bluuebunny/crossref_metadata_2025 huggingface dataset:
A new stegosaur (Dinosauria: Ornithischia) from the Middle Jurassic of Gansu Province, China
Authors: Ning Li , Maidment Susannah C. R. , Daqing Li , Hailu You , Guangzhao Peng
Published: July 2024

Stegosaurs are a minor but iconic clade of ornithischian dinosaurs, yet due to a poor fossil record, their early evolution is poorly understood. Here, we describe a new stegosaur, Baiyinosaurus baojiensis, gen. et sp. nov. from the Middle Jurassic Wangjiashan Formation of the Pingchuan District, Baiyin City, Gansu Province, China. The frontal of Baiyinosaurus possesses a unique characteristic among Stegosauria: it is wider than long and contributes to both the medial and anterior margins of the supratemporal fenestra. The character combinations of dorsal vertebrae of Baiyinosaurus are also different to other stegosaurs: its neural arches are not greatly elongated, its parapophyses are well developed, and its neural spines are axially expanded in lateral. The features of the frontal and vertebrae of Baiyinosaurus are reminiscent of basally branching thyreophorans, indicating that Baiyinosaurus is transitional in morphology between early thyreophorans and early-diverging stegosaurs. Systematic analysis shows that Baiyinosaurus is an early-diverging stegosaur.
Localized thermal levering events drive spontaneous kinetic oscillations during CO oxidation on Rh/Al2O3
Authors: Decarolis Donato , Panchal Monik , Quesne Matthew , Mohammed Khaled , Xu Shaojun , Isaacs Mark , Clark Adam H. , Keenan Luke L. , Wakisaka Takuo , Kusada Kohei , Kitagawa Hiroshi , Catlow C. Richard A. , Gibson Emma K. , Goguet Alexandre , Wells Peter P.
Published: July 2024

Unravelling kinetic oscillations, which arise spontaneously during catalysis, has been a challenge for decades but is important not only to understand these complex phenomena but also to achieve increased activity. Here we show, through temporally and spatially resolved operando analysis, that CO oxidation over Rh/Al2O3 involves a series of thermal levering events—CO oxidation, Boudouard reaction and carbon combustion—that drive oscillatory CO2 formation. This catalytic sequence relies on harnessing localized temperature episodes at the nanoparticle level as an efficient means to drive reactions in situations in which the macroscopic conditions are unfavourable for catalysis. This insight provides a new basis for coupling thermal events at the nanoscale for efficient harvesting of energy and enhanced catalyst technologies.
Trends in polyacrylamide utilization and treatment for hydraulic fracturing
Authors: Zhong Cheng , Chen Rong , Liu Baicang , Pu Shengyan , Hou Deyi
Published: July 2024

Polyacrylamide (PAM) and its derivatives play a pivotal role in various facets of hydrocarbon development. Proper application and treatment of PAM have the potential to enhance hydrocarbon production efficiency while mitigating adverse environmental effects. This perspective highlights the growing concerns surrounding the increased challenges associated with PAM treatment, particularly driven by the increasing usage of PAM during the transition in extraction sites from conventional to unconventional reservoirs. We delineate current limitations in existing materials and technologies employed for PAM treatment and propose key recommendations as crucial avenues for improvement. These recommendations include exploring green polymer alternatives and fluid systems, conducting pre-assessments of chemical selections, adopting advanced membrane filtration and biological treatment materials and technologies. The primary objective of this perspective is to draw attention to the current issues in PAM utilization and treatment, providing contemporary solutions for more sustainable hydrocarbon extraction.
Wideband coherent microwave conversion via magnon nonlinearity in a hybrid quantum system
Authors: Wu Jiahao , Liu Jiacheng , Ren Zheyu , Leung Man Yin , Leung Wai Kuen , Ho Kin On , Wang Xiangrong , Shao Qiming , Yang Sen
Published: July 2024

Frequency conversion is a widely realized physical process in nonlinear systems of optics and electronics. As an emerging nonlinear platform, spintronic devices have the potential to achieve stronger frequency conversion. Here, we demonstrated a microwave frequency conversion method in a hybrid quantum system, integrating nitrogen-vacancy centers in diamond with magnetic thin film CoFeB. We achieve a conversion bandwidth ranging from 0.1 to 12 GHz, presenting an up to 25th order frequency conversion and further display the application of this method for frequency detection and qubits coherent control. Distinct from traditional frequency conversion techniques based on nonlinear electric response, our approach employs nonlinear magnetic response in spintronic devices. The nonlinearity, originating from the symmetry breaking such as domain walls in magnetic films, presents that our method can be adapted to hybrid systems of other spintronic devices and spin qubits, expanding the application scope of spintronic devices and providing a promising on-chip platform for coupling quantum systems.
Management and prevention of in-hospital cardiac arrest: present and future
Authors: Vo Jonathan , Norby Faye L. , Marano Paul , Matusov Yuri , Reinier Kyndaron , Ebinger Joseph , Halperin Henry , Chugh Sumeet S.
Published: July 2024

