bluuebunny/crossref_metadata_2025 huggingface dataset:
Probing the influence of cation distribution on the vibrational dynamics and phase transitions in Mg-doped zinc ferrites: Quantum mechanical study
Authors: Almutairi Tahani Saad
Published: May 2024

The assignment of vibrational modes in spinel ferrites using infrared (IR) and Raman spectroscopy is a task of considerable complexity due to the intricate vibrational behavior exhibited by these materials. This complexity is further compounded by the presence of a variety of metal cations occupying distinct positions in the crystal lattice. In the present study, we have undertaken a detailed analysis of the vibrational spectrum of Mg–Zn ferrite utilizing an ab initio periodic quantum-mechanical approach. We employed a localized Gaussian-type function basis set in conjunction with the B3LYP hybrid Hamiltonian to achieve this. The obtained results indicate that the ground state of Mg–Zn ferrite is an open-shell system with a mixed structure, characterized by magnesium atoms predominantly occupying octahedral sites, zinc atoms at the tetrahedral site, and iron atoms distributed across both sites. We report a discernible free energy difference of 0.07 eV, which includes zero-point energy, corresponding to 812 K, between the antiferromagnetic ground state and a ferromagnetic arrangement within the normal structure. The variations in IR and Raman frequencies identified in this research, as compared to the existing literature, hold significant potential for determining the phase of Mg–Zn ferrites in experimental spectra. This advancement offers a vital step toward a deeper understanding of the vibrational properties and potential applications of these ferrites.
Phase diagrams and polarization reversal in nanosized HfxZr1−xO2−y
Authors: Eliseev Eugene A. , Zagorodniy Yuri O. , Pavlikov Victor N. , Leshchenko Oksana V. , Shevliakova Hanna V. , Karpets Miroslav V. , Yaremkevych Andrei D. , Fesenko Olena M. , Kalinin Sergei V. , Morozovska Anna N.
Published: May 2024

To describe the polar properties of nanosized HfxZr1−xO2−y, we evolve the “effective” Landau–Ginzburg–Devonshire (LGD) model based on the parametrization of the Landau expansion coefficients for polar and antipolar orderings. We have shown that the effective LGD model can predict the influence of screening conditions and size effects on phase diagrams, polarization reversal, and structural properties of nanosized HfxZr1−xO2−y of various shapes and sizes. To verify the model, we use the available experimental results for HfxZr1−xO2 thin films and oxygen-deficient HfO2−y nanoparticles prepared under different annealing conditions. X-ray diffraction, which was used to determine the phase composition of the HfO2−y nanoparticles, revealed the formation of a ferroelectric orthorhombic phase in them. Micro-Raman spectroscopy was used to explore the correlation of lattice dynamics and structural changes that depend on the oxygen vacancy concentration in the HfO2−y nanoparticles. Since our approach allows us to determine the conditions (shape, sizes, Zr content, and/or oxygen vacancy amount) for which nanosized HfxZr1−xO2−y are ferroelectric or antiferroelectric, we hope that the obtained results are useful for creation of next generation Si-compatible ferroelectric gate oxide nanomaterials.
Slow-motion spectroscopy paves the way for a nuclear clock
Authors: Miller Johanna L.
Published: May 2024

For the first time, the energy level of an atomic nucleus has been directly manipulated with a laser.
Are environmental water requirements being met in the Murray–Darling Basin, Australia?
Authors: Sheldon Fran , Rocheta Eytan , Steinfeld Celine , Colloff Matthew J. , Moggridge Brad , Carmody Emma , Hillman Terry , Kingsford Richard T. , Pittock Jamie
Published: May 2024

Context In implementing the Murray–Darling Basin Plan, jurisdictions have defined environmental water requirements (EWRs) for sites along Basin rivers. EWRs are the flows (frequency, magnitude, duration, and timing) required to achieve environmental outcomes; they are derived from flow-ecology relationships by using best available scientific knowledge. Aims To assess EWR achievement across the Murray–Darling Basin over a 43.5-year period (1 July 1979 – 31 December 2022) that included periods of drought as well as widespread flooding. Methods By using a published EWR assessment tool, we analysed the achievement of EWRs for small fresh, large fresh, bankfull and overbank flows for 23 sites. Key results At 65% of stream gauge sites assessed, most EWRs evaluated had not been met. We also compared analyses of different time periods, namely, a 43.5-year period, and a 10-year period since the Basin Plan was legislated. This highlighted some improvement in EWR achievement for the small fresh EWR. Conclusions and implications Despite some improvements, the continued lack of achievement in meeting EWRs is likely to be a major contributing factor to the ongoing poor health of channel, wetland (including Ramsar wetlands) and floodplain ecosystems across most of the rivers of the Murray–Darling Basin.
Structure and mechanism of the human CTDNEP1–NEP1R1 membrane protein phosphatase complex necessary to maintain ER membrane morphology
Authors: Gao Shujuan , Carrasquillo Rodríguez Jake W. , Bahmanyar Shirin , Airola Michael V.
Published: May 2024

