3D Numerical Model Research Articles

Serviceability of railway slab track foundations with retaining walls under train loading

ABSTRACT Railway retaining wall designs tend to disregard vehicle-induced trackbed deformation control, despite its potential impact on infrastructure serviceability. To fill this gap, this study seeks to develop an improved method to assess the performance of railway gravity retaining walls, specifically focusing on managing slab trackbed deformation. Utilizing a validated 3D numerical model, the research examines the impact of five parameters – wall width, location, inclination, embankment height, and ground-bearing capacity – on trackbed surface displacement (ω) arising from train loading. The multivariate adaptive regression splines (MARS) approach is applied to establish the mathematical relationship between these factors and an assessment indicator for evaluating track foundation serviceability. This indicator is the trackbed surface displacement index (R ω ), signifying the ratio of the maximum allowable to the practical ω value. Results highlight the necessity for comprehensive retaining wall design to ensure R ω ≥1.0, particularly when the wall is near the track, steeply inclined, or supporting a tall embankment.

Development of innovative groynes to establish fish passability of regulated rivers based on the example of the Wien River, Austria. Part I: Impact of groyne parameters on water depth and velocity

AbstractRivers in Europe have been heavily modified over the last 200 years, with a significant impact on their ecology and environment. This also applies to rivers like the Wien River, Austria, which are designed as overwide concrete channels for the benefit of flood protection. To achieve a good ecological potential in such heavily modified water bodies, one key element is fish passability. This requires an increase in the water level at low flow conditions and a reduction of the flow velocity. The aim of this study is to assess whether groynes are suitable for this application. A design study was conducted to examine the effect of individual groyne parameters on water depths and velocities. Physical experiments were carried out in a laboratory flume at a scale of 1:8. In addition, a 2D numerical model was used. It was found that the groynes had to be submerged and the alignment had to be repelling to achieve both requirements. The configuration of the groyne height, distance and degree of obstruction parameters were crucial. The groyne angle and shape had a minor effect and can be used for fine‐tuning. The best groyne design created a passable section for fish. Thereby, and through sedimentation, the best design contributed to an ecological improvement. However, it did not create habitats and did not constitute a fullfledged restoration. In general, submerged groynes can fulfil the hydraulic requirements for fish passage in heavily modified water bodies with a fixed bed.

Retentiveness of rare earth elements in garnet with implications for garnet Lu‐Hf chronology

AbstractIncorporation of rare earth elements (REE) in garnet enables garnet chronology (Sm‐Nd, Lu‐Hf), and imparts a garnet‐stable signature on cogenetic phases, which allows petrochronology and general petrogenetic tracing of garnet stability in minerals and melts. Constraints on the uptake and redistribution mechanisms, as well as on the diffusive behaviour of REE in garnet are required for allowing accurate interpretation of REE signatures and ages. Garnet REE profiles are often measured to gain insight into the nature and cause of REE zoning. Interpretation of such profiles is nevertheless complicated by poor constraints on the extent of diffusive relaxation. This is especially relevant for Lu, which, according to experiments, has a relatively high diffusivity and thus may re‐equilibrate with possible consequences for Lu‐Hf chronology. To provide new insight into the REE systematics of garnet, we applied quantitative trace‐element mapping of garnet grains from metamorphic rocks that record peak temperatures above 750°C and cooling rates as low as 1.5°C Ma−1. Garnet in all samples preserves Rayleigh‐type or oscillatory growth zoning with sharply defined interfacial angles that match the garnet habit. Re‐equilibration of REE compositions appears restricted to domains with nebulous and patchy zoning, which likely form by interface‐coupled dissolution and re‐precipitation reactions mediated by fluids or melts, rather than REE volume diffusion. The possible effect of Lu diffusion in the analysed grains was investigated by comparing the observations to the results from 2D numerical modelling using Lu diffusivities from recent diffusion experiments. This test indicates that Lu diffuses significantly slower in natural garnet than experiments predict. The retentiveness of REE in garnet demonstrates the reliability of REE signatures in magmatic tracing and petrochronology and establishes Lu‐Hf chronology as a robust means of dating garnet growth and recrystallization in metamorphic rocks, including those that underwent high‐ or ultrahigh‐temperature conditions.

