bluuebunny/crossref_metadata_2025 huggingface dataset:
Methylene spacer regulated variation in molecular and crystalline architectures of cobalt(iii) complexes with reduced Schiff base ligands: a combined experimental and theoretical study
Authors: Banerjee Abhisek , Frontera Antonio , Chattopadhyay Shouvik
Published: June 2019

The differences in the molecular and crystalline architectures of two heteronuclear cobalt(iii)/sodium complexes were correlated with the relative dispositions of NH groups in them and were explained using the results of DFT calculations.
Can carbene decorated [FeFe]-hydrogenase model complexes catalytically produce dihydrogen? An insight from theory
Authors: Borthakur Bitupon , Phukan Ashwini K.
Published: June 2019

Biomimetic [FeFe]-hydrogenase model complexes featuring rotated conformation at one of the iron centres are found to be effective towards dihydrogen production.
Infrared excited Er3+/Yb3+ codoped NaLaMgWO6 phosphors with intense green up-conversion luminescence and excellent temperature sensing performance
Authors: Ran Weiguang , Noh Hyeon Mi , Park Sung Heum , Choi Byung Chun , Kim Jung Hwan , Jeong Jung Hyun , Shi Jinsheng
Published: June 2019

Application of an ultra-sensitive temperature sensor in solid-state lighting and detection of chip temperature.
High relaxation barrier in neodymium furoate-based field-induced SMMs
Authors: Bartolomé E. , Arauzo A. , Luzón J. , Melnic S. , Shova S. , Prodius D. , Nlebedim I. C. , Bartolomé F. , Bartolomé J.
Published: June 2019

Two new neodymium molecular magnets of formula {[Nd(α-fur)3(H2O)2]·DMF}n (1) and {[Nd0.065La0.935(α-fur)3(H2O)2]}n (2), α-fur = C4H3OCOO, have been synthesized and characterized.
Factors affecting spatial and temporal patterns in perfluoroalkyl acid (PFAA) concentrations in migratory aquatic species: a case study of an exploited crustacean
Authors: Taylor Matthew D.
Published: June 2019

Free-ranging prawns showed substantial spatial and temporal variation in PFOS concentrations, most likely driven by behavioural and physiological factors.
Removal of per- and polyfluoroalkyl substances (PFASs) from contaminated groundwater using granular activated carbon: a pilot-scale study with breakthrough modeling
Authors: Liu Charlie J. , Werner David , Bellona Christopher
Published: June 2019

Pilot-scale treatment of PFAS contaminated groundwater with GAC; chain length dependent breakthrough; better PFAS adsorption correlated with more GAC transport pores; breakthrough modeling.
Applications of RAFT polymerization for chemical and enzymatic stabilization of l-asparaginase conjugates with well-defined poly(HPMA)
Authors: Monajati Maryam , Tamaddon AliMohammad , Yousefi Gholamhossein , Abolmaali Samira Sadat , Dinarvand Rassoul
Published: June 2019

HPMA RAFT polymerization and activation with variable linker chemistry for stabilization of l-asparaginase against pH, temperature, freeze–thaw and proteolytic stresses.
The development of unimolecular conjugated polymeric micelles for the highly selective detection and recovery of gold from electronic waste
Authors: Liu Jilin , Yang Ting , Hu Zhiru , Feng Guodong
Published: June 2019

Gold recycling is a sustainable development strategy that will save a large amount of carbon dioxide emissions. In this work, we have developed a conjugated polymer, that can not only detect Au content in e-waste but also extract Au from e-waste.
A novel two-photon fluorescent probe for detecting FA based on a coumarin derivative and its applications in living cells, zebrafish and tissues
Authors: Li Min , Kong Xiuqi , Dong Baoli , Zhang Nan , Song Wenhui , Lu Yaru , Lin Weiying
Published: June 2019

A unique two-photon fluorescent probe,CA, was developed for visualizing FA in living cells, zebrafish and tissues.
Experimental evidence for hypercoordination in triorganotelluronium halides with 2-(Me2NCH2)C6H4 groups
Authors: Beleagă Anca , Denes Eleonora , Silvestru Cristian , Silvestru Anca
Published: June 2019

Triorganotelluronium halides of type [{2-(Me2NCH2)C6H4}nPh3−nTe]+X− (n = 1–3, X = Cl, Br, I) were prepared and structurally characterized both in solution and in the solid state, showing a (C,N)-chelating behavior of the 2-(Me2NCH2)C6H4 groups.
Fluorescence-labeled neopeltolide derivatives for subcellular localization imaging
Authors: Yanagi Shota , Sugai Tomoya , Noguchi Takuma , Kawakami Masato , Sasaki Makoto , Niwa Shinsuke , Sugimoto Asako , Fuwa Haruhiko
Published: June 2019

Fluorescent-labeled neopeltolide derivatives were rationally designed for cell imaging to elucidate their localization in the mitochondria and the endoplasmic reticulum.
Computational elucidation of the binding mechanisms of curcumin analogues as bacterial RecA inhibitors
Authors: Zhou Zi-Yuan , Yuan Jing , Pan Qing , Mo Xiao-Mei , Xie Yong-Li , Yin Feng , Li Zigang , Wong Nai-Kei
Published: June 2019