C-terminal Domain Nuclear Envelope Phosphatase 1 (CTDNEP1) is a noncanonical protein serine/threonine phosphatase that has a conserved role in regulating ER membrane biogenesis. Inactivating mutations in CTDNEP1 correlate with the development of medulloblastoma, an aggressive childhood cancer. The transmembrane protein Nuclear Envelope Phosphatase 1 Regulatory Subunit 1 (NEP1R1) binds CTDNEP1, but the molecular details by which NEP1R1 regulates CTDNEP1 function are unclear. Here, we find that knockdown of NEP1R1 generates identical phenotypes to reported loss of CTDNEP1 in mammalian cells, establishing CTDNEP1–NEP1R1 as an evolutionarily conserved membrane protein phosphatase complex that restricts ER expansion. Mechanistically, NEP1R1 acts as an activating regulatory subunit that directly binds and increases the phosphatase activity of CTDNEP1. By defining a minimal NEP1R1 domain sufficient to activate CTDNEP1, we determine high-resolution crystal structures of the CTDNEP1–NEP1R1 complex bound to a peptide sequence acting as a pseudosubstrate. Structurally, NEP1R1 engages CTDNEP1 at a site distant from the active site to stabilize and allosterically activate CTDNEP1. Substrate recognition is facilitated by a conserved Arg residue in CTDNEP1 that binds and orients the substrate peptide in the active site. Together, this reveals mechanisms for how NEP1R1 regulates CTDNEP1 and explains how cancer-associated mutations inactivate CTDNEP1.
Brittle and ductile yielding in soft materials
Authors: Kamani Krutarth M. , Rogers Simon A.
Published: May 2024

Many soft materials yield under mechanical loading, but how this transition from solid-like behavior to liquid-like behavior occurs can vary significantly. Understanding the physics of yielding is of great interest for the behavior of biological, environmental, and industrial materials, including those used as inks in additive manufacturing and muds and soils. For some materials, the yielding transition is gradual, while others yield abruptly. We refer to these behaviors as being ductile and brittle. The key rheological signatures of brittle yielding include a stress overshoot in steady-shear-startup tests and a steep increase in the loss modulus during oscillatory amplitude sweeps. In this work, we show how this spectrum of yielding behaviors may be accounted for in a continuum model for yield stress materials by introducing a parameter we call the brittility factor. Physically, an increased brittility decreases the contribution of recoverable deformation to plastic deformation, which impacts the rate at which yielding occurs. The model predictions are successfully compared to results of different rheological protocols from a number of real yield stress fluids with different microstructures, indicating the general applicability of the phenomenon of brittility. Our study shows that the brittility of soft materials plays a critical role in determining the rate of the yielding transition and provides a simple tool for understanding its effects under various loading conditions.
A stable and robust fault diagnosis method for bearing using lightweight batch normalization-free residual network
Authors: Zhu Bao , He Chunmeng
Published: May 2024

The conventional deep learning-based bearing fault diagnosis methods tend to utilize denoising modules to improve the fault diagnosis performance in noisy scenes. However, the addition of denoising modules will increase expensive computational costs, leading to a delayed acquisition of fault diagnosis results. This work proposed a lightweight batch normalization (BN)-free residual network without any denoising modules for bearing fault diagnosis which properly rescaled the weights in a standard initialization instead of BN to avoid the exploding gradient problem and vanishing gradient problem at the beginning of training for deep neural networks. Therefore, it prevents the undesirable properties caused by BN. Compared with other methods, the fault diagnosis performance of the proposed method can maintain a high level with different input sizes and batch sizes. Especially in noisy scenes, the testing accuracy of fault diagnosis on different bearing datasets can be improved by 13.54% and 7.74% using fewer parameters and floating point operations on different bearing datasets.
In-beam PET monitoring of proton therapy: a method for filtering prompt radiation events
Authors: Ma Qiuhui , Yang Zhiyong , Mu Dengyun , Gao Min , Zhang Ruilin , Wan Lin , Qiu Ao , Xie Qingguo
Published: May 2024

Objective. In-beam positron emission tomography (PET) is a promising technology for real-time monitoring of proton therapy. Random coincidences between prompt radiation events and positron annihilation photon pairs can deteriorate imaging quality during beam-on operation. This study aimed to improve the PET image quality by filtering out the prompt radiation events. Approach. We investigated a prompt radiation event filtering method based on the accelerator radio frequency phase and assessed its performance using various prompt gamma energy thresholds. An in-beam PET prototype was used to acquire the data when the 70 MeV proton beam irradiated a water phantom and a mouse. The signal-to-background ratio (SBR) indicator was utilized to evaluate the quality of the PET reconstruction image. Main results. The selection of the prompt gamma energy threshold will affect the quality of the reconstructed image. Using the optimal energy threshold of 580 keV can obtain a SBR of 1.6 times for the water phantom radiation experiment and 2.0 times for the mouse radiation experiment compared to those without background removal, respectively. Significance. Our results show that using this optimal threshold can reduce the prompt radiation events, enhancing the SBR of the reconstructed image. This advancement contributes to more accurate real-time range verification in subsequent steps.
Impact of reduced differential transform under heat-moisture coupling on the hygrothermoelastic properties in cartesian coordinates
Authors: Sutar Chandrashekhar S , Patil Sandip N , Chaudhari Kamini K
Published: May 2024

