bluuebunny/crossref_metadata_2025 huggingface dataset:
Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch
Authors: Syvitski Jaia , Waters Colin N. , Day John , Milliman John D. , Summerhayes Colin , Steffen Will , Zalasiewicz Jan , Cearreta Alejandro , Gałuszka Agnieszka , Hajdas Irka , Head Martin J. , Leinfelder Reinhold , McNeill J. R. , Poirier Clément , Rose Neil L. , Shotyk William , Wagreich Michael , Williams Mark
Published: October 2020

Growth in fundamental drivers—energy use, economic productivity and population—can provide quantitative indications of the proposed boundary between the Holocene Epoch and the Anthropocene. Human energy expenditure in the Anthropocene, ~22 zetajoules (ZJ), exceeds that across the prior 11,700 years of the Holocene (~14.6 ZJ), largely through combustion of fossil fuels. The global warming effect during the Anthropocene is more than an order of magnitude greater still. Global human population, their productivity and energy consumption, and most changes impacting the global environment, are highly correlated. This extraordinary outburst of consumption and productivity demonstrates how the Earth System has departed from its Holocene state since ~1950 CE, forcing abrupt physical, chemical and biological changes to the Earth’s stratigraphic record that can be used to justify the proposal for naming a new epoch—the Anthropocene.
Label-free visualization of heterogeneities and defects in metal–organic frameworks using nonlinear optics
Authors: Wolf Mathias , Hirai Kenji , Toyouchi Shuichi , Fron Eduard , Peeters Wannes , De Feyter Steven , Uji-i Hiroshi
Published: October 2020

The potential of nonlinear optical microscopy for the label-free visualization of heterogeneities and defects in metal–organic frameworks is demonstrated.
Visible-light-induced cascade dearomatization cyclization between alkynes and indole-derived bromides: a facile strategy to synthesize spiroindolenines
Authors: Gao Xiaoshuang , Yuan Yao , Xie Xiaomin , Zhang Zhaoguo
Published: October 2020

A visible-light-initiated intermolecular dearomatization cyclization between alkynes and indole-derived bromides provides an efficient way to access a variety of spiroindolenines.
Visible-light-driven Ag/AgCl@In2O3: a ternary photocatalyst for the degradation of tetracycline antibiotics
Authors: Lv Haiqin , Duan Yanyan , Zhou Xin , Liu Guimei , Wang Xin , Wang Yuanhao , Yuan Mingzhe , Meng Qingguo , Wang Chuanyi
Published: October 2020

After coupling with the Ag/AgCl, the obtained Ag/AgCl@In2O3 photocatalyst shows much higher photo-degradation of tetracycline antibiotics than that of In2O3.
Silicon microfabricated reactor for operando XAS/DRIFTS studies of heterogeneous catalytic reactions
Authors: Venezia B. , Cao E. , Matam S. K. , Waldron C. , Cibin G. , Gibson E. K. , Golunski S. , Wells P. P. , Silverwood I. , Catlow C. R. A. , Sankar G. , Gavriilidis A.
Published: October 2020

A novel microreactor for operando XAS and DRIFTS studies of catalytic reactions is reported, exhibiting plug-flow, isothermal behaviour and absence of mass transfer resistances and dead volume, enabling time- and spatially-resolved experiments.
Effect of reduction on the molecular structure and optical and magnetic properties of fluorinated copper(ii) phthalocyanines
Authors: Konarev Dmitri V. , Faraonov Maxim A. , Batov Mikhail S. , Andronov Mikhail G. , Kuzmin Alexey V. , Khasanov Salavat S. , Otsuka Akihiro , Yamochi Hideki , Kitagawa Hiroshi , Lyubovskaya Rimma N.
Published: October 2020

New salts based on reduced fluorinated copper(ii) phthalocyanines were obtained. The effect of reduction on the molecular structure and properties of the  [CuII(FxPc)]n− (x = 8 and 16) species in reduced states (n = 1 and 2) was studied.
Donor–acceptor covalent organic frameworks of nickel(ii) porphyrin for selective and efficient CO2 reduction into CO
Authors: Xu Nanfeng , Diao Yingxue , Qin Xihao , Xu Zhengtao , Ke Hanzhong , Zhu Xunjin
Published: October 2020