A mechanistic insights into bacterial RecA protein as a target for curcumin-like compounds offers a theoretical basis for rational design and development of future antibiotic adjuvants.
Highly efficient and flexible photodetector based on MoS2–ZnO heterostructures
Authors: Kang Min-A , Kim Seongjun , Jeon In-Su , Lim Yi Rang , Park Chong-Yun , Song Wooseok , Lee Sun Sook , Lim Jongsun , An Ki-Seok , Myung Sung
Published: June 2019

Two-dimensional transition metal dichalcogenides (TMDs) such as molybdenum disulfide, have recently attracted attention for their applicability as building blocks for fabricating advanced functional materials.
Batch microfabrication and testing of a novel silicon-base miniaturized reference electrode with an ion-exchanging nanochannel array for nitrite determination
Authors: Yin Jiawen , Zhang Wei , Zhang Zan , Jin Han , Gao Wanlei , Jian Jiawen , Jin Qinghui
Published: June 2019

In this paper, a miniaturized Ag/AgCl reference electrode, which can be mass-produced by micro–nano manufacturing technology, was developed and demonstrated to have good stability and a long lifetime.
Structural characterization of phosphoethanolamine-modified lipid A from probiotic Escherichia coli strain Nissle 1917
Authors: Jo Sung-Hyun , Park Han-Gyu , Song Won-Suk , Kim Seong-Min , Kim Eun-Jung , Yang Yung-Hun , Kim Jae-Seok , Kim Byung-Gee , Kim Yun-Gon
Published: June 2019

The probiotic Escherichia coli strain Nissle 1917 is able to colonize the gut more efficiently through lipid A mediated cationic antimicrobial peptide tolerance.
Highly functionalized calix[4]arenesviamulticomponent reactions: synthesis and recognition properties
Authors: Zadmard Reza , Akbarzadeh Ali , Jalali Mohammad Reza
Published: June 2019

Multicomponent reactions (MCRs) include several aspects of green chemistry principles, so it is obvious that chemists in different areas are increasingly interested in providing their product by multicomponent approaches.
Photocatalysis in a multi-capillary assembly microreactor: toward up-scaling the synthesis of 2H-indazoles as drug scaffolds
Authors: Jang Seungwook , Vidyacharan Shinde , Ramanjaneyulu Bandaru T. , Gyak Ki-Won , Kim Dong-Pyo
Published: June 2019

Visible-light-promoted direct arylation of 2H-indazoles using phenyldiazonium salt enabled a single-step and fast synthesis (<1 min) of C3 arylated products in high yields (>65%) in an eosin Y immobilized capillary microreactor.
A triazine-functionalized nanoporous metal–organic framework for the selective adsorption and chromatographic separation of transition metal ions and cationic dyes and white-light emission by Ln3+ ion encapsulation
Authors: Yousaf Afifa , Arif Ali Muhammad , Xu Na , Zhou Jie , Sun Chun-Yi , Wang Xin-Long , Su Zhong-Min
Published: June 2019

A novel MOF1 was designed, which showed the separation of Cu2+ ions and cationic dyes along with white light emission by the encapsulation of Ln3+ ions.
Structural coloration by inkjet-printing of optical microcavities and metasurfaces
Authors: Sardar Samim , Wojcik Pawel , Kang Evan S. H. , Shanker Ravi , Jonsson Magnus P.
Published: June 2019

Flexible, scalable to large areas and low cost fabrication of structurally colored microcavities and plasmonic cavity pixels based on inkjet-printing.
Towards real‐time through‐obstacle imaging based on compressed sensing for sparse objects
Authors: Zhou Tianyi , Shen Fazhong , Meng Qingyang , Li Huan , Xu Kuiwen , Ye Dexin , Huangfu Jiangtao , Dong Shiwei , Denidni Tayeb Ahmed , Ran Lixin
Published: June 2019

Although significant progress has been made in microwave imaging, real‐time imaging, especially for objects behind walls or closed obstacles, remains a technical challenge. In this work, highly efficient imaging for complex‐structured objects surrounded by a closed obstacle was experimentally demonstrated. The imaging equations are derived based on a combination of the inverse‐scattering problem and the concept of compressed sensing. Making use of the spatial sparsity of objects and obstacles, the compressed imaging can be implemented using a time‐division multi‐antenna setup with reduced transmitting antennas. Owing to the spatial compressed sensing applied to the sparse imaging region and objects, the imaging time can be reduced by two orders of magnitude compared with the conventional twofold subspace‐based optimisation method with a comparable imaging quality. Taking advantage of the sparsity of the entire imaging area, objects with larger relative permittivity can also be reconstructed. The proposed method can be potentially used in applications such as security examination through boxes. It also provides a new clue for solving the practicability difficulty faced by existing microwave imaging systems.
Evolution of helium star plus carbon-oxygen white dwarf binary systems and implications for diverse stellar transients and hypervelocity stars
Authors: Neunteufel P. , Yoon S.-C. , Langer N.
Published: June 2019

Context. Helium accretion induced explosions in CO white dwarfs (WDs) are considered promising candidates for a number of observed types of stellar transients, including supernovae (SNe) of Type Ia and Type Iax. However, a clear favorite outcome has not yet emerged.