The objective of this work is to analyze the effects of combined temperature and moisture in a rectangular plate under hygrothermal loading using hygrothermoelastic model. The reduced differential transform method is used to obtain the solution of temperature, moisture and stress. We have demonstrated the efficacy of the reduced differential transform approach to examine several aspects of the Hygrothermoelastic model. The results are illustrated numerically and graphically for porous composite material. From the study, it is observed that temperature shows a negative effect while moisture increases in a positive direction along spatial direction under the assumed initial and boundary conditions. The stresses are affected due to hygrothermal loading.
EfficientSkinSegNet: a lightweight convolutional neural network for accurate skin lesion segmentation
Authors: Deng Shuangcheng , Li Zhiwu , Zhang Jinlong , Hua Junfei , Li Gang , Yang Yang , Li Aijing , Wang Junyang , Song Yuting
Published: May 2024

Accurate segmentation of skin lesions is crucial for the early detection and treatment of skin cancer. In this study, we propose EfficientSkinSegNet, a novel lightweight convolutional neural network architecture specifically designed for precise skin lesion segmentation. EfficientSkinSegNet incorporates efficient feature extraction encoders and decoders, leveraging multi-head convolutional attention and spatial channel attention mechanisms to extract and enhance informative features while eliminating redundant ones. Furthermore, a multi-scale feature fusion module is introduced in the skip connections to facilitate effective fusion of features at different scales. Experimental evaluations on benchmark datasets demonstrate that EfficientSkinSegNet outperforms state-of-the-art methods in terms of segmentation accuracy while maintaining a compact model size. The proposed network shows promise for practical clinical diagnostic applications, providing a balance between segmentation performance and computational efficiency. Future research will focus on evaluating EfficientSkinSegNet’s performance on diverse semantic segmentation tasks and optimizing it for medical image analysis.
A multiple directions turning vehicle counting method at intersections based on arbitrary-oriented detection and stack Long Short-Term Memory
Authors: Li Shuang , Liu Chunsheng
Published: May 2024

The traffic flow parameters of turning vehicles at urban road intersections play an important role in the intelligent traffic system. Traffic road monitoring is difficult to cover large intersection scenes. With the application of unmanned aerial vehicles in traffic, drone-based intersection monitoring has great potential due to the large perspective. But there is rarely research on multiple turning vehicle counting at intersections based on drones. A few existing multiple turning vehicle counting methods are based on vehicle detection and tracking methods. However, the vehicles at the intersection have various orientations, the accurate information of the vehicle cannot be obtained by detection, and the tracking process is complicated and redundant for the counting task. Based on the traffic video at intersections taken by unmanned aerial vehicles, we propose a eight turnings vehicle counting model without complex tracking. Firstly, a spatial attention and channel adaptive attention model net is proposed for arbitrary-oriented vehicle detection to get the orientation and position of vehicles. Secondly, a turning spatio-temporal counting feature for different turning vehicles and its extraction method are proposed. Finally, the stack Long Short-Term Memory net based counting model is designed to process the turning spatio-temporal counting feature and counting eight different turnings vehicles at intersection. The experiments show that the proposed method can realize counting eight different turnings vehicles simultaneously in drone-based traffic video at the intersection without relying on complex multi-target tracking. The average counting accuracy has reached 98.18%.
Analytical modeling of nucleation and growth of graphene layers on CNT array and its application in field emission of electrons
Authors: Sharma Shruti , Sharma Suresh C
Published: May 2024

Carbon Nanotube (CNT) arrays and graphene have undergone several investigations to achieve efficient field emission (FE) owing to CNT’s remarkable large aspect ratio and graphene’s exceptional FE stability. However, when dense CNT arrays and planar graphene layers were used as field emitters, their field enhancement factor reduced dramatically. Therefore, in this paper, we numerically analyze the growth of a dense CNT array with planar graphene layers (PGLs) on top, resulting in a CNT-PGL hybrid and the associated field enhancement factor. The growth of the CNT array is investigated using Plasma Enhanced Chemical Vapor Deposition (PECVD) chamber in C2H2/NH3 environment with variable C2H2 flow, Ni catalyst film thickness, and substrate temperature followed by PGL precipitation on its top at an optimized cooling rate and Ni film thickness. The analytical model developed accounts for the number density of ions and neutrals, various surface elementary processes on catalyst film, CNT array growth, and PGLs precipitation. According to our investigation, the average growth rate of CNTs increases and then decreases with increasing C2H2 flow rate and catalyst film thickness. CNTs grow at a faster rate when the substrate temperature increases. Furthermore, as the chamber temperature is lowered from 750 °C to 250 °C in N2 environment and Ni film thickness grows, the number of the graphene layers increases. The field enhancement factors for the CNT array and hybrid are then calculated based on the optimal parameter values. The average height of the nanotubes, their spacing from one another, and the penetration of the electric field due to graphene coverage are considered while computing the field enhancement factor. It has been found that adding planar graphene layers to densely packed CNTs can raise its field enhancement factor. The results obtained match the current experimental observations quite well.
Effect of MWCNTs surface functionalization on the characterization of PVA/MWCNTs nanocomposites
Authors: Le Thi Mai Hoa , Vo Nguyen Da Huyen , Dang Dung My Thi , Doan Tin Chanh Duc
Published: May 2024