Two 2-D donor–acceptor covalent organic frameworks built from porphyrin and diketopyrrolopyrrole are capable of efficiently and selectively reducing CO2 to CO, specifically, without any additional photosensitizers or co-catalysts.
Bulk and interfacial decomposition of formamidinium iodide (HC(NH2)2I) in contact with metal oxide
Authors: Thampy Sampreetha , Zhang Boya , Park Jong-Goo , Hong Ki-Ha , Hsu Julia W. P.
Published: October 2020

Interfacial reaction between formamidinium iodide and metal oxide transport layer triggers degradation and lower the intrinsic stability which is dictated by the oxide, rather than the perovskite.
Probing the versatility of metallo-electro hybrid catalysis: enabling access towards facile C–N bond formation
Authors: Sen Partha Pratim , Dagar Neha , Singh Swati , Roy Vishal Jyoti , Pathania Vishali , Raha Roy Sudipta
Published: October 2020

Metallo-electro catalysis has emerged as sustainable alternate to conventional transition metal methodologies. This review highlights the recent advances for the formation of C–N bonds by merging transition metal catalysis with electrosynthesis.
Simplified computational model for generating biological networks
Authors: Bailey Matthew H. J. , Ormrod Morley David , Wilson Mark
Published: October 2020

We discuss a Monte Carlo method to simulate biological networks and compare to the underlying networks in experimental images.
Mesoporous TiO2 anatase films for enhanced photocatalytic activity under UV and visible light
Authors: Ishchenko Olga M. , Lamblin Guillaume , Guillot Jérôme , Infante Ingrid C. , Guennou Maël , Adjeroud Noureddine , Fechete Ioana , Garin Francois , Turek Philippe , Lenoble Damien
Published: October 2020

Mesoporous TiO2 films with enhanced photocatalytic activity in both UV and visible wavelength ranges were developed through a non-conventional atomic layer deposition (ALD) process at room temperature.
Dual-colour (near-infrared/visible) emitting annexin V for fluorescence imaging of tumour cell apoptosis in vitro and in vivo
Authors: Tsuboi Setsuko , Jin Takashi
Published: October 2020

Indocyanine green labeled recombinant annexin V probes (ICG–EGFP–Annexin V and ICG–mPlum–Annexin V) were synthesized for near-infrared and visible fluorescence imaging of tumor cell apoptosis both in vitro and in vivo.
A naphthalimide-based turn-on fluorescence probe for peroxynitrite detection and imaging in living cells
Authors: Liu Xiling , Gu Fangyuan , Zhou Xinyi , Zhou Wei , Zhang Shuping , Cui Lei , Guo Ting
Published: October 2020

A novel fluorescent probeHCA-OHwas designed for selective detection of peroxynitrite and imaging in HepG2 cells andC. elegans.
A high-precision, template-assisted, anisotropic wet etching method for fabricating perovskite microstructure arrays
Authors: Hu Xue-fang , Lu Chang-gui , Wang Quan , Xu Jing-kun , Cui Yi-ping
Published: October 2020

A template-assisted wet etching method for the preparation of perovskite micro-structure array is proposed. This method has a superiority of flexible graph design, controllable size and high precision.
Syntheses, spectroscopic, redox, and structural properties of homoleptic Iron(III/II) dithione complexes
Authors: Colston Kyle J. , Dille Sara A. , Mogesa Benjamin , Brant Jacilynn , Nemykin Victor N. , Zeller Matthias , Basu Partha
Published: October 2020

Two sets of FeIII/II complexes, synthesized from N,N′-diisopropyl piperazine-2,3-dithione (iPr2Dt0) and N,N′-dimethyl piperazine-2,3-dithione (Me2Dt0) ligands, exhibit electronically asymmetrical ligands with metal–ligand orbital mixing.
Lanthanide contraction effect and white-emitting luminescence in a series of metal–organic frameworks based on 2,5-pyrazinedicarboxylic acid
Authors: Barsukova Marina O. , Cherezova Sofia V. , Sapianik Aleksandr A. , Lundovskaya Olga V. , Samsonenko Denis G. , Fedin Vladimir P.
Published: October 2020

Influence of the lanthanide contraction effect on the formation of a series of new MOFs and their wide colour range luminescence spectra.
Iron-catalyzed α-C–H functionalization of π-bonds: cross-dehydrogenative coupling and mechanistic insights
Authors: Wang Yidong , Zhu Jin , Guo Rui , Lindberg Haley , Wang Yi-Ming
Published: October 2020

[Cp*Fe(CO)2]+ facilitates the α-deprotonation of unsaturated C–C bond for propargylic and allylic C–H functionalization. Mechanistic studies reveal insights into the superior performance of the electron-rich and hindered ligand on iron.
Main group bimetallic partnerships for cooperative catalysis
Authors: Gil-Negrete Jose M. , Hevia Eva
Published: October 2020