Estimating maximum initial wave amplitude of subaerial landslide tsunamis: A three-dimensional modelling approach

Landslide tsunamis, responsible for thousands of deaths and significant damage in recent years, necessitate the allocation of sufficient time and resources for studying these extreme natural hazards. This study offers a step change in the field by conducting a large number of three-dimensional numerical experiments, validated by physical tests, to develop a predictive equation for the maximum initial amplitude of tsunamis generated by subaerial landslides. We first conducted a few 3D physical experiments in a wave basin which were then applied for the validation of a 3D numerical model based on the Flow3D-HYDRO package. Consequently, we delivered 100 simulations using the validated model by varying parameters such as landslide volume, water depth, slope angle and travel distance. This large database was subsequently employed to develop a predictive equation for the maximum initial tsunami amplitude. For the first time, we considered travel distance as an independent parameter for developing the predictive equation, which can significantly improve the predication accuracy. The predictive equation was tested for the case of the 2018 Anak Krakatau subaerial landslide tsunami and produced satisfactory results.

Three-Dimensional Simulations of Subaerial Landslide-Generated Waves: Comparing OpenFOAM and FLOW-3D HYDRO Models

AbstractThe recent destructive landslide tsunamis, such as the 2018 Anak Krakatau event, were fresh reminders for developing validated three-dimensional numerical tools to accurately model landslide tsunamis and to predict their hazards. In this study, we perform Three-dimensional physical modelling of waves generated by subaerial solid-block landslides, and use the data to validate two numerical models: the commercial software FLOW-3D HYDRO and the open-source OpenFOAM package. These models are key representatives of the primary types of modelling tools—commercial and open-source—utilized by scientists and engineers in the field. This research is among a few studies on 3D physical and numerical models for landslide-generated waves, and it is the first time that the aforementioned two models are systematically compared. We show that the two models accurately reproduce the physical experiments and give similar performances in modelling landslide-generated waves. However, they apply different approaches, mechanisms and calibrations to deliver the tasks. It is found that the results of the two models are deviated by approximately 10% from one another. This guide helps engineers and scientists implement, calibrate, and validate these models for landslide-generated waves. The validity of this research is confined to solid-block subaerial landslides and their impact in the near-field zone.

The Development of a 2D Numerical Model of a Device Using the Elastocaloric Effect to Cool Electronic Circuits

The scientific community has been working hard lately to develop fresh, environmentally friendly refrigeration technologies. Those based on solid-state refrigerants are among the Not-In-Kind Refrigeration Technologies that show great promises. The one based on the elastoCaloric Effect is among the most interesting of them. This paper presents the development of a 2D numerical model for a device harnessing the elastocaloric effect with the primary objective of cooling electronic circuits. The study focuses on the intricate interplay between mechanical and thermal aspects, capturing the dynamic behavior of the elastocaloric material in response to cyclic mechanical loading. The numerical model incorporates detailed descriptions of the electronic circuits, accounting for heat dissipation and thermal management. Through simulations, the optimal configuration for efficient cooling is explored, considering various operative conditions and mechanical loading conditions (tensile and bending). The findings contribute to the advancement of elastocaloric cooling technology, offering insights into the design and optimization of devices aimed at enhancing electronic circuit performance through effective thermal control. The results that the most promising configuration is based on bending, a design choice resulting appropriate for cooling the electronic circuits.