Cardiac arrest is most commonly defined as the cessation of cardiac mechanical activity requiring either delivery of chest compressions and/or defibrillation. The condition is often subdivided into in-hospital cardiac arrest (IHCA) and out-of-hospital cardiac arrest (OHCA) based on different locations, but also differences in epidemiology, natural history, co-morbidities, process of care, and provider characteristics. Both are complex conditions that warrant ongoing research to improve management, but IHCA appears to have received disproportionately less investigative attention. Recent reviews of over 150 randomized controlled trials (RCTs) conducted between 1995 and 2019 reported that the vast majority (>80%) were focused on OHCA, approximately 10% on both and <10% were focused solely on IHCA. In this review, we will provide an overview of current knowledge regarding IHCA epidemiology, management and prevention, while also identifying opportunities for future research.
Optimizing interface concentration and electric fields for enhanced lithium deposition behavior in lithium metal anodes
Authors: Liu Jiaxiang , Hua Haiming , Lin Jie , Deng Yongliang , Pei Nanbiao , Zhang Peng , Dong Jin-Chao , Li Jian-Feng , Zhao Jinbao
Published: July 2024

A high-anion-concentration interface, immobilizing a high concentration of anions at electrolyte/electrode interface, can alleviate formation of space charge layer with uneven electric field distribution and inhibit the growth of Li dendrites.
Dual aggregation-induced emission enhancement (AIEE) and crosslink-enhanced emission (CEE) driven via halogen-bond-assisted cocrystallization and radical solid-phase polymerization
Authors: Le Hong Tho , Stanley Chelsea Violita , Goto Atsushi
Published: July 2024

Concurrent emission enhancement was attained by halogen-bond-driven cocrystallization (aggregation-induced emission enhancement, AIEE), followed by halogen-bond-driven (non)covalent crosslinking of polymer (crosslink-enhanced emission, CEE).
Effect of a mesoporous NiCo2O4 urchin-like structure catalyzed with a surface oxidized LiBH4 system for reversible hydrogen storage applications
Authors: Kaliyaperumal Ajaijawahar , Periyasamy Gokuladeepan , Kombiah Iyakutti , Annamalai Karthigeyan
Published: July 2024

Surface oxidized LiBH4/NiCo2O4 systems prepared by wet-impregnation method. LiBH4 + 75% NiCo2O4 released 5.8 wt% H2 at 250 °C in 60 min. The increased concentration of NiCo2O4 in all the systems impacts the active sites and H2 storage capacity.
MOFabric: an effective and wearable protective garment towards CWA detoxification
Authors: Balasubramanian Selva , Kulandaisamy Arockia Jayalatha , Das Apurba , Rayappan John Bosco Balaguru
Published: July 2024

UiO-66 and UiO-66-NH2 functionalized cotton fabrics (MOFabrics) confer the ability to self-detoxify and serve as protective garments.
Lewis acid-catalyzed diastereoselective formal ene reaction of thioindolinones/thiolactams with bicyclobutanes
Authors: Guin Avishek , Deswal Shiksha , Harariya Mahesh Singh , Biju Akkattu T.
Published: July 2024

The synthetic potential of BCBs as enophiles in a mild and diastereoselective Sc(OTf)3-catalyzedformalene reaction with thioindolinonesto afford 1,3-disubstituted cyclobutanes isreported.
Angular scattering measurements and modelling from building surfaces at sub‐THz frequencies between 92‐110 GHz
Authors: Serghiou Demos , Khalily Mohsen , Brown Tim , Tafazolli Rahim
Published: July 2024

This letter presents experimental angularly resolved measurements and a model framework for characterizing continuous wideband reflection coefficients at sub‐terahertz frequencies between 92 and 110 GHz. Surfaces that appear “smooth” but with internal features comparable to the wavelength have shown to cause frequency selective scattering. An nth‐degree polynomial regression model is employed to quantify non‐linear multi‐path scattering that cannot be described by a best‐fit line, with least‐squares regression applied to find the best‐fitting polynomial and hence the coefficients. The obtained coefficients are then validated against the delay domain statistics of the propagation channel, demonstrating the proposed model's good agreement with measurements and its efficiency in reproducing angle‐dependent reflection coefficients for use in ray‐tracing tools.
Research on efficient design method of high torque motor with dual airgap hybrid rotor for aircraft engines
Authors: Yu Siyang , Xu Yingjie , Zhang Yue , Liu Guangwei , Zhang Fengge
Published: July 2024

High torque density and high reliability motors have a wide application prospect in aerospace field, so a hybrid rotor and dual stator motor is studied in this paper. Firstly, to address the problem that the difference in power density between the inner and outer unit motor is so large that it is not suitable for electromagnetic design using the power splitting method, a main dimensioning calculation method based on the equal‐power volume transformation is proposed. The influence of thermal load on the output performance of the inner and outer unit motors is taken into account comprehensively. The main dimensioning expressions for such motors are derived. Secondly, the output performance consistency between the inner and outer unit motors is theoretically analysed, and the optimal angle between the d‐axis of the permanent magnet rotor and the d‐axis of the reluctance rotor is obtained when the motor is operated in the maximum torque per ampere control mode. Finally, a prototype with a rated power of 46.7 kW was developed and load experiments were conducted on it, and the experimental results verified the correctness and feasibility of the theoretical analysis method.
Combined scheme for mitigating coupling interference in dual‐band shared‐aperture base station antenna
Authors: Lu Xiaochi , Wang Jiahao , Zhao Yanwen , Zhao Dexin
Published: July 2024