Exporting cooperative effects in main group heterobimetallic reagents to catalytic regimes, this Perspective showcases key advances in their applications for hydroelementation, cyclisation, C–C bond formation and polymerization processes.
Hollow Ni0.85Se/Co0.85Se/Co(OH)2hexagonal plates for high-performance hybrid supercapacitors
Authors: Yang Jiaqin , Fan Yuhang , Peng Wenxiu , Li Baofeng , Li Xiaoran , Hu Yuanning , Cui Lifan , Qiao Haimeng , Xu Lirong
Published: October 2020

Hollow Ni0.85Se/Co0.85Se/Co(OH)2hexagonal plates were prepared by controlling the selenylation reaction rate between Ni–Co hydroxide and Se, and the composite showed outstanding cycling stability and satisfactory specific energy and specific power.
Chinese herbs: treasure troves for the discovery of environmentally friendly promoters for methane hydrate formation
Authors: Wang Suying , Zeng Yanxian , Cai Yuanhao , Niu Xiaochun , Zhu Zhengmei , Lei Dongjun , Wang Weixing
Published: October 2020

Chinese herbs can “cure” the sluggish kinetics of methane hydrate formation under static conditions.
Metal cation responsive anionic microgels: behaviour towards biologically relevant divalent and trivalent ions
Authors: Chimisso Vittoria , Conti Simona , Kong Phally , Fodor Csaba , Meier Wolfgang P.
Published: October 2020

Anionic poly(vinylcaprolactam-co-itaconicacid-co-dimethylitaconate) microgels were synthesized via dispersion polymerization and their responsiveness towards cations, namely Mg2+, Sr2+, Cu2+ and Fe3+, was investigated.
Immunotherapy of COVID-19 with poly (ADP-ribose) polymerase inhibitors: starting with nicotinamide
Authors: Badawy Abdulla A.-B.
Published: October 2020

COVID-19 induces a proinflammatory environment that is stronger in patients requiring intensive care. The cytokine components of this environment may determine efficacy or otherwise of glucocorticoid therapy. The immunity modulators, the aryl hydrocarbon receptor (AhR) and the nuclear NAD+-consuming enzyme poly (ADP-ribose) polymerase 1 (PARP 1) may play a critical role in COVID-19 pathophysiology. The AhR is overexpressed in coronaviruses, including COVID-19 and, as it regulates PARP gene expression, the latter is likely to be activated in COVID-19. PARP 1 activation leads to cell death mainly by depletion of NAD+ and adenosine triphosphate (ATP), especially when availability of these energy mediators is compromised. PARP expression is enhanced in other lung conditions: the pneumovirus respiratory syncytial virus (RSV) and chronic obstructive pulmonary disease (COPD). I propose that PARP 1 activation is the terminal point in a sequence of events culminating in patient mortality and should be the focus of COVID-19 immunotherapy. Potent PARP 1 inhibitors are undergoing trials in cancer, but a readily available inhibitor, nicotinamide (NAM), which possesses a highly desirable biochemical and activity profile, merits exploration. It conserves NAD+ and prevents ATP depletion by PARP 1 and Sirtuin 1 (silent mating type information regulation 2 homologue 1) inhibition, enhances NAD+ synthesis, and hence that of NADP+ which is a stronger PARP inhibitor, reverses lung injury caused by ischaemia/reperfusion, inhibits proinflammatory cytokines and is effective against HIV infection. These properties qualify NAM for therapeutic use initially in conjunction with standard clinical care or combined with other agents, and subsequently as an adjunct to stronger PARP 1 inhibitors or other drugs.
Exploring Sentence Diversity at the Boundary of Typical and Impaired Language Abilities
Authors: Hadley Pamela A.
Published: October 2020

Purpose

This review article summarizes programmatic research on sentence diversity in toddlers developing language typically and explores developmental patterns of sentence diversity in toddlers at risk for specific language impairment.

Method

The first half of this review article presents a sentence-focused approach to language assessment and intervention and reviews findings from empirical studies of sentence diversity. In the second half, subject and verb diversity in three simple sentence types are explored in an archival database of toddlers with varying levels of grammatical outcomes at 36 months of age: low average, mild/moderate delay, and severe delay.