Effect of forced ventilation strategy on the thermal performance of finned-Trombe wall

Compared with the natural ventilation (NV) strategy, the forced ventilation (FV) strategy has inherent characteristics. However, the research on the effect of FV strategy on the thermal performance of finned-Trombe wall (F-TW) is still lacking so far. To fill this gap, in this study, a 3D numerical model that only takes into account heat loss through the glass cover was created to evaluate the impacts of ventilation strategy, inlet airflow speed, fin geometric factors and external environmental parameters on the thermal performance of F-TW. The main findings demonstrate that the thermal efficiency ηth and exergic efficiency ηex under FV strategy first grow and then decline as the inlet airflow speed uin increases, with the extreme value appearing at around 0.50 m/s of uin. The optimal ηth and ηex can reach 99.76% and 14.89% respectively when the relative fin height h* = 0.90 and relative fin spacing s* = 0.02. ηth and ηex exhibit a tendency of steady growth with increasing h* and decreasing s*. The h* has a stronger impact on the thermal performance than s*. The FV strategy can not only improve the F-TW's thermal performance by effectively changing the flow and temperature fields in the channel, but also alters the variation law between s* and thermal performance. The optimal ηth and ηex are both increased by 39.18%, compared with the NV strategy, and 13.49%, in comparison to the case without fins. Improving the solar radiation intensity, reducing the outdoor ambient wind speed and increasing the outdoor ambient temperature are beneficial to the F-TW's thermal performance. Aiming at F-TW, the significance of this study is to provide the basis for the performance assessment under the FV strategy, as well as the selection of different ventilation strategies.

Fluctuations in abundance of the striped venus clam Chamelea gallina in the southern Adriatic Sea (Central Mediterranean Sea): knowledge, gaps and insights for ecosystem-based fishery management

An assessment on the fluctuations in abundance of the striped venus clam (Chamelea gallina) in the southern Adriatic Sea (Central Mediterranean Sea), and the northern Gargano area, has been conducted through both historical information and recent data from monitoring surveys during the period 1997–2019. Production trends, conditions of the commercial stock biomass, and depth distribution pattern of juveniles and commercial sizes were analysed testing temporal differences. Moreover, the exploitation of the clam beds and recruitment events were investigated in 2018–2019. Changes in abundance were analysed using non-parametric tests for both juvenile (length class, LC < 22 mm) and commercial (LC ≥ 22 mm) fractions. Hydrodynamic changes, temperature and salinity variations were explored using a 3D hydrodynamic numerical model (MIKE 3 FM-HD) and statistical analysis, as well as changes in benthic assemblages impacted by hydraulic dredges were investigated through PERMANOVA and other multivariate analysis.The results showed a temporal decline of production and biomass of C. gallina during the 1997–2019 period, and a regression of the depth limit in the clams’ distribution towards shallower waters. A significant reduction in juveniles was observed during 2018–2019 with a very limited recruitment. The fishing exploitation showed high impacts on the commercial stock and benthic assemblages in the summer of 2018. Overall, water currents were predominantly directed offshore in 2018, during the C. gallina spawning period. This could affect the larval dispersal and settlement on unsuitable bottoms. Anomalies in temperature (high peaks in August 2018, > 28 °C) and salinity (low values in spring 2018, < 37 PSU) could have induced stress and mortality events on the entire clam bed in the study area. This first study highlights the need to integrate environmental information in the assessment of commercial stocks of clams in the Adriatic Sea, to better understand climate change effects on the fluctuations and to support effective ecosystem-based fishery management.

Inductive 3D numerical modelling of the tibia bone using MRI to examine von Mises stress and overall deformation