The present study aims to put forward the role of surface functionalization of multi-walled carbon nanotubes (MWCNTs) on the enhancement thermal and hydrophilicity properties of new nanocomposite based poly(vinyl alcohol)/surface functionalized MWCNTs (PVA/MWCNTs), prepared by a facile phase inversion process. In this study, the fabrication of PVA/MWCNTs nanocomposites is carried out using functionalized MWCNTs (f-MWCNTs) with different functional groups (–OH, –COOH, –NH2). The structural, morphological, thermal, hydrophilicity and physico-chemical properties of PVA/MWCNTs nanocomposites are characterized by XRD, FE-SEM, FT-IR, TGA and contact angle measurement. The FT-IR results confirm the formation of a hydrogen bond between MWCNTs and PVA chain. XRD analysis indicates an improvement in the crystallinity of the PVA/MWCNTs nanocomposite. TGA results reveal that the PVA/f-MWCNTs nanocomposites show higher thermal stability than pure PVA. It is revealed that PVA/MWCNTs nanocomposites based functionalized MWCNTs remarkably increase the degradation temperature, and thus enhancing the thermal properties. The highest weight loss (30.7 wt%) and degradation temperature (520 °C) values are obtained with PVA/f-MWCNTs(0.5 wt%). The contact angle measurement confirms that the hydrophobic properties of pure PVA became hydrophilic because of the functional groups of MWCNTs. The hydrophilicity of PVA/MWCNTs nanocomposites is increased with the increase in wt% of MWCNTs embedded in the nanocomposite.
Development of beamline control system for Hefei Advanced Light Facility
Authors: Liu Qun , Chen Liuguo , Liu Gongfa , Wang Xiao , Li Fang , He Bo
Published: May 2024

The design and the control scheme of beamline control system
for Hefei Advanced Light Facility (HALF;Hefei, People's Republic of
China) which is under construction is described in this paper.It
mainly includes, equipment protection safety, personal protection
safety,fast signal interlock and status monitoring and fault
diagnosis system. In this control system ,the human presence
perception function has been added to the personal protection safety
system. Multi-parameter status monitoring of key equipment on
beamline station can automatically alarm equipment failures and send
relevant personnel timely notifications. At the same time, it can
also provide early warning on the health status of key equipment on
the beamline. The system not only improves the safety and
reliability of beamline control, but also increases the degree of
automation and intelligence, reduces the workload of operation and
maintenance personnel, and improves operation and maintenance
efficiency.
Geometry of spinors: doubly-chiral plane-wave expansion
Authors: Fabbri Luca
Published: May 2024

We employ the polar re-formulation of spinor fields to see in a new light their classification into regular and singular spinors, these last also called flag-dipoles, further splitting into the sub-classes of dipoles and flagpoles: in particular, we will study the conditions under which flagpoles may be solutions of the Dirac field equations. We argue for an enlargement of the plane-wave expansion.
Investigation of JGS frost susceptibility testing method
Authors: Zheng Gong , Jin Hyunwoo , Ryu Byung Hyun , Lee Jangguen
Published: May 2024

Frost heave is a type of frost action that occurs when the soil temperature is below freezing temperature. Construction in cold regions is challenging and can cause severe damage to structures due to frost heave. The segregation potential (SP) is widely accepted in engineering design and for frost heave predictions as an indicator for frost susceptibility classification. The purpose of this study is to investigate the frost heave experiments in the JGS method and to evaluate the JGS frost susceptibility testing results for different soil mixtures with different SP through numerical simulation with a Thermal-Hydraulic coupled model. The results show good agreement between numerical simulation and test results for different degrees of frostsusceptible soils. This model is expected to provide accurate predictions of the frost heave behavior of different soils.
Evaluating wave force and interface fluid velocity distribution at the vicinity of a breakwater by considering consolidation of porous media
Authors: Zou S , Shi Z , Huang M
Published: May 2024