Results

Descriptive findings from the archival database replicated previous developmental patterns. All toddlers with low-average language abilities produced diverse simple sentences by 30 months of age and exhibited greater sentence diversity with first-person
I
-subjects before third-person subjects. Third-person subject diversity emerged in a developmental sequence, increasing in one-argument copula contexts and one-argument subject–verb sentences before two-argument subject–verb–object sentences. This developmental pattern held across all three outcome groups. Third-person subjects were least diverse for children with severe grammatical delays and were absent in all sentence contexts for two children with severe delays at 36 months.

Conclusions

Sentence diversity increases gradually and expands in predictable patterns. Understanding these developmental patterns may help identify and treat children who display unexpected difficulty combining different subjects and verbs in flexible ways.

Supplemental Material and Presentation Video

https://doi.org/10.23641/asha.12915320
Causal Pathways for Specific Language Impairment: Lessons From Studies of Twins
Authors: Rice Mabel L.
Published: October 2020

Purpose

This review article summarizes a program of longitudinal investigation of twins' language acquisition with a focus on causal pathways for specific language impairment (SLI) and nonspecific language impairment in children at 4 and 6 years with known history at 2 years.

Method

The context of the overview is established by legacy scientific papers in genetics, language, and SLI. Five recent studies of twins are summarized, from 2 to 16 years of age, with a longitudinal perspective of heritability over multiple speech, language, and cognitive phenotypes.

Results

Replicated moderate-to-high heritability is reported across ages, phenotypes, full population estimates, and estimates for clinical groups. Key outcomes are documentation of a twinning effect of risk for late language acquisition in twins that persists through 6 years of age, greater for monozygotic than dizygotic twins (although zygosity effects disappear at 6 years); heritability is greater for grammar and morphosyntax than other linguistic dimensions, from age 2 years through age 16 years, replicated within twin samples at subsequent age levels and across twin samples at age 16 years.

Conclusion

There is consistent support for legacy models of genetic influences on language acquisition, updated with a more precise growth signaling disruption model supported by twin data, as well as singleton data of children with SLI and nonspecific language impairment.

Presentation Video

https://doi.org/10.23641/asha.13063727
Consensus of multi‐agent system based on novel avoidance function and unequal avoidance strategy
Authors: Zhu Yakun , Li Haoran , Duan Hongjun
Published: October 2020

In practice, the energy of an agent is limited, therefore, saving energy is an important problem in the practical applications of multi‐agent systems. For this problem, the authors firstly proposes a novel collision avoidance function, which have much less energy cost than the normal potential field function. Secondly, to further reduce energy cost, the authors propose an unequal collision avoidance strategy, that is, according to the residual energy of neighbouring agents, high‐energy agent performs collision avoidance, while the low‐energy agent does not. Thirdly, the controller is designed based on the novel collision avoidance function and the unequal collision avoidance strategy. Besides the consensus and collision avoidance can be achieved, the proposed controller can also effectively extend the operation time/range of the whole system. Finally, the simulations verify the effectiveness and superiority of the proposed controller.
Transient analysis of scattering from impedance surfaces using physical optics approximation
Authors: Aktepe Aslihan , Serim Hüseyin Avni , Ülkü Hüseyin Arda
Published: October 2020

Analysis of transient scattering from impedance surfaces using physical optics (PO) approximation is presented. Specifically, a fast relaxed vector fitting scheme is applied to determine a weighted rational function fit to the surface impedance and associated functions in the frequency domain, then inverse Fourier transformed to the time domain in terms of decaying exponential functions. The scattered fields are obtained by convolving the time‐dependent surface impedance (and associated functions) and the PO integral, which is determined via closed‐form expressions obtained using the Radon transform interpretation. The numerical examples that demonstrate the applicability and validity of the proposed method are shown.
A numerical study on the effect of salinity on stability of an unsaturated railway embankment under rainfall
Authors: Kolahdooz Ali , Sadeghi Hamed , Ahmadi Mohammad Mehdi
Published: October 2020

Dispersive soils, as one of the main categories of problematic soils, can be found in some parts of the earth, such as the eastern-south of Iran, nearby the Gulf of Oman. One of the most important factors enhancing the dispersive potential is the existence of dissolved salts in the soil water. The main objective of this study is to explore the influence of water salinity on the instability of a railway embankment due to rainfall infiltration. In order to achieve this goal, the embankment resting on a dispersive stratum is numerically modeled and subjected to transient infiltration flow. The effect of dispersion is simplified through variations in the soil-water retention curve with salinity. The measured water retention curves revealed that by omitting the natural salinity in the soil-water, the retention capability of the soil decreases; therefore, the unsaturated hydraulic conductivity of the soil stratum will significantly decline. According to the extensive decrease in the hydraulic conductivity of the desalinated materials, the rainfall cannot infiltrate in the embankment and the rainfall mostly runs off. However, in the saline embankment, the infiltration decreases the soil suction; and consequently, the factor of safety of the railway embankment decreases.
Volume change behavior of root-permeated soils under partially saturated conditions
Authors: Yildiz Anil , Graf Frank , Springman Sarah M.
Published: October 2020