A dual‐band shared‐aperture antenna array is presented, involving a combined scheme to suppress mutual coupling interference. The proposed array is comprised of a low‐band (LB) antenna, a frequency selective surface (FSS), sixteen high‐band (HB) antennas, and a reflector. The LB antenna utilises electromagnetic transparent (ET) characteristics to minimise scattering interference, while the FSS isolates resonance interference and port signal interference. The combined scheme integrates the benefits of both the ET antenna and FSS to suppress mutual coupling interference effectively. A prototype of the proposed antenna was fabricated and measured, operating at 1.7–2.7 GHz and 3.3–3.9 GHz. The simulated and measured results demonstrate stable patterns for both the LB antenna and the HB antennas. The cross‐band isolation is higher than 28 dB in the low‐band. With these advantages, the antenna array is suitable for base station applications.
Evaluation of non-uniformity of sandy soil specimens compacted in the field and laboratory using triaxial tests
Authors: Tomita Yuichi , Koseki Junichi
Published: July 2024

The strength and deformation characteristics of compacted soils are typically evaluated using triaxial compression tests on specimens that are compacted relatively uniformly in a laboratory. Soil compacted in the field using vibration rollers is nonuniform in the vertical depth direction; this is because the gradient of the dry density and saturation degree in the depth direction of each compaction layer is large, owing to the distribution of the load transmitted from the contact surface. As a quality control method for earth-filling works, nondestructive inspection indices—such as the soil stiffness index—are applied in some cases, and the average value of the nonuniform compaction layers is measured. Further, unsaturated specimens, which were retrieved from the test fill yielded during field compaction tests, and specimens obtained via compaction using the same soil as that in the laboratory were prepared, and then triaxial compression tests were performed. Local displacement transducers were installed to obtain local deformation characteristics, based on the vertical depth of the specimen, which were then compared with the average deformation characteristics of the entire specimen. The results show that the local low-stiffness section significantly affects the overall average; this makes it non-negligible because the specimen compacted in the field is nonuniform. However, because field-compacted soil has a local lowstiffness section near the surface layer compared with laboratory-compacted soil, evaluations based on the nondestructive inspection of the surface layer may result in underestimations.
Influence of time on the small strain shear modulus of an allophanic volcanic ash
Authors: Gobin Mukteshwar , Yasufuku Noriyuki , Watanabe Midori , Liu Guojun , Ishikura Ryohei
Published: July 2024

The small strain shear modulus is an important parameter in the assessment of soil dynamics problems. Studies on the small strain shear stiffness of volcanic ash remain rare probably because globally they cover just under 1% of the land surface. However, on a regional scale, this figure may be consequential as in the case of Japan, where about one third of its total land surface is covered by andosols. In this research, we aimed at understanding the influence of confinement time, a non-negligible parameter, contingent on the soil type, which needs to be accounted for when assessing the shear modulus. Bender element tests were conducted on allophanic volcanic ash, kuroboku soil sampled from the southern island of Kyushu in Japan. The allophanic ashes present all the characteristics of a non-textbook soil, notably high natural water content, high liquid and plastic limits and high void ratios. From the micrographic images, it was observed that the soil structure consisted of different types of porous particles (allophane, imogolite, volcanic glass and so on) at different internal spatial scales. Strong electrostatic bonding between the allophane particles means that in normal conditions the soil material exist as aggregates. The consequence is that the end of the consolidation stage is reached within a few minutes. Thus, the threshold demarcating the onset of the creep stage is different compared to sedimentary materials or other clayey soils. Based on the test results, empirical equations for predicting the time-dependent behaviour of the shear modulus were proposed.
Pore-scale precipitation pattern and grain-scale cementation strength by microbially induced calcium carbonate precipitation (MICP)
Authors: Kwon Tae-Hyuk , Ham Soo-Min , Baek Seung-Hun , Han Gyeol , Martinez Alejandro , DeJong Jason
Published: July 2024