Aims. We explore the conditions of helium ignition in the WD and the final fates of helium star-WD binaries as functions of their initial orbital periods and component masses.

Methods. We computed 274 model binary systems with the Binary Evolution Code, in which both components are fully resolved. Both stellar and orbital evolution were computed including mass and angular momentum transfer, tides, gravitational wave emission, differential rotation, and internal hydrodynamic and magnetic angular momentum transport. We worked out the parts of the parameter space leading to detonations of the accreted helium layer on the WD, likely resulting in the complete disruption of the WD to deflagrations, where the CO core of the WD may remain intact and where helium ignition in the WD is avoided.

Results. We find that helium detonations are expected only in systems with the shortest initial orbital periods, and for initially massive WDs (MWD ≥ 1.0 M⊙) and lower mass donors (Mdonor ≤ 0.8 M⊙), which have accumulated helium layers mostly exceeding 0.1 M⊙. Upon detonation, these systems would release the donor as a hypervelocity pre-WD runaway star, for which we predict the expected range of kinematic and stellar properties. Systems with more massive donors or initial periods exceeding 1.5 h likely undergo helium deflagrations after accumulating 0.1 − 0.001 M⊙ of helium. Helium ignition in the WD is avoided in systems with helium donor stars below ∼0.6 M⊙, and leads to three distinctly different groups of double WD systems.

Conclusions. The size of the parameter space open to helium detonation corresponds to only about 3% of the galactic SN Ia rate and to 10% of the SN Iax rate, while the predicted large amounts of helium (0.1 M⊙) in progenitors cannot easily be reconciled with observations of archetypical SN Ia. However, the transients emerging from these systems may contribute significantly to massive helium novae, calcium-rich SNe Ib, and, potentially, very close double degenerate systems that may eventually produce either ordinary or peculiar SNe Ia, or, for the smallest considered masses, R Coronae Borealis stars.
Influence of sample preparation on the multi scale structure of sand-clay mixtures
Authors: Yin Kexin , Fauchille Anne-Laure , Othmani Khaoula , Sciarra Giulio , Kotronis Panagiotis , Benoit Yannick , Bertrand Francois , Branchu Samuel
Published: June 2019

This paper focuses on the influence of sample preparation on the multi scale structure of sand-clay mixtures. Three different protocols to mix silica and kaolinite were tested in the laboratory to identify the one providing the most homogeneous microstructure. From the macroscopic to the microscopic scales, optical observation, 3D X-ray tomography, 2D scanning electron microscopy (SEM) and 2D environmental scanning electron microscopy (ESEM) were carried out on wet and dry samples. This paper provides a first insight on the mechanisms of sand clay mixing from the cm to μm scale. Preliminary results demonstrate that the microstructures of the samples prepared by the three procedures have similar macroporosities based on imaging techniques. However, the preparation which consists in mixing the sand firstly, followed by water and clay provides a more homogeneous microstructure with silica grains well-surrounded by an oriented clay layering, probably due to a geometrical effect. Understanding the formation of the oriented clay layering brings microstructural features that will help to better explain the grain displacements and rotations during direct shear tests, the behaviour at the pile sand-clay soil interfaces and to formulate sand clay microstructure models.
Pore size distribution of Brasilia tropical soil in 3 different initial states
Authors: Rodrigues Borges Camilla , de Carvalho Faria Lima Lopes Bruna , Porfírio Cordão Neto Manoel
Published: June 2019

In the last decades there was an evolution in the analysis of the soil structure, most importantly, there was an improvement in the evaluation and in the ways of determining the mentioned structure and how it relates to the hydro-mechanical behaviour of soils. Due to the necessity of understanding the behaviour of tropical soils under different structures (natural, compacted and slurry) this study was developed by means of the Mercury Intrusion Porosimetry (MIP), enabling the analysis of the structural characteristics of these samples. The main objective of this work is to evaluate how the different structures are affected by external loading and how the changes in the pore sizes influences the hydro-mechanical behaviour of the soil in both, saturated and unsaturated conditions. It has been observed that the results regarding the influence of the structure showed a bimodal behaviour. The structural modification of the soil under study, due to the mechanical and / or hydraulic loading, leads to changes in the structure of the macropores and does not affect the micropores. With this, it is noticed that even fixing the parameters related to the microstructure it is possible to make a good adjustment of the macro. This is justified by the fact that the microstructure of all samples are very similar.
Soil microstructural changes induced by suffusion: x-ray computed tomography characterization
Authors: Doan Nguyen Cong , Benahmed Nadia , Andò Edward , Sibille Luc , Philippe Pierre
Published: June 2019