Vegetation, particularly roots, serves different functions in relation to increased shear strength under saturated and partially saturated conditions. Quantification of mechanical contribution of roots due to their tensile strength, and relationships of various vegetation parameters and plant-induced suction, as well as shear strength, have been widely studied. Although shear strength is directly related to the volume change characteristics of soil, dilative or contractive behaviour of root-permeated soils has not been of significant interest so far. This study investigates how volume change during shearing is related to the hydrological and mechanical characteristics of vegetated soils relevant to slope stability and shear strength of root-permeated soils under partially saturated conditions. Direct shear tests, on specimens planted with a mixture of species from different plant functional groups, were performed with an Inclinable Large-scale Direct Shear Apparatus (ILDSA). Matric suctions were monitored throughout the test with tensiometers. Vertical and horizontal displacement graphs were plotted to investigate the volume change behaviour. Maximum dilatancy angle was found to be positively correlated with plant-induced suction and net normalised stress, both of which were linked to root biomass and the root:shoot ratio. It was found that maximum dilatancy is controlled by matric suction and net normal stress.
Stabilization to prevent soil erosion using vetiver (Chrysopogon zizanioides L.) in slopes: a field case study of selected grounds at Guatemala
Authors: Garzón E. , González-Miranda Flor M. , Reca J. , Sánchez-Soto P.J.
Published: October 2020

The effects of Chrysopogon zizanioides (vetiver) on the hydrophysical properties of soils and infiltration rate have been determined. Thus, it has been examined the stabilization to prevent soil erosion using vetiver in slopes, studying a field case of selected grounds at Guatemala. The particle size analysis of the soil samples showed a predominant sand fraction and a plasticity index of 7.9 %. The results indicated that these soils were fairly acid with worthless salinity and non-swelling. The specific surface area, determined by nitrogen adsorption-desorption analysis, ranged from 11.7 - 15.5 m2 /g and the pore sizes between 17-160 µm, which changed to 20-100 µm, with predominant pore size around 40 µm after cultivation. The characteristics of the soils showed the presence of cohesion (2.05 t/m2) and an internal friction angle Ф = 31.69º. After the plantation, it has been found a decrease in the cohesion and an increase of the internal friction angle. The sowing of vetiver affected the infiltration characteristics of the soil. An analysis using the Kostiakov-Lewis classical model, with a mathematical fitting, has been performed. From these results, it has been deduced that the slope protected using this plant diminished its infiltration rate, being associated to the compaction caused by the plant roots. The present results demonstrated that the plantation of vetiver is effective to stabilize and prevent slopes from the soil erosion caused by severe rainfall events.
Numerical study of the application of capillary barrier systems for prevention of rainfall-induced slope instabilities
Authors: Scarfone Riccardo , Wheeler Simon J. , Smith Colin C.
Published: October 2020

Slope instability is often caused by decreases in suction due to heavy and prolonged rainfall. In this study, the application of capillary barrier systems (CBSs) for suction control and slope stabilization purposes (i.e. reducing the risk of rainfall-induced slope instabilities) is analysed, due to their capacity to limit the percolation of water into the underlying soil. The behaviour of two slopes was studied numerically: a bare slope made of fine-grained soil and the same slope covered by a capillary barrier system. The time evolution of suction in the slopes subjected to realistic atmospheric conditions was studied by performing numerical finite element analyses with Code_Bright. In particular, multi-phase multi-physics thermo-hydraulic analyses were performed, modelling the soil-atmosphere interaction over periods of many years. Suction and degree of saturation distributions obtained from these analyses were then exported to the software LimitState GEO, which was used to perform limit analysis to assess the stability of the slopes. The CBS was able to limit the percolation of water into the slope and was shown to be effective in increasing the minimum values of suction attained in the underlying ground, resulting in improved stability of the slope.
Hydro-mechanical behaviour of a sandy silt from a river embankment
Authors: Butticè Vincenzo , Ferrari Alessio , Gragnano Carmine G. , Gottardi Guido
Published: October 2020