Microbial induced calcium carbonate precipitation (MICP) is widely investigated as a sustainable method of soil improvement. The pore-scale precipitation habit of calcium carbonate (CaCO3) and the grain-scale mechanical strength of the cementing bonds play a significant role in determining the mechanical response of MICP-treated soils. This study presents the pore-scale precipitation patterns in MICP-treated sands and the grain-scale cementation strength of two beads cemented by MICP. X-ray computed microtomography imaging of MICP-treated sands with different grain sizes reveal that the surface area, number of contacts, and flow-induced shear detachment as well as bacterial cell loci have a profound effect on the pore-scale precipitation. With different grain size, the precipitation can show either a contact-cementing pattern or a surface-coating habit. Particularly, evolution of the precipitation pattern is observed for large-sized grains from the surface-coating mode to the contact-cementing mode with an increase in CaCO3 content. The grain-scale mechanical strength tests on MICP-bonded bead pairs demonstrate that the failure with MICP bonding occurs in three modes: debonding, internal, and mixed failure modes. Amongst, the debonding failure mode has the greatest strength and the internal failure mode shows the lowest strength. The tensile strength is greater than the shear strength in all modes; particularly in debonding failure mode, the tensile strength of ~35 kPa and shear strength of ~13 kPa. The presented results advance our insight into pore-scale and grain-scale behavior of MICP-treated sands, which can be further extended to develop DEM models and transport models.
Use of computer vision to analyze cyclic loads on the Guamo sand
Authors: Gil Diego , Mendoza Cristhian , Vasquez-Varela Luis
Published: July 2024

Some effects have been evidenced during several earthquakes around the world. For example, the liquefaction phenomenon, and structural collapse, among others. However, granular soil behaviour during this event has not been completely understood; this is proved by the number of investigations in physical models, constitutive models, and laboratory testing proposals about this topic. A question appears at this point: when do the effects take place? To cope with this issue, it is proposed to create an experimental model composed of a Single Degree of Freedom Oscillator (SDOFO) designed to try to assess the liquefaction. Likewise, the device could transmit cyclic loadings to the soil. This SDOFO was an electromechanical oscillator servo-controlled appropriated to manage the frequency of excitation and amplitude of the oscillatory movement. The measurement methodology was based on computer vision using Open CV by Python, which allowed measuring displacements and times of the SDOFO instead of using LVDT sensors located directly at the actuator; thus, computer vision permitted a “free movement” of the actuator similar to the actual behavior of buildings in seismic events. The samples required for this study were the Guamo sand collected in a natural deposit in Colombia (South America) and the Ottawa sand to compare results. A simple criterion was used to try to determine the possible liquefaction onset. It was defined based on the evolution of displacements relying on the number of cyclical loads. According to the results, it was able to define that the relationship between the excitation frequency, the amplitude of the oscillatory movement, and the number of cycles required to reach the possible liquefaction state was inverse.
2T3C apparatus and DIC technology to investigate the thermomechanical behaviour of the interface between bituminous layers
Authors: Tran Thien Nhan , Mangiafico Salvatore , Sauzéat Cédric , Di Benedetto Hervé
Published: July 2024

The bonding at the interface is seen in most road structure design methods as perfectly bonded and this ideal condition is supposed to last during the whole service life. However, the real working capacity at the interface is complex and gradually degrades because of repeated traffic load and weather conditions. A new apparatus called 2T3C (“Torsion, Traction, Compression sur Cylindre Creux” in French, or “Torsion, Tension, Compression on Hollow Cylinder” in English) was developed at the ENTPE/University of Lyon to investigate the thermomechanical behaviour of the interface between bituminous layers. The sample has two layers of similar or different materials. It has a total height of 125 mm and a wall thickness of the 25mm. The thickness was chosen small enough in order to validate the assumption of quasihomogenous stress and strain fields between inner and outer surface. The DIC technology is performed considering the three listed elements: (1) two couple of cameras are situated on two opposite sides of the sample (4 cameras in total) to take 3D images; (2) a software is employed to calculate the displacements in 3 dimensions of all points in the area of interest; and (3) the strain fields in the 2 layers and the displacement gap at the interface are computed using a method developed at the University of Lyon/ENTPE. In this paper, a focus is proposed on the viscoelastic and fatigue behaviours of the two bituminous layers and of the interface. Small and large numbers of loading cycles are successively considered in the small strain domain.
Investigation of diatomaceous sand using elastic and electromagnetic waves in oedometer tests
Authors: Hoang Ngoc Quy , Kim Sang Yeob , Lee Dongsoo , Lee Jong-Sub
Published: July 2024

The small-strain and electromagnetic behaviors of soils significantly change due to compression. The objective of this study was to investigate the small-strain stiffness and electrical resistivity of diatomaceous sand by modifying the conventional setup of oedometer tests (1D-compression tests). The specimens used were pure sand and sand with 20% diatoms by weight. The vertical displacement was directly observed using a digital gauge at the top of the compression cap during compression. At the end of each loading step, shear waves (S-waves) are measured using a pair of bender elements installed on the top and bottom compression caps. In addition, electrical resistance was measured using a pair of electrodes installed horizontally in the middle of the compression cylinder. The test results show that the compression index increased but the swelling index decreased according with the increase in the amount of the small and crushable diatom particles. The presence of diatom particles weakened the interparticle contacts and softened the soil skeletons. In addition, the electrical resistivity increased with the increase in diatom contents, which increased the surface conduction. Our work suggests that the S-wave velocity and electrical resistivity of diatomaceous sand can be characterized by modifying the conventional oedometer tests.
Interfacial characterization of soil-3D printing materials
Authors: Fadaie Sina , Mehravar Moura , Webb David John
Published: July 2024