Abstract As the main load bearer throughout the gait cycle, the tibia is a crucial bone in the lower leg that distributes ground reaction forces with each stride. Comprehending the distribution of stress inside the tibia is essential for both avoiding fractures and developing efficient methods of redistributing load to promote healing and biomechanical correction. The study examined the stress, strain, and deformation encountered by the tibia over a 7-s walking cycle using an ANSYS workbench software, using tibia bone under a period of force applied to the boundary condition at intervals of 0.2 s. The tibia encounters stress levels varying from 0 to 1,400 N, exhibiting a regular pattern that aligns with the loading attributes often associated with traditional walking. The research conducted in this study identified the occurrence of maximum stress levels, measuring 25.45 MPa. Additionally, related peak elastic strains and deformations were observed, measuring 2.19 × 10−3 and 2.43 mm, respectively. The patterns that have been seen indicate that there is an initial contact of the foot with the ground, followed by the bearing of weight and subsequently the toe-off. These observed patterns closely resemble the natural motion of the foot during the act of walking. Temporal fluctuations in elastic strain through the tibia throughout a gait cycle reveal that the strain is mostly cantered at the medial surface of the tibia. Additional investigation into the elastic properties and overall deformations of the tibia yielded valuable observations on prospective areas of interest within the bone’s structure. These findings are of utmost importance for biomechanical assessments and the identification of potential injury hazards in subsequent research endeavours.

Automation of superconducting cavity cooldown process using two-layer surrogate model and model predictive control method

Superconducting cavity is the key equipment of the superconducting accelerator, which provides higher acceleration voltage and higher frequency power per unit length, and saves equipment space. Superconducting cavities need to be gradually cooled from ambient temperature (300 K) to the superconducting temperature (4.2 K or below) during the test and operation. The temperature difference on the cavity must be strictly limited during the cooldown process to prevent excessive thermal stress on the surface of the superconducting cavity. Since this cooldown process for the superconducting cavity is a typical large hysteresis, non-linear process that is difficult to control automatically using decoupled proportion integral derivative (PID) methods directly, a less efficient manual control scheme is normally adopted. In this paper, 3D numerical simulation, 1D pipe and 0D tank model with artificial neural network (ANN) were combined to generate a two-layer surrogate model that can balance computational accuracy and speed, to improve the automation and cooling efficiency of the superconducting cavity cooldown process. In order to achieve automatic control of the cooling procedure for the superconducting cavity, a model predictive control (MPC) approach was also built on the basis of this two-layer surrogate model. According to the results of the experiment test, the improved method could realize a quick and smooth cooldown process of the superconducting cavity, during which the temperature difference on the cavity could satisfy the requirements. Additionally, the improved automatic cooldown method was more adaptable and saved 29 % more time than the original manual control method. The foundation for a more intelligent automated control of future large cryogenic systems or other system with the large hysteresis, non-linear properties, was laid.

Hybrid response surface method for system reliability analysis of pile-reinforced slopes

To consider the complex soil-structure interaction in a pile-slope system, it is necessary to analyze the performance of pile-slope systems based on a three-dimensional (3D) numerical model. Reliability analysis of a pile-slope system based on 3D numerical modeling is very challenging because it is computationally expensive and the performance function of the pile failure mode is only defined in the safe domain of soil stability. In this paper, an efficient hybrid response surface method is suggested to study the system reliability of pile-reinforced slopes, where the support vector machine and the Kriging model are used to approximate performance functions of soil failure and pile failure, respectively. The versatility of the suggested method is illustrated in detail with an example. For the example examined in this paper, it is found that the pile failure can significantly contribute to system failure, and the reinforcement ratio can effectively reduce the probability of pile failure. There exists a critical reinforcement ratio beyond which the system failure probability is not sensitive to the reinforcement ratio. The pile spacing affects both the probabilities of soil failure and pile failure of the pile-reinforced slope. There exists an optimal location and an optimal length for the stabilizing piles.