The paper presents the results of an experimental campaign aimed at characterizing the hydro-mechanical behaviour of a sandy silt from a river embankment. Due to continuous river level fluctuations and changing climatic and environmental conditions, flood embankment materials experience frequent variations in degree of saturation and suction values. Such variations strongly impact the earthwork performance both in terms of seepage and stability conditions. For these reasons, a detailed characterization of the material behaviour in unsaturated conditions was carried out. Experiments were designed in order to highlight the response of the involved soil in terms of changes in matric suction and confining stress. All tests were performed on undisturbed samples from the embankment. To cover the suction range, which is expected to be significant for the material and assessed through field monitoring, a combination of several suction-control and suction-measurement techniques was used (e.g. negative water column, axial translation, tensiometers). Obtained results enabled (i) to quantify the evolution of the yield stress with suction, (ii) to assess the collapse upon wetting behaviour, (iii) to get detailed information on the water retention behaviour and (iv) to define the relative permeability of the soil. This extensive characterization work serves as a basis for the analysis of the embankment response following river level variations, the final purpose of the research being to establish a reliable methodology and a feasible procedure for the realistic assessment of the safety margins under transient seepage.
Experimental and Numerical Investigation of the Drying of an Agricultural Soil
Authors: Ralaizafisoloarivony Njaka , Tran Kien , Degré Aurore , Mercatoris Benoît , Léonard Angélique , Toye Dominique , Charlier Robert
Published: October 2020

Due to climate change, soil desiccating became a serious concern in the agricultural area of Belgium. Knowing soil evaporation kinetic can help to elucidate and predict: the soil moisture regime, soil water retention and soil water content. Those parameters are vital for water use efficiency and sustainable agriculture. This research investigated the mechanism of soil evaporation using both laboratory experiment and numerical simulation. Soil samples (Luvisol) were collected from the agricultural field in Gembloux- Belgium, and tested in a small drying chamber. Sensors measured the chamber temperature and humidity, while digital camera monitored the soil surface throughout the experiment. HYPROP device recorded the water change, soil suction, and soil water retention curve. During three evaporation experiments, four periods were observed rather than three as commonly recorded in the theory of drying. The modelling considered thermo-hydro-mechanical framework for predicting the drying process of Luvisol. The model used the finite element code LAGAMINE created at the University of Liege. The software aims at assessing the mechanism of water transport between soil and atmosphere. The results of the simulation showed major domination of Darcean flow during desiccating, while some short vapour diffusion occurred only after the soil surface began to de-saturate.
Exponential Functions for Modelling Hysteresis of Soil-Water Characteristic Curves
Authors: Satyanaga Alfrendo , Kim Jong , Moon Sung-Woo , Wijaya Martin
Published: October 2020

Soil – water characteristic curve (SWCC) is an important property of unsaturated soils that can be used to estimate various parameters to describe unsaturated soil behavior. SWCC is reported to be hysteretic because the water content at a given suction in the wetting process is less than that in the drying process. In order to simulate the hysteretic characteristics of SWCC, many models have been proposed by different researchers. However, majority of the existing models are complex and their parameters are not related to the physical significances of SWCC variables. In this study, the new equations are developed to model drying and wetting SWCC. In addition, some indexes are proposed to estimate the wetting SWCC from drying SWCC. The new equations for SWCCs were evaluated with the laboratory data from published literatures. The results showed that the proposed equations performed well in modelling drying and wetting SWCC. The new equation has less parameters than the existing published equation.
Modelling of unsaturated gas flow by Thebes code: Validation tests
Authors: Abed Ayman , Sołowski Wojciech
Published: October 2020

This paper presents the simulations replicating two well-documented benchmarks on coupled gas-liquid flow in unsaturated soil. The results serve as validation and verification of the formulation of the gas flow in unsaturated geomaterials in the newly developed THMC coupled FEM code Thebes. The paper first discusses the basis of the compositional method and the role of the dry air mass balance equation in the theoretical framework. The fundamental constitutive assumptions related to gas flow, as adopted in the Thebes code, are also discussed in details. Afterwards, the paper discusses simulation of a two-phase infiltration test in unsaturated sand, as well as a one dimensional drainage test. The numerical results of these two examples show that the code is able to capture the main features associated with the gas flow in unsaturated soil. The possible future improvements, both related to the theoretical framework and the numerical implementation, are discussed at the closure of the paper.
Modelling the hydromechanical behaviour of expansive granular mixtures upon hydration
Authors: Darde Benjamin , Tang Anh Minh , Pereira Jean-Michel , Dangla Patrick , Roux Jean-Noël , Talandier Jean , Vu Minh Ngoc
Published: October 2020