3D printing has emerged as a revolutionary technique for producing products with specific shapes and mechanical properties tailored to various needs. Its ability to fabricate intricate structures and forms has garnered considerable attention, leading to numerous research efforts exploring its potential benefits in geotechnical applications. These endeavours highlight the possibilities of utilizing 3D printing technology to create innovative and customized materials for soil reinforcement, such as geosynthetics, and fibres, as well as replicating soil particles, physical models of soil structures, and drainage systems in geo-structures. Additionally, beyond its role in geotechnical engineering, the interaction between geo-structures (foundations, retaining walls, embankments, tunnels, piles, infrastructures, etc.) and the surrounding soil under different loading and environmental conditions is of paramount importance. The interface between these structures and the soil plays a critical role in load transfer and overall stability. Therefore, this study focuses on investigating the interface between soil and 3D printed components through direct shear testing. The experimental campaign aims to examine how different factors, including the type of 3D printing materials, material rigidity, and surface texture of the printed components, influence the shear behaviour of the soil-3D printing material interface. The findings suggest that Young’s modulus of the 3D printed materials plays a crucial role in determining the response of the soil-3D printed parts interface. Furthermore, an optimized design is proposed to achieve the desired shearing resistance at the interface. The insights gained from this investigation have practical implications for optimizing the design of 3D-printed components in geotechnical engineering applications.
In-situ material damping measurements using the crosshole seismic method
Authors: Hwang Sungmoon , Stokoe, II Kenneth H.
Published: July 2024

Crosshole seismic testing is commonly used to determine detailed and reliable wave velocity profiles. Material damping measurements can also be performed in crosshole seismic testing, but these measurements require a window function to maintain similar amplitude shapes over the frequency range of interest for the calculation. In-situ seismic testing, including downhole and seismic cone penetration testing (SCPT), also requires a window function for the material damping calculations. However, the length of the window function has the largest influence on the material damping calculation. Therefore, the half-power bandwidth method is introduced to determine the material damping ratio without the window function in crosshole testing by replicating the unconfined, free-free, resonant column (Fr-Fr) test. To demonstrate the influence in the length of the window function, the first cycle of the signal is used in the material damping calculation. The half- power bandwidth method is verified using synthetic signals and field data. Two sets of crosshole and downhole tests were performed, one at a backfill test pad and the second at a Hornsby Bend research site operated by the University of Texas at Austin. The in-situ material damping ratio calculated from these two sets of crosshole tests using the half-power bandwidth method are compare with the Spectral Ratio Slope (SRS) method applied to the downhole testing at these sites. The material damping calculated from the half-power bandwidth method using the full signal results in a reliable and precise damping value compared to the SRS method applied to the downhole data.
Measurement of subgrade soil permanent deformations under repeated loadings during simple in-situ test
Authors: Kuttah Dina
Published: July 2024

is well known that permanent deformation has a significant influence on the performance of pavements because it leads an increase in maintenance operations and costs and reduces ride quality. Therefore, it is important to predict the permanent deformations during the design stage.

Due to the fact that up to date there is no simple test equipment and procedure that enables a direct in-situ measurement permanent deformations of subgrade soil under repeated loading, the current research has been undertaken to evaluating new testing approach to fulfil this requirement. The current study deals with developing a new multifunctional light weight deflectometer (LWD) that can be used to determine the in-situ permanent deformations of subgrade soil due to repeated loading by simple, cheap and time saving testing approach.

It was concluded that the suggested repeated light weight deflectometer test could give a powerful material assessment and pavement design tool for the analysis of compacted subgrade soil used in this study. The developed LWD that can measure the permanent deformations directly could be utilized to establish the risk level of permanent deformations in subgrade soil in pavement constructions during the design and construction stages.
Disturbance of sand samples obtained by piston samplers and ground freezing
Authors: Quinteros Santiago , Carraro Antonio , L’Heureux Jean-Sébastien , Berggren Anne-Lise
Published: July 2024

High quality sampling of sand and silty sands is extremely challenging. Undisturbed samples of sand can be obtained by means of very expensive and time-consuming techniques such as ground freezing. Given the high costs and expertise required to obtain undisturbed sand samples through ground freezing, piston sampling techniques are usually used in engineering practice. This paper summarises the experiences, technical difficulties, disturbance analyses and issues encountered during sand sampling at the Norwegian Research Site at Øysand using piston sampling and ground freezing technology. Two state-of-the-art piston samplers were used (NGI-Geonor composite piston sampler and Geonor K-200 thin-wall push piston sampler) along with the state-of-the-art Japanese gel push piston sampler. Ground freezing was successfully achieved also both on sands and silty sands at Øysand. Sample disturbance was assessed qualitatively and quantitatively through analysis of micro-computed tomography images. Results from these analyses provide an overview of the strengths and weaknesses of the three piston samplers in comparison with ground freezing, together with recommendations for sampling of sands using piston techniques.
Characterisation of the heterogeneity of a sand specimen in triaxial compression using x-ray CT and representative elementary volumes
Authors: Schmidt Selma , Wiebicke Max , Herle Ivo
Published: July 2024

