testing. In addition to strength parameters, the modulus of deformation that is consistent with the actual encountered stress path is also needed for reasonable predictions.

A 3D numerical analysis of wave-induced seabed response around a monopile structure

ABSTRACT Despite the numerous ideas concept for an offshore wind turbine foundation, the monopile foundation is the most widely adopted concept in engineering practices. In this paper, a 3-dimensional integrated numerical model is established to study the wave-induced oscillatory seabed responses around a monopile foundation by adopting the Reynolds-Average Navier-Stokes (RANS) equation with turbulence closure model for the mean flow and the Biot’s consolidation equation for porous seabed as the governing equations respectively. The present wave and seabed sub-models in this studies are verified with physical experimental results and an analytical solution, while for the monopile structure, the wave impact force exerted on it are calculated and verified with physical experimental data to show that the present model has the ability to simulate the wave-seabed-pile structure interaction (WSSI-PILE). The numerical investigations on the monopile foundation indicated that the wave impact force on the pile structure and the seabed foundation has a very significant impact on horizontal displacement of the monopile within the seabed and the pile rocking motion. Parametric studies analysis on the effect of wave height, seabed permeability and pile structure diameter also indicated significant influence on the oscillatory wave-induced dynamic response .

Experimental and numerical analysis of a backpressure Banki inline turbine for pressure regulation and energy production

Water distribution networks have become, in recent years, a major opportunity for the harvesting of renewable energy, which is otherwise dissipated though hydrovalves installed for discharge and pressure regulation. Mini and micro hydroturbines have the capability of providing the same functionality of hydrovalves, producing at the same time a relevant amount of electric power. In this paper a 10 kW prototype of a new compact in-line turbine, named Power Recovery System (PRS), has been designed, constructed and tested in the hydraulic laboratory of the University of Palermo. The proposed device is a Banki-type micro-turbine, with positive outflow pressure and a mobile regulating flap for hydraulic control of the characteristic curve. The device is aimed to control pressure or discharge inside a water transport or distribution network, while producing energy with good efficiency values, up to 76%. Using two pressure meters located immediately before and after the turbine, it is possible to control the net head with given discharge (passive mode) or to control discharge by regulating the net head (active mode). 3D numerical analysis and laboratory measurements provide a low variation of efficiency for different positions of the mobile flap, especially for low variations in discharge.

2D numerical analysis of the influence of near-bank vegetation patches on the bed morphological adjustment

This paper investigates the influence of near-bank vegetation patches on the bed morphological adjustment in open channel flow systems. The 2D depth-averaged hydro-morphological model is adopted for this investigation, which is first validated by laboratory experimental data measured in an open channel with a single near-bank vegetation patch. The validated model is then applied for extensive numerical simulations, with the aim of conducting a systematic analysis of the influence of different geometric controlling parameters on the bed morphological evolution. The controlling parameters taken into account for numerical analysis include the angle of repose value (RAV) of sediment, vegetation density (VD), patch length (PL) and patch width (PW). The numerical results and analysis show that: (1) the RAV of sediment with slope-failure parametrization only influences the shape of the transverse bed topography in the junction region; (2) increase in VD, PL and PW that substantially enhances flow blockage effect encourages the growth of the pool adjacent to the patch in three dimensions; (3) increase in VD, PL and PW produces analogous retrogressive erosion (erosion toward the upstream) in the pool region, presumably due to the increase in flow resistance. Additional numerical experiments suggest that the staggered-order distribution of multiple patches might be an optimal choice for channel restoration and conservation since pools and riffles with larger scales can be produced.