Previous studies have successfully simulated the interaction between wave and porous media using volume-averaged Reynolds-averaged Navier-Stokes (VARANS) equations. However, the consolidation of porous media subject to wave loading affects the progressing wave, which is crucial to computation of wave force and wave-porous media interface fluid velocity. Research on this aspect is scarce. This study adopted the
u
-p approximation for Biot dynamic consolidation theory to quantify the consolidation of porous media. The continuity condition on the interfaces between the wave and porous seabed was considered to achieve their interaction. Coupling algorithms of wave and porous seabed were validated against experimental measurements in the literature. An engineering case of wave traveling over a breakwater was examined, and computation results of wave pressures and interface fluid velocities at the vicinity of a breakwater by VARANS equations and wave-porous seabed coupling algorithm of this study were compared to explore the influence of the consolidation effect on the progressing wave.
3D SPH implementation to large deformation of granular mass using an advanced hypoplastic constitutive model
Authors: Zhu Chengwei , Wu Wei , Wang Shun , Peng Chong
Published: May 2024

In this study, an advanced hypoplastic model incorporating the critical state is integrated into smoothed particle hydrodynamics (SPH) for the numerical investigation of geotechnical large-deformation problems. Moreover, a return mapping strategy is proposed to regulate the stress state to avoid calculation failure. Furthermore, a closed-form solution to predicting the failure surface implicitly incorporated in the hypoplastic model is derived. The proposed SPH method is examined with element tests such as the oedometer test and biaxial compression test to observe a good performance of the SPH model. Finally, the SPH model is applied to numerically reproducing sand column collapse to investigate the effect of the initial void ratio on the behavior of soil.
Constitutive modeling of anisotropic small-strain stiffness behavior of Shanghai soft clay
Authors: Chen Zhengyi , Gu Xiaoqiang , Shi Zhenhao , Yang Min
Published: May 2024

Small strain stiffness plays an important role in determining the deformation of geotechnical engineering in soft soils. To model the anisotropic small strain stiffness behavior of soft clay, an enhancement to the bounding surface plasticity model is proposed. This enhancement involves incorporating the anisotropy in soil stiffness at very small strains and its non-linear degradation. Small strains are considered via cross-anisotropy elasticity, while the concept of intergranular strain is used to reflect the non-linear degradation of stiffness with strains and the effect of recent stress history. Using the proposed model, the triaxial test results on K0 consolidated Shanghai clay specimens are simulated to investigate the model’s performance. In the simulation, three typical shear stress paths are adopted. The comparison of the model simulations against experimental evidence is discussed, where the effects of anisotropy in initial soil stiffness and stress-induced anisotropy on the variation of small-strain stiffness, pore pressure, and shear-volume coupling response are highlighted.
Integrated database of granular soils under triaxial shear and its application in the prediction of stress–strain relationship
Authors: Xiong W , Wang J , Cheng Z
Published: May 2024

This study presents a novel data generation framework that generates a large database for machine learning (ML)-based soil model predictions. The dataset comprised 216 sets of triaxial tests on morphologically mutated and gene-decayed granular samples. This database was then estimated using five widely utilized ML algorithms to predict the stress-strain relationship of granular soils. They include the support vector machine (SVM), bagged trees, Gaussian process regression (GPR), and back propagation neural network (BPNN) algorithms. Following the hyperparameter settlement, model training, and testing, all the trained models captured the effects of the multiscale particle morphology, initial packing state, and confining stress. The excellent training and testing performances indicate the superior quality of the generated dataset. The fine tree, exponential GPR, and BPNN outperformed the Gaussian SVM and bagged trees in terms of the predictive performance. Among them, the exponential GPR exhibits the best model performance in reflecting the particle morphology effect, whereas the fine tree and BPNN generally exhibit good predictive performance for missing local information. Furthermore, all the models are tested by the micro-tomography (μCT) experimental data. The findings of this study were validated through a comparison between the DEM and model prediction results.
The impact of initial fabric anisotropy on cyclic liquefaction behavior with polygonal particles using the discrete element method (DEM)
Authors: Ajamnorouzi M , Hosseininia E S
Published: May 2024

Liquefaction is one of the most significant phenomena that can occur in soil during an earthquake. The destructive effects of this phenomenon on earth structures have captured the attention of many geotechnical engineers. Additionally, the gradual increase in pore water pressure during the cyclic loading induced by the propagation of earthquake waves, known as cyclic liquefaction, is a crucial factor that might lead to the complete loss of shear strength in soils. A better understanding of cyclic liquefaction is essential for improving earthquake hazard analysis and mitigating structural damage. Factors influencing liquefaction behavior include particle size, particle grading, and soil fabric. By “soil fabric,” we refer to the arrangement and positioning of particles with each other, particle shape, and the shape of voids among particles. This research aims to focus on the effects of fabric anisotropy on cyclic liquefaction of granular soils with angular particles. To carry out this investigation, the discrete element method has been employed. In the discrete element method, the geometry of particles and, generally, the soil fabric can be considered. In this research, specimens with varying particle orientation angles were produced and subjected to cyclic loading tests under undrained conditions. By examining the stress paths of specimens during cyclic loading, it is observed that the initial fabric and inherent anisotropy significantly influence the behavior of the specimens. Inherent anisotropy leads to varying numbers of cycles required for the initial liquefaction of each specimen. Furthermore, it is observed that as the particle orientation angle increases, the localization of axial strains shifts from tensile to compressive directions. The effect of inherent anisotropy plays a substantial role in the initial liquefaction (ru = 1). If the liquefaction of specimens is of interest at lower values of ru, the effect of inherent anisotropy can be disregarded.
Small-strain characterization of Shanghai clays by triaxial compression tests
Authors: Lan L , Ye G , Zhu W , Zhang Q
Published: May 2024