Standard laboratory tests, such as the triaxial test, are often considered to be element tests. But, when observing such a test, it becomes obvious that this assumption of homogeneity is far from accurate. The localisation of strain is often visible to the naked eye and becomes even more obvious when observed on the grain scale. Other variables, such as those describing the soil fabric, are expected to localise as well. In this work, two sand samples are analysed at different loading states regarding the heterogeneity of three soil variables: void ratio, coordination number and contact orientation anisotropy. For this purpose, the size of a Representative Elementary Volume (REV) is determined using three criteria: the convergence of the mean and variance of the variables with increasing element size as well as a χ2-test. The size of the REV is varying depending on the chosen variable but almost the same for the two specimens when related to the mean grain diameter d50. The REV is placed in a regular grid throughout the specimen and the three variables are determined for each REV. The stochastic as well as spatial heterogeneity is identified for each specimen. As one of the samples is analysed for different loading states throughout a triaxial test, the evolution of the soil heterogeneity is identified. A localisation of all three variables can be observed at the end of the triaxial test as well as a strong initial heterogeneity for both sand samples.
Sensitivity of G0 and stress-strain relation of geomaterials to grain shape and surface roughness
Authors: Otsubo Masahide , Li Yang , Kuwano Reiko
Published: July 2024

It is empirically known that the packing property and mechanical responses of cohesionless granular materials are influenced by grain shape. For example, the attainable range of void ratio depends on grain shape; angular materials tend to exhibit greater friction angles. Besides, shear wave velocity (Vs ) and small-strain shear modulus (G0 ) of sphere assemblies are affected by surface roughness. However, consensus has yet to be reached on the combined effect of grain shape and surface roughness on G0 and stress-strain relation. This contribution aims to evaluate the shape-roughness combined effect on the strain-dependent mechanical responses of granular materials. Three groups of glass beads having different grain shapes and a silica sand were used, and their grain surfaces were roughened through a systematic procedure using a milling machine. In total, eight materials were subjected to triaxial compression after measurement of Vs. The experimental results reveal that the stress-strain relation of angular particles is remarkably affected by the surface roughness, whereas the roughness effect on the stress-dependent variation in G0 is limited for angular particles.
Effect of soil structuring on stiffness evaluated by triaxial and seismic flat dilatometer tests
Authors: Rodrigues Carlos , Cruz Nuno , Almeida e Sousa Jorge , Lemos Luís
Published: July 2024

Granitic residual soils are considered structured soils. The bonding between the particles and the fabric inherited by the original rock play an important role in controlling the mechanical behaviour. These materials considered as “cemented” soils are often seen as non-textbook materials, since they do not fit into the usual behaviour of transported soils in the light of classical Soil Mechanics theories. To study the stiffness of the granitic residual soils located in Guarda (northeast of Portugal) several SDMT tests carried out on structured soils (natural granitic residual soils and artificial cemented soils) and triaxial tests (carry out with internal instrumentation), performed on samples collected at the same depth, at similar confining stresses, to those involved in the SDMT tests. The results show that in the stiffness decay curve the value of the stiffness modulus (EDMT or GDMT) increase with the increasing level of cementation. In addition, the strain levels involved in the calculation of the stiffness modulus (EDMT or GDMT) decreases with the increase of the cementation level, which can have important consequences for practical purposes of geotechnical design.
Effect of soil-pile contact parameters on pile bearing capacity value
Authors: Campos Darym , Morandini Thiago , Ferreira Stéphanie , Camapum José , Cavalcante André , Ozelim Luan
Published: July 2024

The soil and foundation elements are fundamental to the behavior of a structure. When the foundation soil has a low capacity, it is necessary to transmit the loads to a deeper and more resistant layer, using deep foundations. A pile load test is a field measurement of the bearing capacity (vertical or horizontal) of a foundation element. In addition to a physical model of a load test, the use of computational tools can bring additional understanding. In order to analyze the responses obtained by numerical models compared to field test results, tools that use Finite Element Methods (FEM) and that have a series of constitutive models become a great alternative. This paper aims to study the behavior of Continuous Flight Auger (CFA) piles, aiming to understand the soil-pile interaction regarding the effect of soil-pile contact parameters on pile bearing capacity value. In this way, experimental data from three load tests were compared with numerical simulations using the Mohr-Coulomb constitutive model. Also, a parametric study was completed based on the collected soil data from the literature of the region that most affected the settlement behavior of the load pile. It was concluded that there is a direct and significant influence of the friction coefficient on the pile bearing capacity. In addition, by incorporating more real soil data and parameters representing its actual formation, the results of the pile load test simulation can be taken as an alternative to estimate the ultimate capacity of a vertically loaded pile in the absence of the static load test, which has been widely observed in engineering practice.
Clay micromechanics: Numerical modelling of electrical double-layer interactions to develop particle-based models for clay
Authors: Casarella Angela , Donna Alice Di , Chassagne Claire , Tarantino Alessandro
Published: July 2024