3D Stresses and Velocities Caused by Continental Plateaus: Scaling Analysis and Numerical Calculations With Application to the Tibetan Plateau

AbstractUnderstanding stresses is crucial for geodynamics since they govern rock deformation and metamorphic reactions. However, the magnitudes and distribution of crustal stresses are still uncertain. Here, we use a 3D numerical model in spherical coordinates to investigate stresses and velocities that result from lateral crustal thickness variations around continental plateaus like those observed for the Tibetan plateau. We do not consider any far‐field deformation so that the plateau deforms by horizontal dilatation and vertical thinning. We assume viscous creep, a simplified plateau geometry, and simplified viscosity and density distributions to couple the numerical results with a scaling analysis. Specifically, we study the impact of the viscosity ratio between crust and lithospheric mantle, a rectangular plateau corner, a stress‐dependent power‐law flow law and Earth's double curvature on the crustal stress field and horizontal velocities. Two orders of magnitude variation in crustal and lithospheric mantle viscosities change the maximum crustal differential stress only by a factor of ≈2. We derive simple analytical estimates for the crustal deviatoric stress and horizontal velocity which agree to first order with 3D numerical calculations. We apply these estimates to calculate the average crustal viscosity in the eastern Tibetan plateau as ≈1022 Pa · s. Furthermore, our results show that a corner strongly affects the stress distribution, particularly the shear stresses, while Earth's curvature has a minor impact on the stresses. We further discuss potential implications of our results to strike‐slip faulting and fast exhumation around the Tibetan plateau's syntaxes.

Multifactor roadmap for designing low‐power‐consumed micro thermoelectric thermostats in a closed‐loop integrated 5G optical module

AbstractAs the core components of fifth‐generation (5G) communication technology, optical modules should be consistently miniaturized in size while improving their level of integration. This inevitably leads to a dramatic spike in power consumption and a consequent increase in heat flow density when operating in a confined space. To ensure a successful start‐up and operation of 5G optical modules, active cooling and precise temperature control via the Peltier effect in confined space is essential yet challenging. In this work, p‐type Bi0.5Sb1.5Te3 and n‐type Bi2Te2.7Se0.3 bulk thermoelectric (TE) materials are used, and a micro thermoelectric thermostat (micro‐TET) (device size, 2 × 9.3 × 1.1 mm3; leg size, 0.4 × 0.4 × 0.5 mm3; number of legs, 44) is successfully integrated into a 5G optical module with Quad Small Form Pluggable 28 interface. As a result, the internal temperature of this kind of optical module is always maintained at 45.7°C and the optical power is up to 7.4 dBm. Furthermore, a multifactor design roadmap is created based on a 3D numerical model using the ANSYS finite element method, taking into account the number of legs (N), leg width (W), leg length (L), filling atmosphere, electric contact resistance (Rec), thermal contact resistance (Rtc), ambient temperature (Ta), and the heat generated by the laser source (QL). It facilitates the integrated fabrication of micro‐TET, and shows the way to enhance packaging and performance under different operating conditions. According to the roadmap, the micro‐TET (2 × 9.3 × 1 mm3, W = 0.3 mm, L = 0.4 mm, N = 68 legs) is fabricated and consumes only 0.89 W in cooling mode (QL = 0.7 W, Ta = 80°C) and 0.36 W in heating mode (Ta = 0°C) to maintain the laser temperature of 50°C. This research will hopefully be applied to other microprocessors for precise temperature control and integrated manufacturing.

Numerical investigation on the exhaust gas combustion of an SOFC in a catalytic multichannel burner

The utilization of the exhaust gas of a solid oxide fuel cell is important to improve the energy efficiency and control pollutant emission. In this work, the combustion of solid oxide fuel cell exhaust gas (H2/CO) in a honeycomb ceramic catalytic burner is investigated numerically. A 2D numerical combustion model with 17 channels is built to analyze the influence of channel position on thermal performance and combustion characteristics. The high burnout of H2 and CO is obtained as 96.75% and 97.75%, respectively. The channels can be divided into three groups from the inside to the outside as follows: part 1, from the 9th channel to the 13th channel; part 2, from the 14th channel to the 16th channel; and part 3, the 17th channel. The channels in the same group presented the same results of flow, temperature, and combustion. Compared with the other channels, the outermost channel shows notable differences in depressing the temperature of the whole channel, moving the maximum temperature downstream, enlarging the temperature bias of the lower and upper walls, and enlarging the combustion zone. H2 and CO perform different combustion processes in the honeycomb ceramic catalytic burner. Compared with H2, the initial position of CO conversion is more affected by channel distribution. In the 17th channel, the CO oxidation rate is controlled mostly by the slower oxygen adsorption and the resulting low O(s) coverage. In the 9th channel, the CO oxidation rate is controlled mostly by the wall temperature and fuel-limited. The burnout rate of H2 changes from 95% to 99.9% with the channel position, but the burnout of CO varies little. The closer the channel to the outer wall, the higher the proportion of heterogeneous reaction and the more the generated heat. The generated heat by the channel can present a diversity of 4%.