The mechanical properties of the upper Shanghai Layers 2-6 clays at small strain levels have been extensively investigated. Nonetheless, limited data exist on their small-strain characteristics through K
0-consolidated undrained triaxial compression tests, with even less information available for the deeper layers 8 and 10. This study employed a series of K
0-consolidated undrained TC tests on intact samples from both the upper layers 2-6 and the deeper layers 8 and 10 of Shanghai clay. We evaluated the undrained maximum secant stiffness (Eu

max) and reference shear strain (γ0.7
). An increase in over-consolidation ratio (OCR) results in a higher E
u
max/p’ and a more rapid decay of the G/G
max with the increasing shear strain (γ). As the value of γ
0.7 increases with I
p and decreases with OCR, a correlation between γ
0.7 and Ip
can be established. This study observed significant correlations between the E
u
max, effective stress (p’), and the maximum deviatoric stress, as well as between E
u
max and the cone resistance obtained from field cone penetration tests. These correlations offer methods to estimate E
u
max and γ0.7 values based on parameters that are more readily measurable, which provide critical references for the calculations and design parameters in foundation engineering within the Shanghai region.
Effect of geotechnical soil properties on CBR value: A review
Authors: Pule B B , Yendaw J A
Published: May 2024

This review paper presents the current research state of the relationship between geotechnical soil properties and the California bearing ratio (CBR) value. Geotechnical considerations are pivotal in civil engineering projects to prevent collapse and settlement failures, underscoring the importance of understanding detailed soil properties. A CBR test used for assessing stiffness modulus and shear strength guides the overlaying layer-thickness calculation during pavement design. Although expensive and complex, researchers have explored correlations and machine-learning algorithms for CBR prediction from soil properties. This study delves into the varying influence of properties such as compaction (optimum moisture content and maximum dry density) and index (liquid, plastic, and shrinkage limits) properties. The relevance of such properties to CBR is explored, examining their significance and potential interactions. This review highlights the multi-faceted effects of soil properties on CBRvalue, enabling informed pavement engineering decisions.
Novel apparatus for visualizing hydraulic fracturing in soils
Authors: Li Kun-peng , Chen Yong-gui
Published: May 2024

This paper presents a new apparatus designed specifically for visualizing hydraulic fracturing in soils. The apparatus comprises four main units: an injection cell, a visualization unit, a pressure/volume control unit, and a data acquisition unit. The injection cell is characterized by a transparent, high-transmittance polymethyl methacrylate top cover that enables direct visual observation. The visualization unit includes a visual studio and a high-resolution camera that captures macro-fracturing dynamics. The pressure/volume control unit enables specific test requirements to be satisfied during injection tests. The data acquisition unit records injection pressure and water volume data over time. To validate the performance of the novel apparatus, we conducted a systematic injection test on Gaomiaozi bentonite with a dry density of 1.3 g/cm3 and a water content of 9.39%. The results indicate that the apparatus accurately captures macro-fracturing dynamics and records injection pressure and water volume data in real-time.
Implementation of modified cam–clay model using closest point projection method under Cartesian coordinate system
Authors: Xie Zhongkai , Ren Gang , Xu Chao , Huang Zhiqiang
Published: May 2024

The modified Cam–Clay model is an elastoplastic soil model that holds a prominent position in civil engineering for its precise depiction of varied soil behaviors. Despite extensive examination of its numerical processes, the predominant focus on stress integration algorithms within the triaxial stress space presents challenges for individuals less acquainted with geotechnical science. In response to this, the present study derived the stress integration equations for the modified Cam–Clay model within the Cartesian coordinate system employing the closest point projection method. Subsequently, a finite element program was developed incorporating the derived integration process. This study computed and compared the consolidation processes under both drained and undrained conditions for cubic soil samples with various over-consolidation ratios using the developed program, ABAQUS, and analytical formulas. The findings demonstrate that equations integrated within the Cartesian coordinate system offer ease of understanding and programming. The feasibility, accuracy, and stability of the closest point projection method have been validated. Comparative analysis of soil samples across various over-consolidation ratios indicated a reduction in failure stress with an increase in over-consolidation ratio, indicating a higher propensity for failure under undrained conditions than under the drained conditions.
Coupled peridynamic modeling of hydraulic fracturing in rocks
Authors: Yang Changyi , Zhu Fan , Zhao Jidong
Published: May 2024