Discrete element modelling of clays requires defining the interaction energy between two particles. The Derjaguin, Landau, Verwey and Overbeek (DLVO) theory combining the effect of the van der Waals forces and the Coulombic forces due to the double layer of counterions provides a widely accepted framework to characterise the pair potential energy. Solutions of the Poisson-Boltzmann (PB) equation to quantify the Coulombic forces are only available for the case of infinitely extended and uniformly charged facing plates (1D conditions). However, these assumptions are not representative of a clay particle system. Particles should be represented by platelets of finite size and finite thickness, with different charges between the edge and the basal planes. This paper addresses the problem of deriving the Coulombic interaction forces for plates of finite size and thickness in 3D configuration by solving the Poisson-Boltzmann equation numerically via the Finite Element Method (FEM). It is shown that 2D particles (plates of infinitesimal thickness) provide an adequate representation of Coulombic interaction as long as the particles are uniformly charged. The advantage of 2D particles is to reconcile numerical modelling with analytical solutions available in the literature. The use of 2D particles is questionable when considering different charges between basal planes and edges.
Numerical modelling of under-reamed scaled-down piles by water jet driving
Authors: Ruver Cesar Alberto
Published: July 2024

Water jet pile driving technique has been shown to be viable for driving precast piles in highly resistant soil layers. However, the use of this technique drastically reduces the pile load capacity. On the other hand, the use of under-reamed precast piles improves the vertical load capacity. The objective of the present paper is to show the efficiency of the use of under-ream, through the numerical modelling of load tests carried out in laboratory scaled-down models. For numerical modelling, finite element method (FEM) was used. Through numerical analysis, it was possible to identify the distribution of stresses and strains at the toe, shaft, and under-reams. With that it was possible to identify and check the contribution of these in the total vertical compressive load capacity. It was possible to verify that the under-reams contribute to the vertical load capacity varying from 47% to 57% depending on the configuration, number, and distribution of the underreams along the pile. Thus, increasing the final vertical load capacity, if compared to piles without under-ream (uniform shaft). Numerical modelling proved to be a fundamental tool, which made it possible to show the mechanisms involved in the action of under-ream in increasing the vertical load capacity of piles.
In situ ageing of a lime/cement-treated expansive clayey soil
Authors: Chabrat Nicolas , Cuisinier Olivier , Masrouri Farimah
Published: July 2024

This paper focuses on the performances of a treated expansive clayey soil sampled on an embankment constructed in 2010. Two types of treatment used during construction are considered: 4% lime as well as a mix of 2% lime and 3% cement. Oedometer tests were carried out on different parts of the embankment, to assess the compressibility of the soil. The results were compared to the compression curve of the untreated soil, also sampled in the same embankment. Several complementary aspects were also investigated (moisture content, dry density,…) to assess the ageing process of the embankment. The obtained results showed that the behaviour of the material from the outer part of the backfill is similar to the mechanical performances of the untreated soil, demonstrating a strong alteration of the effect of both treatments. This alteration is noticeable until a horizontal distance of about two meters from the surface. Beyond this distance, the performance of the soil is comparable to the mechanical behaviour of treated soil. These observations, similar for each treatment dosage, tend to question the durability of the treatment at the edge of the earth structure.
The effect of key parameters on the mechanical response of artificially cemented iron ore tailings for dry stacking purposes
Authors: Consoli Nilo Cesar , Delgado Bruno Guimarães , Silva João Paulo Sousa , Scheuermann Filho Hugo Carlos
Published: July 2024

Regulations prohibiting the construction of new tailings dams using the upstream method and requiring the closure of the existing ones have been recently introduced in Brazil. This scenario demands the sought for alternatives to manage both the previously disposed tailings as well as the upcoming generated mining residues. Fortunately, advances in dewatering technologies have enabled the tailings’ dried disposal in stacks having hundreds of meters rather than the traditional slurry deposition. Eventually, a cement material can be incorporated into the tailings before the stacking aiming to enhance the overall material’s performance, permitting the construction of higher and more inclined piles. In this regard,the present study evaluates the effect of key variables on the stiffness and strength of compacted iron ore tailings-cement blends. Specifically, the effect of the following variables was statistically evaluated through a full factorial design set: dry unit weight (17, 18, and 19 kN/m3), amount of cement (1, 3, and 5%), curing period (7, 28, and 90 days) and cement type (pozzolana Portland cement and high early strength Portland cement). The results have shown that all the main factors, and most of the second-order interactions, were significant in altering both the strength and stiffness of the studied mixtures, with a highlight to the amount of cement, curing time, and dry density. The type of cement, in turn, has exerted a marginal influence. As well, both responses could be successfully correlated to the adjusted porosity/cement index via power-type functions.
Effect of large particle content on strength and failure mode of binary granular mixture in shear under plane strain condition
Authors: Taue Masato , Nakata Yukio , Kajiyama Shintaro
Published: July 2024