Three-dimension holographic numerical simulation of gravity anomalies

In gravity-anomaly-based prospecting, it is difficult to achieve large-scale and high-precision inversion imaging of complex geological models. To address this issue, this paper proposes a three-dimensional holographic numerical simulation method for gravity anomalies. This method transforms the 3D partial differential equation of gravity potential into many independent 1D differential equations with different wavenumbers by performing a 2D Fourier transform along the horizontal direction. It decomposes a large-scale 3D numerical modeling problem into many 1D numerical modeling problems, which greatly reduces the computation and memory requirements of modeling, and each 1D differential equation is independent, so it has high parallelism. The vertical direction is reserved as the spatial domain, which has strict upper and lower boundary conditions; The horizontal 2D Fourier transform uses a holographic Fourier transform (Holo-FT) with a full interval of integration, consistent with the physical boundary in the horizontal direction, thus the physical information of the gravity potential described by the three-dimensional partial differential equation is fully and accurately simulated. Using the high parallelism of the algorithm, the CPU is used for parallel solving ordinary differential equations, while the GPU is used for parallel computing of Holo-FT, which implements the CPU-GPU parallel acceleration scheme and further improves the efficiency of this algorithm.

Fast segregation of thermal response functions in short-term for vertical ground heat exchangers

A detailed understanding of the short-term performance of the ground heat exchanger (GHE) is a major concern in the design of ground-source heat pumps (GSHP), as it has a significant impact in the efficiency and costs of the facility. The use of numerical models or artificial intelligence techniques may help in the short-term, although they are generally very time-consuming, becoming unpractical in numerous cases. The aim of this work is to obtain the thermal response factors according to the GHE, segregating the transient borehole behavior from the soil effect, based on a previous study which applies experimental data from thermal response tests (TRT) to the finite line source (FLS) model. The proposed method implies an extensive study of the fluid temperature as well as the development of new auxiliary thermal resistances related to the borehole and fluid, avoiding the implementation of numerical models. This procedure has been validated with the temperature outcomes of a 3D numerical model, obtaining low deviations, into a range of ±0.1 K, and mean absolute deviations below 0.01 K.

Rift Propagation Interacting With Pre‐Existing Microcontinental Blocks

AbstractRift propagation is a 3D thermo‐mechanical process that often precedes continental breakup. Pre‐existing microcontinental blocks and the associated lithospheric strength heterogeneities influence the style of rift propagation. Interestingly, some rifts propagate into pre‐existing blocks and eventually cut through them (e.g., the Zhongsha Block and the Reed Bank), while others bypass these microcontinental blocks forming distinct overlapping rift branches (e.g., the East African Rift System). In this study, we use 3D numerical models to investigate the interaction between microcontinental blocks and rift propagation under different far‐field extension rates. In doing so, we assess the impact of mantle lithospheric thicknesses and lower crustal rheology on the style of rift propagation. Our models reproduce the two types of rift propagation, characterized by propagating rifts that either split or bypass the pre‐existing microcontinental blocks. We find that lithospheric thickness exerts dominant control, while lower crustal rheology of microcontinental blocks and the extension rate have less effect on rift propagation. Our model results can explain rift propagation patterns, block rotation and strong lithospheric thinning in the South China Sea, the East African Rift System, and the Woodlark Basin.