Suffusion is one mechanism of internal erosion, which occurs in gap-graded or broadly graded soils when the fine particles are detached and transported by the seepage flow through the void space formed by the granular soil skeleton. Suffusion is therefore a particle scale mechanism. During this microscale, the initial soil fabric may change due to both fines migration and coarse grains rearrangement, leading to an increase/decrease of global/local porosity and hydraulic conductivity, besides of a probable appearance of heterogeneity, which can, in turn, impact the mechanical behaviour of the eroded soil. In the literature, suffusion test results give only a macroscopic point of view and fail to quantify the effect of suffusion at the scale of the soil's induced heterogeneities. In this paper, x-ray tomography is used to get microscopic observations of soil sample microstructure evolution during a suffusion test. The results reveal that suffusion is not a homogeneous process; the removal of fine particles takes place mainly around the soil sample circumference leading to a higher void ratio at the periphery. Besides, the inter-granular void ratio decreases significantly but almost uniformly throughout the sample owing to the progressive collapse and reorganization of the coarse grains induced by the loss in fines.
Local measurements of axial and radial strains using magnetic encoders in triaxial apparatus
Authors: Witowski Marcin
Published: June 2019

The requirement for implementing local measurements at small strains is well known. Without this type of measurement, it is not possible to accurately identify the soil stiffness characteristics over the entire stiffness degradation curve. The paper presents the results of the use of new sensor based on miniature magnetic encoders for axial and radial deformation measurements in triaxial soil test. Presented results include two types of measurement techniques for radial direction and one for axial deformation.
Influence of sample slenderness and boundary conditions in triaxial test - a review
Authors: Peri Elena , Ibsen Lars Bo , Nordahl Nielsen Benjaminn
Published: June 2019

In the past decades an extensive work was done in order to improve the performance and increase the reliability of triaxial testing. Among the several changes made in order to solve the inaccuracies of the traditional test configuration, two of them are discussed in this paper: the sample slenderness [in other words, the H/D ratio] and the introduction of smooth end platens instead of the rough ones. By using H/D=1 and not the usual H/D=2 ratio, the formation of a single line-rapture and the bulge shape seem prevented. The smooth ends decrease the restrain at the top and bottom of the sample. From a theoretical point of view the effects of these changes are clear, but experimentally, the results coming from various studies are contradictory. The purpose of this paper is to elucidate the previous findings on the topic, including both laboratory and FEM modelling test programs.
Triaxial Simple Shear test: TxSS
Authors: Karray Mourad , Chekired Mohamed
Published: June 2019

This paper presents a combined triaxial simple shear (TxSS) apparatus developed by the Research Institute of Hydro-Québec (IREQ) in collaboration with the soil dynamics and geotechnical engineering group of the Université de Sherbrooke (Québec, Canada). The TxSS system consists of a simple shear apparatus incorporated in a triaxial cell for the measurements of monotonic and dynamic characteristics of soil samples. A general description as well as some applications and advantages of the TxSS systems over the traditional apparatus are presented. The key application of the TxSS is the evaluation of liquefaction potential of soil under regular or irregular excitations. Test results in terms of monotonic and dynamic characteristics obtained using the TxSS device on different cohesive and cohesionless soil samples are presented to illustrate its capabilities. They are successfully compared to those obtained using reliable design charts available in the literature, conventional apparatus and to those from rigorous numerical analyses.
Measuring the fabric evolution of particulate media during load reversals in triaxial tests
Authors: Wiebicke Max , Andò Edward , Herle Ivo , Viggiani Gioacchino
Published: June 2019

The behaviour of granular materials upon load reversal is not yet fully understood. In order to experimentally reveal the microstructure of a specimen subjected to load-unload cycles, a triaxial compression test on lentils is carried out in the x-ray scanner. Before analysing the acquired tomographies, a benchmark analysis is conducted to validate the image analysis tools that are used to extract the fabric from these images. The contact fabric evolves strongly with the shearing in the experiment on lentils. However, only very slight changes of the anisotropy within the cycles are observed.
Aggregation process of kaolinite clay
Authors: Morais Letícia , Cordão-Neto Manoel , Tarantino Alessandro
Published: June 2019

Clay geomaterials pose a great challenge in geotechnical design due to their complex mechanical behaviour. Despite the vast research on clay mechanical behaviour, mechanisms occurring at the particle-scale still remain largely unknown. Particle-to-particle interactions include electro-chemical forces, which can be in turn associated with repulsive/attractive Coulomb interaction and attractive van der Waals force. This work aims to investigate the role of attractive forces (van der Waals and Coulomb) via their control of the process of aggregation (attractive forces tend to form aggregates of clay particles). Dry clay particles were compressed under high stress to reduce particles distances and activate attractive van der Waals and Coulomb forces. Particle size distribution was then measured using laser granulometry to explore aggregation formation. Laser granulometry tests were performed with and without ultrasound and with and without dispersant. Results show that the higher the compressive stress applied to the sample, the bigger is the ‘particle’ size measured by the laser granulometry, which corresponds to formation of aggregation due to attractive forces. Ultrasound appeared to disaggregate the aggregates thus suggesting that van der Waals and Coulomb forces are sensitive to dynamic loading.
Effects of curing stress on the stiffness of a cement-mixed sand
Authors: Filipe Veloso Marques Sérgio , Cesar Consoli Nilo , Festugato Lucas
Published: June 2019