This paper presents a fully coupled peridynamics method for simulating hydraulic fracturing in rocks. The proposed method involves a rigorous coupling between the classical total-Lagrangian formulation and a new semi-Lagrangian formulation within the framework of peridynamics. The total-Lagrangian formulation is employed to simulate a rock subjected to fluid-driven fracturing, whereas the semi-Lagrangian formulation is used to solve the Navier–Stokes equations for fluids in a nonlocal manner. A coupling algorithm is developed between the two formulations to model fluid–solid interactions without causing unphysical penetration. The proposed method was validated through a simulation of a water column collapse problem. It was further validated using a Kristianovich–Geertsma–De Klerk (KGD) fracturing problem, where a plane strain fracture propagates owing to fluid injection. The proposed method reasonably captures the fracturing pattern, fracture propagation speed, and injection pressure better than the analytical solution. It offers a unified framework within the peridynamics theory for modeling solid, fluid, and fluid-driven fractures.
Anisotropic Breakage Mechanics for cemented granular materials
Authors: Shen Xianda , Buscarnera Giuseppe , Zhang Fengshou
Published: May 2024

The anisotropy of granular geomaterials is sensitive to their fabric, which exhibits anisotropic mechanical properties as a function of deposition history, microscopic fabric, and loading paths. Here, a new fabric-enriched continuum breakage model is proposed to examine the relation between elastic and inelastic anisotropy in granular materials and cemented granular materials. A microstructure model is first implemented in the framework of fabric-enriched continuum breakage mechanics (F-CBM), where the anisotropic behaviour prior to yielding is introduced through a symmetric second-order fabric tensor embedded in the expression of the elastic energy potential. The anisotropic strain energy storage prior to grain crushing leads to the rotation and distortion of the yield surface of cemented granular materials. Parametric analyses are performed to assess the overall capability of the model to characterize the anisotropic inelastic processes in cemented granular. It is shown that the proposed model can accurately predict the strong correlation between anisotropic elasticity and breakage-damage processes in cemented granular materials. When damage involving the skeleton is the dominant inelastic process, the size of the elastic domain contracts and the material exhibits augmented brittleness with the disintegration of cement. While breakage processes are predicted to dominate the response of lightly cemented granular materials resulting in hardening behaviour. This work can be further extended to dynamically capture the anisotropic response of cemented granular materials with water-sensitive mineral constituents by accounting for the evolution of microstructural anisotropy.
Rock mass substitute geometry theory (SGT) and 3D centroid sliding pyramid (CSP) method
Authors: Wu Wei , Yi Xiaokai , Zhu Hehua
Published: May 2024

Discontinuous analysis methods are typically used for the stability analysis of fractured rock masses with multiple sets of joints. Among various discontinuous methods, the key block theory (KBT) requires less data input, has a higher computational efficiency, and is suitable for wide-ranging engineering applications. Classical discontinuous numerical methods typically require complete boundary information for rock block units. However, current information-gathering methods can only capture information on rock surfaces. The proposed rock mass substitute geometry theory (SGT) overcomes this limitation by using local geometric information to equivalently represent the original geometric body simplifying subsequent analyses. A 3D centroid sliding pyramid (CSP) method is introduced for motion state analysis of a rock block that uses only the collinear faces of a block’s free surfaces. A comparison of CSP with KBT proves that CSP not only addresses the issue of collecting only surface information of rock masses but it significantly minimizes the computation scale. Additionally, a 3D discontinuous analysis program was developed, encompassing the entire process of rock mass information gathering, 3D discontinuous modeling, and 3D CSP analysis. The effectiveness and efficiency of the method were validated using stochastically generated models, while its practical engineering applicability was demonstrated at an engineering site.
Shale fault reactivation during hydraulic fracturing in the Sichuan Basin: Evidence from shear experiments and stress perturbation calculations
Authors: An Mengke , Zhang Fengshou , Yin Zhenyu , Elsworth Derek
Published: May 2024

Induced seismicity triggered during hydraulic fracturing for shale gas exploitation in the Sichuan Basin has aroused wide public concern with these earthquakes closely correlated with the reactivation of faults within the reservoir. The target shale reservoirs in the Sichuan Bain are currently located in the Longmaxi formation. To explore instability on these faults, we conducted shear experiments on simulated fault gouges under hydrothermal conditions to assess frictional stability and also evaluated the stress perturbations resulting from multistage hydraulic fracturing. Experimental results show that the frictional instability on these faults is primarily controlled by both mineral composition and the applied temperatures. With a decrease in the contents of phyllosilicate minerals or an increase in applied temperatures, the shale faults exhibit a transition from velocity-strengthening to velocity-weakening behaviour, indicating the potential for unstable fault slip. The stress perturbations resulting from multistage hydraulic fracturing were calculated from a dislocation model of the fluid-driven fracture. These results show that the stress changes resulting from multistage hydraulic fracturing are sufficient to reactivate adjacent unstable faults in the shale reservoir and trigger the seismicity. Our experimental and modelling results highlight the importance of shale composition, temperature, and stress perturbations on shale fault stability. These results have significant implications for understanding the shale fault instability and the potential triggering of induced seismicity during hydraulic fracturing in the Sichuan Basin.
Modeling the Fracturing Behavior Transition in Fractured Granite under Thermo-Hydro-Mechanical (THM) Condition
Authors: Li Mengyi , Zhang Fengshou
Published: May 2024