3D numerical modeling of wave–monopile–seabed interaction in the presence of a scour hole

Coastal engineers are deeply concerned about wave-induced seabed instability around monopile foundations. Most prior studies have primarily focused on the seabed response around monopiles on flat seabeds, often neglecting the presence of scour holes commonly found in engineering practice. This study thoroughly investigates seabed response and liquefaction around monopiles of scour holes. The examination involves analyzing 3D flow velocities, dynamic wave loads, pore pressures, soil effective stresses, and wave forces around a monopile with a scoured profile. The analysis uses a model that integrates the interactions between waves, seabed, and structures, and it is implemented within the OpenFOAM framework. The study meticulously assesses the impact of scour holes on seabed responses and liquefaction zones around monopile foundations. Numerical results reveal that: (1) The magnitude of the pore pressure within the scoured seabed is reduced relative to a flat seabed; (2) Considering the scour hole effect leads to a more uniform distribution of liquefaction depth around the monopile; (3) This effect intensifies with a higher saturation degree, while it exhibits a pattern of increase, followed by a decrease with an increase in permeability.

Numerical Simulation Study on the Effect of Preinjected CO2 on the Hydraulic Fracturing Behavior of Shale Oil Reservoirs.

Due to the low permeability and apparent mechanical anisotropy of shale reservoirs, shale oil production highly depends on the performance of hydraulic fracturing of the tight reservoir. Pre-injection of CO2 before hydraulic fracturing treatment has been proven beneficial to enhance shale oil production. A comprehensive understanding of the effect of changes in the properties of shale reservoirs after preinjected CO2 on the hydraulic fracturing behavior of shale reservoirs is essential to improve the stimulated reservoir volume (SRV) of shale oil reservoirs. In this study, comprehensive evaluating parameters were proposed to specify the variation of mechanical properties of shale rock at different soaking times of CO2 based on published testing parameters of shale. Accordingly, a three-dimensional (3D) numerical model was established and three groups of horizontal well fracturing cases with different cluster spacings were conducted based on the adaptive FE-DE method to simulate and compare the hydraulic fracturing behavior in the reservoirs with different mechanical properties. We established a quantitative relationship between the alterations in reservoir properties and the stimulated reservoir volume. The results indicate that both the brittleness and conductivity properties of shale rock are dramatically improved as the increment of soaking time of CO2. It is beneficial to improve the SRV, and the initiation pressure is reduced with the increment of soaking time of CO2. However, as the stress shadow effect is involved in the horizontal well fracturing, the complexity of the hydrofracturing crack is significantly enhanced to restrain the development of hydrofracturing crack. When the cluster spacing is larger, the stress shadow effect is weakened, and the weakening effect of CO2 soaking on reservoir is more obvious.

Seismic collapse assessment of single-column bridge piers using the applied element method

Several single-column-bent bridges have collapsed in the past under earthquakes. Different factors associated with poor structural design and/or construction including inadequate and/or prematurely terminated longitudinal reinforcement (LR), insufficient concrete confinement, or insufficient transverse reinforcement (TR) were identified and reported. Different alternative designs or retrofitting solutions were also proposed and examined. One of the well-known samples of this bridge type was the elevated Hanshin Expressway Bridge (HEB), which collapsed in the 1995 Kobe earthquake. In that incident, 18 circular single-column piers (SCPs), monolithically connected to the deck, failed and collapsed. Here, the seismic progressive collapse behaviour of SCPs of the HEB was investigated using non-linear dynamic analyses of three-dimensional numerical models created by way of the applied element method (AEM). The results obtained agreed well with field observations after the earthquake. Two alternative design solutions for improving the seismic response of the original model were also considered and the efficiency of the solutions was assessed. Results showed that the AEM is capable of modelling the progressive collapse procedure for concrete bridges with sufficient accuracy. The results proved greater effects of the anchorage length of the LR as well as the space between the TR in the collapse behaviour of the pier.