Research into naturally cemented soils (e.g. sandstones) has increased considerably, mostly be-cause of growing interest in offshore oil wells at depths that can, at times, exceed 1000 m. Performing tests directly with on-site soil samples is ideal. However, it's acquisition, transportation and preservation are in-credibly difficult. In order to perform the tests required for this study, the samples were made to simulate the bonding found in naturally cemented soils. Artificially cemented sands were cured under stresses of either 500, 2000 and 4000 kPa, or simply under atmospheric pressure. These specimens were then subjected to drained triaxial compression tests. The results have shown that the curing type has influence over the artifi-cially cemented sand's yield surface and stiffness. The stiffness was vastly superior in specimens cured under higher levels of stress
Influence of structure on the compression behaviour of two very stiff fissured high plasticity Eocene clays
Authors: Sorensen Kenny Kataoka , Rezaei Maryam
Published: June 2019

A series of one-dimensional compression tests have been performed on reconstituted specimens of Søvind Marl. A clear correlation is obtained between the location and the gradient of the intrinsic compression lines and the void ratio at the liquid limit. The found correlation has subsequently been used to normalise the compression curves of 12 one-dimensional compression tests on intact specimens of Søvind Marl and Little Belt Clay obtained from various depths at two sites at Aarhus Harbour. Søvind Marl and Little Belt Clay are both marine sedimentary clays of Eocene age, which can be characterised as very stiff fissured clays with a very high plasticity. From a comparison of the reconstituted and intact compression paths the influence of structure is analysed and discussed in the paper. The majority of intact specimens of Søvind Marl and Little Belt Clay from Aarhus Harbour show similar behaviour; a very stiff recompression path and yielding at high stress level after crossing the intrinsic compression line. The displayed behaviour indicates an insignificant influence of fissuring on the pre-yield behaviour. Post-yield the compression paths indicate a stable structure dominated by fabric rather than metastable interparticle bonds. The paper furthermore highlights the importance of considering the effect of pore water salinity when assessing the influence of structure on the compression behaviour of smectite rich natural marine clays.
Effect of water infiltration on the mechanical behaviour of unsaturated soil
Authors: Rasool Ali Murtaza , Kuwano Jiro
Published: June 2019

Natural slopes and embankments are generally unsaturated in nature with negative pore water pressure adding to the shear strength and hence the stability of the slopes. During the event of rainfall, pore water pressure becomes less negative or even positive as a result the shear strength of soil decreases and failure occur. Therefore, the strength and deformation characteristics for unsaturated soil become important when analysing the stability of these types of slopes. In this study, a triaxial test apparatus was used to study the effect of water infiltration on the mechanical behaviour of unsaturated soil. The test results show that water infiltration decreased with increase in net confining stress and the stress paths were independent of the matric suction, the net confining stress and the shearing conditions for the present experimental study.
A Comparison between Simple Shear and Triaxial Tests for Evaluating the Variations of G and D with Matric Suction
Authors: Fakharian Kazem , Shirkavand Danial , Hejazi Manouchehr
Published: June 2019

Shear modulus (G) and damping ratio (D) are both well known as principal soil dynamic parameters. In the present study, cyclic triaxial and simple shear tests are performed on Firuzkuh silica sand at various shear strain amplitudes using the developed testing devices and peripherals. It is well-understood that degrading curvature of G with shear strain appears in both triaxial and simple shear results. Nevertheless, mean confining stress has dissimilar effects in each of the two tests that does not provide comparable empirical correlations. It is noticed that the variations of G and D with suction stress in triaxial differs from those in simple shear. On the basis of cyclic simple shear results, the increase in suction pressure from zero to the end of transition zone in SWCC leads to increase in G values. In triaxial method, on the other hand, similar increase occurs only up to the inflection point in SWCC, starts reducing afterwards down to a limit value at residual water content. The damping ratio variations with shear strain are generally ascending despite local drops at the strain order of 0.1%, which has appeared in both triaxial and simple shear results.
Cyclic and dynamic behaviour of a Canadian sensitive clay
Authors: d'Onofrio Anna , Chiaradonna Anna , Lanzo Giuseppe , Karray Mourad
Published: June 2019

Clays with higher undisturbed undrained shear strengths than remoulded strengths are considered sensitive. While the stress-strain behaviour of these clays under monotonic loading condition was widely investigated, few data are available of their behaviour under cyclic and dynamic loading conditions. This paper presents the preliminary results of an experimental program on undisturbed samples of a sensitive clay retrieved at Saint Luc de Vincennes (Quebec). In particular, the paper shows the comparison among the modulus reduction curve, G/G0 - γ and the damping ratio variation with shear strain, D - γ measured using different devices, trying to highlight the main factors influencing the observed behaviour , including sample disturbance and storing method. The tests were carried out using one torsional shear and two different cyclic simple shear devices capable of investigating from small to large shear strains. The tests were carried out by three different laboratories at the Université de Sherbrooke, Canada, the University of Naples Federico II and the Sapienza University of Rome, Italy. Oedometric tests also performed by the three different research teams indicate that the clay samples were carefully shipped and stored, and the soil specimens were accurately prepared. Some differences were observed in the G/G0(γ) and D(γ) curves obtained by different tests, some of them ascribed to the intrinsic anisotropy of the investigated clay.
Influence of Overburden on Seismic Compression
Authors: Eric Yee
Published: June 2019