Using 3D Numerical Analysis for the Assessment of Tunnel–Landslide Relationship: Bahce–Nurdag Tunnel (South of Turkey)

Owing to the increase in population, transportation has become one of the major research topics. Among existing transportation systems, railway is one of the most economic and fast systems, and therefore, there has been an increase in new railway constructions in recent years. In Turkey, the longest railway tunnels, the Bahce–Nurdag high-speed rail tunnels, are under construction in the southern part of the country. This twin tubes tunnels are approximately 10 km in length, and they are excavated using tunnel boring machines (TBM). The tunnel route locates in the East Anatolian Fault Zone and the portal region is composed of debris and old landslide deposits. For this reason, mitigating the potential landslide hazard is critical for the tunnel. Therefore, the present study investigates the TBM tunnelling–landslide relationship by employing 3D numerical analyses. The analyses show that the last 600 m of the tunnel has a potential landslide hazard and some additional measures should be considered along this part to ensure tunnel safety. The tunnel conditions are highly complex, and thus it is an interesting case for tunnel engineers.

Effect of segmental joint stiffness on tunnel lining internal forces under static conditions

According to the wide application of segmental lining in mechanized tunneling, recognizing the behavior of segmental lining joints is important in tunnels designing. In the structural analysis of the tunnel segmental lining, segmental joints can be considered as elastic joints, and their stiffness characteristics are affected by the rotational, shear, and axial stiffness. The purpose of this work is to investigate the effect of the rotational, shear, and axial stiffness of segmental lining joints on the internal forces (bending moment and axial force)under the static conditions. For this purpose, a 3D numerical analysis was carried out using the ABAQUS software. The results obtained show that by increasing the rotational stiffness of the segmental joint, the bending moment increases, and for lower values of rotational stiffness, the bending moment variations are higher, while the axial force variations are very slight in comparison with the bending moment. By increasing the axial and shear stiffness of the segmental joint, changes of the bending moment and axial force in segmental lining are negligible.

A numerical analysis of effect of segmental lining joints on tunnel support internal forces under seismic loading

During an earthquake, the better performance of segmental tunnel lining, compared to the continuous in-cast concrete lining, is generally related to the joints between segments. In order to better understand the influence of the segment joints, their effect on the internal forces induced in tunnel lining simultaneously with the effects of the other influential parameters should be considered. In this work, the segmental joints were simulated by the representative stiffnesses and effects of these characteristics in relation to the other parameters such as the soil-liner interface behavior, number of segments in each ring and thickness of segments on the internal forces induced in structure were investigated. For this purpose, 2D numerical analyses were performed and the results obtained were discussed. Results showed that under the seismic condition, the components that had the most significant role on the internal axial forces induced in the segmental lining were rotational stiffness and axial stiffness of joints. Also the bending moments were more affected by the rotational stiffness. Generally, the radial joint stiffness had a less effect on the induced internal forces. With increase in the number of segments and their thickness, the effect of joint stiffness on the internal forces increases and the design of joints should be given more attention; however, the effects of joint stiffness and frictional behavior at the soil-liner interface on the maximum induced forces are almost independent from each other. Also in a specified joint behavior, by variation in each one of the other parameters including the soil-liner interface condition, number of segments and their thickness, the absolute magnitude of the maximum induced internal forces sometimes change significantly.

Assessment of dynamic soil-structure interaction effects for tall buildings: A 3D numerical approach

Soil-structure interaction (SSI) phenomena are typically studied in the frequency-domain using the substructure approach, involving several simplifications. In this study, SSI effects for a 20-storey building are studied numerically performing time-domain 3D non-linear dynamic analyses, using an elastoplastic nonlinear constitutive model for the soil. Three foundation systems - a relatively shallow, a deeply embedded and a pile foundation - and two soil profiles are investigated and compared. Specifically, relative merits of site amplification, kinematic interaction and inertial interaction are isolated, and the role of foundation deformability and local stratigraphy is highlighted. To isolate such features, the results of the complete 3D models are compared with those provided by 3D numerical analyses of the sole building, of the foundation-soil systems and of the free-field soil deposit.Numerical results show that, for tall buildings, an increase in foundation deformability leads to a decrease of the maximum base shear force (seismic demand), to a higher rigid rotation of the foundation, but not to appreciably higher displacements of the structure. Moreover, possible situations where a (decoupled) substructure approach can lead to a misinterpretation of SSI phenomena are highlighted, as in the case of deep foundations crossing very soft soil layers.In addition, the use of embedded pile elements was proven to be an effective strategy in reducing the computational cost when performing complex 3D simulations of dynamic SSI problems.