Bentonite pellet-powder mixtures are candidate sealing materials in radioactive waste disposal concepts. The mixture is installed in galleries in dry state as a granular material. The material is progressively hydrated by the pore water of the host rock and becomes homogeneous. Before homogenisation, the granular structure controls the material behaviour. In the present work, a modelling approach able to address particular features of pellet-powder mixtures is introduced. Two domains are considered: i) granular, and ii) homogeneous. The material behaviour before homogenisation is studied through Discrete Element Method (DEM) simulations. Constitutive laws for the granular state are proposed from DEM results. The behaviour of the homogenised material is described by a modified Barcelona Basic Model (BBM). Transition from granular to homogeneous states depends on suction and relative volume fractions of pellets and powder. Swelling pressure tests performed in the laboratory are satisfactorily simulated using this approach.
Overview and conceptual constitutive framework for pellet-based buffer materials
Authors: Ghiadistri Giulia M. , Zdravkovic Lidija , Potts David M. , Tsiampousi Aikaterini
Published: October 2020

Buffer materials for nuclear waste disposal applications generally consist of blocks made of highly expansive compacted clay. However, high-density pellets of bentonite are being evaluated as an alternative buffer material for waste isolation. The material response of pellet-based buffers may be quite different from that of compacted buffers, because of the peculiar discontinuous porosity presented. An overview of the literature available on pellet-based buffers is presented and, in particular, two main topics are discussed: firstly, the characteristics of the fabric of the pellets that can be observed through techniques of micro-structural investigation, secondly, the most important behavioural features that can be seen during material testing. Additionally, the constitutive frameworks that have already been developed specifically for pellets are also reviewed. The overall objective of the paper is to highlight the differences between compacted and pellet-based bentonite buffers, in order to propose suitable assumptions to start developing a constitutive model for the latter.
Calibration of a generalized plasticity model for compacted silty sand under constant-suction shearing tests
Authors: García-García Marcos , Patil Ujwalkumar D. , Manzanal Diego , Hoyos Laureano R. , Puppala Anand J. , Pastor Manuel
Published: October 2020

The stress-strain response of compacted silty sand with over-consolidated stress history often exhibit distinct peak stress before reaching the critical stress type of response when subjected to suction-controlled triaxial shearing. Such heavily consolidated soil also tends to simultaneously manifest initial compression which transitions into dilational type volumetric response. Modelling such strain-softening type response, especially emulating the smooth transition from peak to critical state is a challenge. In this paper a previously developed generalized plasticity constitutive model, called MPZ (Modified Pastor-Zienkiewicz) is fine-tuned and calibrated using a set of suction-controlled consolidated drained triaxial tests conducted on compacted silty sand specimens. Firstly, the saturated and unsaturated silty sand characteristics and the experimental test program are briefly introduced. Secondly, the calibration of each component of the constitutive model, namely critical state, dilatancy, peak state, loading direction, water retention curve and bounding function are briefly explained. Furthermore, the material parameters are estimated, model performance is displayed, and finally discussed. Preliminary simulations show that the MPZ model is able to mimic overall suction controlled triaxial test response of compacted silty sand decently well by taking into account the changes in density, pressure and suction. However, the peak states are not accurately modelled for low-high suction levels which needs further modifications in proposed model.
Swelling Curve in Terms of Effective Stress for Expansive Clays
Authors: Baltodano-Goulding Rafael
Published: October 2020

Expansive soils can present an unsaturated state where the soil exhibits volume changes due to both moisture variations that change the state of stresses and moisture variations that interact with its mineralogical characteristics. These special kinds of soils are normally clay type soils that had suffered isomorphous substitution creating a charge imbalance of the clay mineral crystals. This imbalance promotes the trapping of water molecules by the clay particles. It is commonly assumed that a high plasticity index can be an indication of a clay´s high swell potential. However, in arid regions, it is possible to have clays with very high swell potential and low plasticity indexes due primarily to a decrease in the state of effective stress, which will produce expansion of the material. It is common practice to study the swelling characteristics of these soils by performing free-swell tests that can be used for designing removal and replacement backfills or drilled shafts. However, the expansion percentage obtained from this type of test is actually in terms of total stresses and not in terms of effective stress, as it is commonly assumed. Moreover, it is highly dependent on the magnitude of the preload used. This paper presents some efforts made to obtain the swelling part of the curve in terms of effective stresses from the traditional free-swell test. It was hypothesized that the shape of this curve could either have the shape of the rebound curve from a saturated consolidation test or a shape similar to the soil-water characteristic curve.
A physical model for the interaction between unsaturated soils and retaining structures
Authors: Speranza Gianluca , Ferrari Alessio , Laloui Lyesse
Published: October 2020