The state of practice for estimating ground settlements from seismic compression is the simplified procedure. This method was developed in the 1980's and gets its name from the relatively easy method of estimating shear strain demands from potential earthquakes at a site. This procedure is generally split into two parts; a procedure that estimates shear strain demands and a volumetric strain material model. The volumetric strain material model essentially correlates shear strain to resultant volumetric strain. The volumetric strain material model used in the simplified procedure is based on a study from the 1970's, where it was observed that cyclic volumetric strain is independent of vertical stress. Laboratory testing was conducted on a variety of soil materials that are able to experience seismic compression. Reconstituted samples were subjected to cyclic loading in an advanced simple shear testing machine known as the Digitally Controlled Simple Shear device. Factors such as density state and fines content were kept constant across soil categories. Test results show volumetric strain behaviour is dependent on vertical stress and the relationship appears to be power rule based.
Shear modulus and damping ratio of a nonplastic silt at large shear strains
Authors: Sezer Alper , Karakan Eyyub , Tanrinian Nazar
Published: June 2019

Site response analyses and solution of dynamic soil-structure interaction problems need determination of variation of shear modulus and damping ratio with shear strain. Since many studies in literature concern evaluation of behavior of sands and silty sands, a series of cyclic triaxial tests were performed to determine the variation of shear modulus and damping ratio of a nonplastic silt with shear strain. Stress controlled cyclic triaxial tests on silt specimens of initial relative densities ranging among 30%, 50% and 70% were performed. Tests were carried out on identical samples under different CSR levels, and the confining pressure was selected as 100 kPa. Variation of shear modulus and damping ratio of silts with cyclic stress ratio amplitude, relative density and number of cycles were investigated. It was understood that soil relative density and cyclic stress ratio amplitude has a significant influence on shear modulus and damping ratio of silts. It was also observed that, as the cyclic stress ratio amplitude is increased, greater shear modulus and lower damping ratio values were obtained.
Thermo-mechanical behaviour of clay-structure interface
Authors: Maghsoodi Soheib , Cuisinier Olivier , Masrouri Farimah
Published: June 2019

The mechanical behaviour of the soil-structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermo-active structures, due to non-isothermal conditions, the interface behaviour becomes more complex. The objective of this study is to investigate the effects of temperature variations on the mechanical behaviour of soils and soil-structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on soil and soil-structure interface in a direct shear device at temperatures of 5, 22 and 60 °C. Kaolin clay was used as proxy for clayey soils. The results showed that, in clay samples the temperature increase, increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The temperature rise had less impact on the shear strength in the case of the clay-structure interface than in the clay samples. The adhesion of the clay-structure interface, is less than the cohesion of the clay samples.
Stiffness of lightly cemented sand under multiaxial loading
Authors: Corte Marina Bellaver , Ibraim Erdin , Festugato Lucas , Diambra Andrea , Cesar Consoli Nilo
Published: June 2019

This paper presents experimental triaxial tests conducted on two lightly cemented sand samples on the set-up conditions of a Hollow Cylinder Torsional Apparatus (HCTA). The laboratory study has been carried out on an angular to sub-angular silica sand reinforced with Portland cement of high early strength. The samples have identical porosity/volumetric cement content ratio, η/Civ, values. The Young's modulus and shear modulus were measured by the application of a series of small unload-reload cycles at different investigation points along the triaxial stress path up to about 50% of the maximum deviatoric stress. At these investigation points, additional series of unload-reload cycles of higher amplitudes were also applied and the stiffness moduli assessed using local instrumentation. While the peak strength seems to be controlled by the density of the sand matrix, as extensive bond cementation damages occur at peak and pre-peak stages, the Young's modulus and shear modulus normalised by the void ratio function show the effect of the cementation ratio with higher values for the sample with higher cementation ratio.
Artificially cemented sand under multiaxial loading
Authors: Festugato Lucas , Bellaver Corte Marina , Ibraim Erdin , Diambra Andrea
Published: June 2019

Distinct improvement techniques can be used when civil engineering structures are to be built on soils that do not present suitable mechanical characteristics. The soil improvement techniques can vary from compaction to chemical and mechanical stabilisation. This work focuses on the specific case of granular soils treated with low amount of cement. The study aims to investigate the behaviour of a cemented sand under multiaxial loading conditions. A series of advanced tests on reconstituted cemented sand were conducted in a Cubical Cell Apparatus (CCA) and exploration of material response including failure limits under different constant stress paths (θ = 0° and θ = 120°) in the octahedral (π) plane were performed. Results showed strength is higher in vertical direction than in horizontal direction.
Utilization of a vinyl based copolymer for improvement of a kaolin type clay
Authors: Bozyigit Irem , Sezer Alper , Erez Batuhan , Kara Burak
Published: June 2019

Geopolymers are obtained by use of alteration of chemical composition and crystal structures of different minerals. Use of geopolymer is an effective and environmental friendly solution in stabilization of clayey soil. The vinyl based copolymer is used as an agent as dust controller, highway soil stabilizer, asphalt admixture, concrete production, etc. In this study, strength of a clay is improved by use of a commercial geopolymer. In this regard, soil was amended with polymer ranging among 0 % to 4 %, by volume of dry soil. Unconfined compression and oedometer tests were carried out to evaluate the effects of temperature, initial water content, compaction energy on strength and compression properties of a clay soil - within an experimental framework. The results revealed that, temperature has a considerable effect on geopolymerization. Besides, under constant moisture content during curing, increasing geopolymer content and curing period causes a slight increase in strength of specimens.
Micro-continuum modelling of injection strategies for microbially induced carbonate precipitation
Authors: Minto James M. , El Mountassir Grainne , Lunn Rebecca J.
Published: June 2019