The strength and failure modes of binary granular mixture composed of two different sized particles, such as gravel and sand, vary depending on the content of gravel (large particle content). The binary granular mixture structures are classified into small particle skeleton structure, intermediate skeleton structure, and large particle skeleton structure, depending on the large particle content. The authors propose a microscopic model to evaluate the range of large particle content in the intermediate skeleton structure, and confirm its applicability in Angle of reposed experiment. Parameters obtained from the experiment, such as “ peak principal stress difference” and “ principal stress difference at large axial strain” as strength, “ shear band slip angle” and “shear band width “ as failure mode, were discussed for large particle content. The results showed that the large-particle content of the intermediate skeleton ranged from 8.7% ~ 52.7% for the peak principal stress difference, 3.2% ~ 44.1% for the principal stress difference at large axial strain, 12.0% ~ 77.3% for the shear band slip angle, and 4.1% ~ 81.2% for the shear band width. The microscopic model calculated range for the intermediate skeleton structure was 2.3%~66.4%, which is generally wider than the experimental results under confining pressure. The microscopic model gives the range of the initial (sedimentary) state of the intermediate skeleton structure. It is inferred that the range of the intermediate skeleton structure narrows with increasing confining pressure. Therefore, the microscopic model should take into account the effect of confining pressure.
The apparent viscosity to model the behaviour of liquefied sands
Authors: Mele Lucia , Lirer Stefania , Flora Alessandro
Published: July 2024

The liquefaction induced loss of soil strength and stiffness marks a change of soil state, that switches from solid to liquid. Recently, the research has revealed that when liquefaction is attained, the soil behaves as a non-Newtonian fluid. Therefore, the framework of soil mechanics cannot be adopted and then the soil behaviour should be studied using a fluid mechanic approach. Several research works highlighted the large potentiality of the apparent viscosity () as the parameter ruling both the liquefaction triggering and the behaviour of liquefied sands. Mele (2022) showed that liquefied sands exhibit a shear-thinning behavior (i.e. decreasing viscosity with increasing shear strain rate), highlighting the direct link between k and n (parameters of shear-thinning model) to the soil demand (CSR). This paper aims to confirm the proposed correlations of Mele (2022) passing from small to full scale. To do that, the results of 1D non-linear site response analysis of the well-known case study of Treasure Island (California), affected by extensive liquefaction phenomena during the 1989, have been studied and interpreted with a “viscous perspective”. The good agreement of the calibrated pseudo-plastic law with the results of the dynamic analysis confirms, the relevance of as physically based parameter for the correct modeling of the behaviour of liquefied sandy soils.
Applicability of shear wave velocity to evaluate state of granular materials with fines
Authors: Lipiński Mirosław J. , Wdowska Małgorzata , Puspitaningrum Intan
Published: July 2024

Evaluation of state of cohesionless soils is a key issue in majority of geotechnical projects, especially when the major concern is liquefaction phenomenon. Standard approaches based on static or dynamic penetration tests are of limited or no use in granular materials containing considerable amount of fines. Therefore, there is a need to look for alternative approaches to identify state of materials containing certain amount of fines. One of a conceivable approaches rests on shear wave velocity (Vs) measurement. It results from the fact that Vs reflects state of stress and void ratio as well. A little is known to what extent shear wave velocity might reflect state of soil, especially, when it contains certain amount of fines. The paper concerns possibility of evaluation of state of cohesionless soils containing fines on the basis of shear wave velocity. The approach is based on hybrid approach i.e. laboratory and field measurement of shear waves velocity which enables projection of correlation between void ratio and normalized shear wave velocity measured in the laboratory for a given soil on a field profile. Thus, the determined void ratio profile is used to determine undrained shear strength on the basis of steady state line determined in the laboratory for the same soil batch. This procedure was carried out for twokinds of soil containing 10 and 36% of fines, which represent a sand-like material and transition zone behavior. Comments concerning applicability of this approach are given in the conclusion.
CPT-based design of pile foundations in sand and clay: Perspectives
Authors: Sakleshpur Venkata Abhishek , Prezzi Monica , Salgado Rodrigo
Published: July 2024

This paper provides some perspectives and guidance for the design of pile foundations in sand and clay using cone penetration test (CPT) results. A key variable in the estimation of the limit unit shaft resistance qsL of piles in sand is the critical-state interface friction angle δc, which is a function of the critical-state friction angle ϕc of the sand. In the absence of direct shear or triaxial compression test results, which is often the case for routine infrastructure projects, engineers typically assume a conservative value for ϕc in pile design. In addition, effective stress-based methods for estimation of qsL of driven piles in clay rely on the residual interface friction angle δr, among other variables; however, in these methods, δr does not vary with the normal effective stress on the pile operative at the time of shearing. In this paper, we present relationships and approaches to address these issues. Finally, a relationship between the cone resistance qc and the corrected standard penetration test (SPT) blow count N60 was also developed so that engineers may obtain an estimate of qc for use in a CPT-based design method when only SPT blow counts are available for a site.