An in-depth understanding of the thermo-hydro-mechanical (THM) effects on rock fracturing becomes progressively important in natural energy exploitation projects. However, the failure mechanisms of fractured granite under THM conditions are very complex. To investigate the effect of THM treatment on the meso-macro fracturing behavior transition in fractured granite, a coupled thermo-hydro-mesostructure-based DEM (T-H-MSBM) model was developed to reconstruct rock microstructures and distinguish the THM responses of varying mineral grains, pores and micro-cracks in the fractured granite. Based on the T-H-MSBM, fractured granite was first generated in terms of large damage degree, and the comparisons of numerical compression simulations in the natural and fractured granites were carried out under the coupled conditions of temperature (25-225 °C) and pore pressure (0-12 MPa). The interplay of THM treatment and damage degree on the mechanical properties of fractured granite was revealed, and the main mechanisms affecting the varied macro mechanical properties were further discussed insight from the fracturing behavior transition in fractured granite during the THM-uniaxial loading process. The results indicate that both temperature and pore pressure exert the amplified deteriorating effect on the macro mechanical properties of fractured granite with increasing damage degree, while the temperature dependence becomes significantly more pronounced in the fractured granite with low damage degree. The unique distribution of initial cracks controlled by mineral characteristics can lead to large variability in the initiation of THM-induced tensile cracks, and hence to the emergence of multiple fragments in the fractured rock with large damage degree during the compression loading, especially under high pore pressure. The findings can provide important insights into geotechnical applications to achieve engineering safety and economic objectives. For example, during the process of deep resource extraction, we can adjust the reservoir reformation methods in a more reasonable and dynamic manner by considering the variations in the damage degree of fractured rock resulting from excavation disturbance.
Mechanical properties of nano-modified foamed cement paste
Authors: Zhang Z , Gao R F , Wang M Y , Ye G B , Liu S M
Published: May 2024

Foamed cement paste has been increasingly used as backfilling material in practice. The unique porous structure characteristic significantly influences the mechanical properties of foamed cement paste. This study conducted a series of laboratory tests to investigate the mechanical properties of nano-silica modified foamed cement paste. Foamed cement paste specimens with densities of 0.6 g/cm3 1.1 g/cm3 1.5 g/cm3 were prepared, incorporating nano-silica in varying concentrations from 1 g/L to 5 g/L. The density test and uniaxial compression test were conducted. The results show that the nano-silica improved the density inhomogeneity of the foamed cement paste and increased the peak strength. The optimal nano-silica content was 3 g/L in this study. This study offers a practical approach for enhancing the performance of foamed cement paste in engineering applications.
Research on shear characteristics of pile–soil interface under cyclic loading
Authors: Zhou Jie , Zhu Kefan , Liu Chengjun
Published: May 2024

Offshore wind turbine constructions are developing rapidly in China. Generally, large-diameter rigid steel piles are used in offshore wind turbine foundations. However, existing design methods for pile foundations with bearing capacity are often based on small-diameter flexible piles and are inapplicable to real situations. Simultaneously, thick layers of clay cover the fields. Therefore, the shear characteristics of pile–clay interface require examination to optimize design methods. A large-scale interface shear test model corresponding to laboratory tests is established using PFC software, and the micro-parameter values are validated. The simulation results well follow the laboratory test results, and the model accurately reflects pile–clay interactions during shearing. Based on the simulation model, the shear characteristics of the steel–clay interface under different normal loads, cyclic load frequencies, and cyclic load amplitudes are analyzed. With an increase in normal load, the shear strength of the steel-clay interface increases gradually, whereas it slightly decreases with an increase in the cyclic load frequency and amplitude; particularly, the effect of amplitude is significant. The mechanical response of clay at a mesoscopic scale is analyzed. Results show that the greater the normal load, the greater the horizontal displacement of particles. However, the influence of cyclic load frequency and amplitude is the opposite: normal load does not change the contact force distribution of soil particles, and clay volume change is determined by the normal load. Thus, this study provides support for bearing capacity prediction of offshore wind farm pile foundations.
Numerical model for suction anchor under vertical impact loading
Authors: Xu M T , Rui S J , Zhang S H , Zhang Y R , Guo Z
Published: May 2024

In marine engineering, suction anchors are widely employed as the supporting foundation for many types of fixed or floating structures. One of the important control conditions for the service of marine foundations is the impact loading in extreme environments. This study proposes a numerical model to predict the dynamic behavior of suction anchors under impact loading. A mass module is added to the numerical model to quantify the effect of anchor inertia. The t-z springs are positioned along the depth to reflect the soil layer stress and accurately calculate the skirt wall friction. Considering the seepage effect, the differential pressure development, internal soil stress loss and external soil stress enhancement are also reflected. Subsequently, the influence of anchor aspect ratio and loading history are investigated. As the foundation uplift movement is further pronounced, the friction resistance gradually works, resulting in the weakening of inertial force. The existence of pretension loading makes friction resistance take effect earlier, and accelerates its attenuation during the impact loading stage.