Microbially induced carbonate precipitation is a promising technique for ground improvement. In order for MICP to progress from a lab-scale process to a commercially viable alternative ground improvement option, a combination of field-trials and field-scale modelling of the process is required. We present the results of a field-scale model in which differing injection strategies are evaluated and find that longer treatment times make more efficient use of reagents, but may come with higher operational costs, and that utilising multiple strains of bacteria with different reaction kinetics and transport properties may improve efficiency.
Timber sheet pile-vegetation model for stream bank retaining structure
Authors: Kamath Abhijith , Gard Wolfgang , Van de Kuilen Jan-Willem
Published: June 2019

Timber sheet piles are widely used to protect canal and stream banks. Quite often, riparian vegetation also grows along these retaining structures. Roots of riparian vegetation mechanically reinforce the soil with their root systems. A timber sheetpile- vegetation model is developed taking into account the mechanical reinforcement of the vegetation roots. The model uses easy to obtain physical parameters, which makes it suitable to have a preliminary estimate of how the forces on the bio engineered structure would evolve.
Multi-scale effects on the hydraulic behaviour of a root-permeated and compacted soil
Authors: Fraccica Alessandro , Romero Enrique , Fourcaud Thierry
Published: June 2019

While roots have been generally proved to be beneficial to soil mechanical behaviour, different and counterposed results have been found when investigating their effects on soil hydraulic response. Roots affect the hydro-mechanical and chemical properties of soils at different scales. In this regard, the paper focuses on studying the macroscopic hydraulic properties of root-permeated and compacted soils considering microstructural features coming from mercury intrusion porosimetry and X-ray micro-tomography. The results are interpreted bearing in mind the influence of the different soil hydraulic states on roots structure and physiology. The analysis of the results shows that roots growing in a compacted soil at low stresses are opening fissures while decreasing micropore volume inside aggregates due to chemical effects. This response has important effects on the hydraulic behaviour of the soil.
Experimental investigation of the mechanical behaviour of soft carbonate rock/grout interfaces for the design of offshore wind turbines
Authors: Stavropoulou Eleni , Dano Christophe , Boulon Marc
Published: June 2019

Since a few years, in France, the development and construction of offshore wind farms in different sites of the country is investigated. The wind turbines will be installed in soft carbonate rock formations (calcarenite, limestone), the mechanical properties of which can vary in a significant way according to the location of the site. Once installed, the bored piles will be sealed with grout in the hosting rock. It is well known that the mechanical behaviour of piles is mainly governed by the behaviour of the interface at the contact between the structure and the hosting rock. The study of the mechanical behaviour of these interfaces, being the weakest points in terms of mechanical resistance, is of great importance for the improvement of the design methods of such infrastructures. The shear response of the rock/grout interface is studied with laboratory experiments in the 3SR lab (Grenoble). The interface's mechanical properties are characterised by a series of shear tests under Constant Normal Stiffness (CNS), these conditions being the most representative of the in-situ conditions. Interface samples of a roughness representative of the in-situ drilling traces, are tested under different levels of applied normal stiffness. The shear response is studied for both monotonic and cyclic shear paths, while all tests are performed under wet conditions. The failure mechanisms are explored, taking into account the contrasting mechanical properties of the two materials composing the interface, as well as, the evolution of the geometrical profile of the interface. The correlation between roughness and the mechanical response of the interface is investigated and the importance of an existing roughness is discussed.
Laboratory investigation of interface shearing in chalk
Authors: Chan Derek L.H. , Buckley Róisín M. , Liu Tingfa , Jardine Richard J.
Published: June 2019

Chalk, a soft fine-grained Cretaceous limestone, is encountered across northern Europe where recent offshore windfarm, oil, gas and onshore developments have called for better foundation design methods, particularly for driven piles whose shaft capacities are controlled by an effective stress Coulomb interface failure criterion. Interface type and roughness is known to affect both interface friction angles, δ′ and the magnitude of dilation required for shaft failure to develop. Site-specific interface ring-shear tests are recommended for offshore pile design in sands and clays to account for driven pile shaft materials, roughnesses and shear displacements. However, few such tests have been reported for chalks and it is also unclear whether δ′ angle changes contribute to the striking axial capacity increases, or set-up, noted over time with piles driven in chalk. This paper describes an interface shear study on low-to-medium density chalk from the St. Nicholas-at-Wade research test site in Kent, UK, where extensive field driven pile studies have been conducted [1, 2]. Direct shear and Bishop ring shear apparatus were employed to investigate the influences of interface material and surface roughness, as well as ageing under constant normal effective stresses (σn'). It is shown that the high relative roughness of the interface compared to the chalk grain size results in the ultimate interface shearing angles falling close to the chalk-chalk shearing resistance angles. The δ′ angles also increased by up to 5° over 38 days of ageing.
Characterisation of contact parameters of sand grains to be used for discrete element modelling
Authors: Balamonica K. , Goh Siang Huat
Published: June 2019