Numerical simulation of solidification process in an ice-on-coil ice storage system with serpentine tubes

Energy consumption is rising around the world and most of the activities in the developed countries are dependent on electric energy. Thermal energy storages are one the ways to reduce energy consumption and balance the electrical power usage during the day. With thermal energy storages, or to be precise, with ice storage systems, energy usage peak can the shifted from the afternoon or early night to low-load hours of morning or midnights. In this study, a 3D unsteady numerical analysis was done in order to examine an ice storage system equipped with serpentine tube heat exchanger. The influence of two geometrical parameters, namely, tube diameter and serpentine tube row distance were investigated. The examined range for diameter and the serpentine tube row spacing were 15–21 and 30–100 mm, respectively. The results showed that placing the serpentine tube rows more distant to each other increases the ice formation so that the ice formation rate for the highest serpentine tube row distance compared to when the serpentine tube row distance is the lowest is higher by 24.68%. On the contrary, with a larger tube diameter, the rate of ice formation was decreased so that the smallest diameter had almost 5.9% more ice formation rate in comparison with the case with the largest tube diameter.

3D numerical flow analysis of the non-uniformity induced by a reshaped geometry of the symmetrical suction elbow

3D numerical flow analysis of the non-uniformity induced by a reshaped geometry of the symmetrical suction elbow

3D Numerical Limiting Case Analyses of Lateral Spreading in a Column-Supported Embankment

AbstractThis paper presents three-dimensional (3D) numerical analyses of a column-supported embankment case history using the finite-difference method. An undrained end-of-construction analysis is ...

Advanced Seismic Analyses of “Apennine Churches” Stroked by the Central Italy Earthquakes of 2016 by the Non-Smooth Contact Dynamics Method

The dynamic behaviour and the seismic vulnerability of different masonry “Apennine Churches”, dramatically damaged by the last shocks sequence of 2016 that occurred in Central Italy, have been studied in this paper by means of advanced 3D numerical analyses with the Discrete Element Method (DEM). Thus, a discontinuous approach has been used to assess the dynamic properties and the vulnerability of the masonry structure, through large deformations regulated by the Signorini’s law, concerning the impenetrability between the rigid bodies, and by the Coulomb’s law, regarding the dry-friction model. The major purpose of this study is to highlight that relevant data on the real structural behaviour of historical masonry can be provided through advanced numerical analyses. The comparison between the results of the numerical simulation and the survey of the existing crack pattern of the churches permitted to validate the used approach. Finally, from the results and conclusions of these cases study, it is possible to affirm that the used methodology can be applied to a wide variety of historical masonry structure in Europe.

Numerical study on thermal stress cutting of silicon wafers using two-line laser beams

We propose a method of cleaving silicon wafers using two-line laser beams. The base principle is separating the silicon wafer using crack propagation caused by laser-induced thermal stress. Specifically, this method uses two-line laser beams parallel to the cutting line such that the movements of the laser beam along the cutting line can be omitted, which is necessary when using a point beam. To demonstrate the proposed method, 3D numerical analysis of a heat transfer and thermo-elasticity model was performed. Crack propagation was evaluated by comparing the stress intensity factor (SIF) at the crack tip with the fracture toughness of silicon, where crack propagation is assumed begin when the SIF exceeds the fracture toughness. The influences of laser power, line beam width, and distance between two laser beams were also investigated. The simulation results showed that the proposed method is appropriate for cleaving silicon wafers without any thermal damage.