Discrete element method (DEM) is a numerical technique that models the material as a combination of discrete particles which interact with each other through the contacts springs. While modelling soil in finite element method (FEM), approximations are made which considers soil as a continuous material. Hence certain properties such as void ratio which are intrinsic properties of the soil cannot be directly modelled or monitored. FEM also requires the failure criteria to be defined to predict the post elastic behaviour of the soil. DEM overcomes such drawbacks and the particle contacts are the only parameters that has to be defined. In the present work the contact parameters for sand grains are estimated for the purpose of being modelled in DEM, using direct measurement approach. The parameters required for defining the contact springs between the particles are the young's modulus, coefficient of restitution, friction coefficient, Poisson's ratio and density. The estimated parameters from the experiments were used to model the soil behaviour in an oedometer test. The obtained results from the DEM modelling are compared with the experimental results to benchmark the parameters estimated for the sand grains.
Simulation of Realistic Particles with Bullet Physics Engine
Authors: He Hantao , Zheng Junxing , Sun Quan , Li Zhaochao
Published: June 2019

The traditional discrete element method (DEM) uses clumps to approximate realistic particles, which is computationally demanding when simulating many particles. In this paper, the Bullet physics engine is applied as an alternative to simulate realistic particles. Bullet was originally developed for computer games to simulate physical and mechanical processes that occur in the real world to produce realistic game experiences. Physics engines integrate a variety of techniques to simulate complex physical processes in games, such as rigid bodies (e.g., rocks, and soil particles), soft bodies (e.g., clothes), and their interactions. Therefore, physics engines have the capabilities to simulate realistic particles. This paper integrates three-dimensional laser scanner and Bullet to form a realistic particle simulation framework. The soil specimen collapse process is simulated to demonstrate the capability of the proposed framework to simulate realistic particles.
A numerical and experimental study of sand-rubber mixtures subjected to oedometric compression
Authors: Badarayani Pravin , Richard Patrick , Cazacliu Bogdan , Artoni Riccardo , Ibraim Erdin
Published: June 2019

The stockpiling of waste tires at landfill sites has become a nuisance for the society. One of the alternatives could be converting the recycled rubber into powdered form and mixing it with soil to use it as the backfill of the retaining structures. This paper is based on the study of such sand-rubber mixtures. In this work, Discrete Element (DEM) simulations were employed to study the mechanical response of sand-rubber mixtures with respect to a column of grains enclosed within a rigid cylindrical confinement, and subjected to an oedometric compression by the fixed velocity displacement of one of the horizontal walls. Further, experimental analysis was also carried out by using a uniaxial load cell to load the sand-rubber mixtures under compression. Different initial packings of sand-rubber mixture were prepared by varying: (a) the packing volume fraction and (b) the volume fraction of rubber. The mechanical response at small strains was studied for these sand-rubber packings. The mixture behavior was observed to be more sand-dominant or rubber-dominant depending on the rubber fraction and the mixture quality. Moreover, variation in the initial volume fraction of the packing also caused a difference in the load bearing of the packings for a given strain and a given rubber fraction.
Modelling shear strength of compacted soils
Authors: Bulolo Sam , Leong Eng Choon
Published: June 2019

Compacted soils constitute most engineering projects such as earth dams, embankments, pavements, and engineered slopes because of their high shear strength and low compressibility. The shear strength of compacted soils is a key soil parameter in the design of earth structures but it is seldom determined correctly due to their unsaturated state. The shear strength of compacted soils can be better evaluated under the framework of unsaturated soil mechanics. Saturated and unsaturated tests were conducted on compacted specimens using conventional direct shear apparatus under constant water content condition. Tests were conducted at different water contents and net normal stresses. The main objective of this study is to develop a shear strength model for compacted soils. Initial matric suction was measured before the test using the filter paper method. The two-stress state variables together with the extended Mohr-Coulomb failure criterion for unsaturated soils were used to obtain a lower bound model of the shear strength. The model was demonstrated using published data.
A volumetric yield surface for compacted soils based on constant water content testing
Authors: Jayasundara C. , Kodikara J. , Zhou A. N.
Published: June 2019

Unsaturated soils exhibit various complex behaviours compared to saturated soils, such as collapse upon wetting. Therefore, understanding the response of unsaturated soils under general field conditions is essential for the design and construction of safe and economical geotechnical engineering structures. This research is based on the Monash-Peradeniya-Kodikara (MPK) framework proposed by Kodikara [1] for unsaturated compacted soils, which provides a direct link to the traditional compaction loaded curves and constant water content loading experiments. Kodikara [1] named the loaded compaction surface the loading wetting state boundary surface (LWSBS) and validated the model for a combination of loading and wetting stress paths. However, the experimental validation of the yield surface after drying stress paths was not addressed in the original paper. This paper reports the results of drying stress path tests carried out within the specific volume (v),specific moisture ratio (vw) and mean net stress (p) space of the MPK model, and observations suggest that the yield surface is unique after drying stress paths. Mathematical equations for the volumetric behaviour of unsaturated soils are derived using the constant degree of saturation hyperlines derived from constant water content testing, as this enables direct coupling with the soil water retention curve. Finally, the volumetric equations are validated based on the available experimental data.