Temporary and permanent retaining structures interact with soils that are usually in unsaturated conditions. In this work, a 1g-scale physical model is presented to investigate the interactions between retaining walls and unsaturated soils. The physical model is equipped with a water-filled hydraulic cylinder connected to a pressure-volume controller to measure the horizontal component of the later earth thrust and high capacity tensiometers to measure soil matric suction. A system of low-friction linear guideways has been installed at the base of the wall-model. The failure surface is observed through a 3 cm thick glass wall on one side of the container. A series of images are acquired during the tests, and Particle Image Velocimetry (PIV) technique has been used to identify the displacement field. Selected test results on a fine sandy soil are presented, emphasizing the differences in the lateral thrust between dry and partially saturated conditions. The presented results show the impact of the partially saturated condition on both the magnitude of the horizontal component of the lateral earth thrust and the failure mechanism at active state.
Monitoring drying and wetting of a cement bentonite mixture with Electrical Resistivity Tomography
Authors: Musso Guido , Zibisco Antonio , Cosentini Renato Maria , Trischitta Paolo , Della Vecchia Gabriele
Published: October 2020

Cement bentonite slurry cutoff walls are used to encapsulate pollutants within contaminated areas, so avoiding their spreading in the environment. In both temperate and arid climates, at shallow depths, slurry walls are exposed to interaction with the atmosphere and thus to relative humidity values which might induce desaturation and significant shrinkage. This note presents the main results of a study aimed at investigating the impact of drying processes on the integrity and the hydraulic performance of cement bentonite slurry walls. Cement bentonite samples were cured under water for different times (1 months, 2 months and 4 months) and then dried naturally by exposing them to the laboratory environment (T = 21 °C, relative humidity approximately 38%). Once dried, the bottom of the samples was placed in contact with a thin layer of water to induce wetting. The distribution of the electrical conductivity within these samples was evaluated through Electrical Resistivity Tomography measurements, and electrical conductivity maps were converted then into maps of water contents on basis of a phenomenological relationship. The reconstructed water contents compared very well to the measured ones. Drying induced a limited cracking of the samples, which might affect to some extent the hydraulic performance of the barriers.
Preliminary study on the contribution of osmotic effects for the electrical resistivity of sands
Authors: Borges Inês , Gingine Vikas , Cardoso Rafaela
Published: October 2020

Electrical resistivity of soils can be used to evaluate the level of contamination in soils in geophysical prospection tests. The chemical composition of pore fluid also corresponds to a given water potential, named as osmotic suction. Therefore both electrical resistivity and osmotic suction can be related when soil is saturated. This paper investigates their relationship when the soil is not saturated. The osmotic suction and electrical resistivity were measured for uniform grading size samples of sand prepared with different concentrations of an ionic leachate from a real landfield. Both were measured also for the fluid with the different concentrations. Suction was measured for different degrees of saturation using the ionic fluid for the different concentrations. The soil osmotic suction is similar to the osmotic suction of the pore fluid independently from the degree of saturation, and the differences in electrical resistivity in the saturated samples and pore fluid alone as function of osmotic suction are related by a constant. Although pore fluid composition affects electrical resistivity, when evaluating the electrical resistivity considering the degree of saturation one should pay attention to factors that are related with matric suction instead of osmotic suction.
Effect of wetting and drying on meniscus structures in hydrophobic sands
Authors: Karatza Zeynep , Buckman Jim , Medero Gabriela M. , Beckett Christopher T. S.
Published: October 2020

Hydrophobic soils can occur either naturally when particles are coated with plant-derived hydropho-bic organic compounds or if exposed to very high temperatures, or artificially if treated with contaminated water or chemicals in the laboratory. Hydrophobic soils can resist water infiltration, are associated with preferential flow and may lead to increased surface runoffand soil erosion. Traditional understanding of unsaturated hy-drophobic soils suggests that convex water menisci, and so positive water pressures, should form between soil particles, due to contact angles > 90◦. However, experimental results do not support this theory. The objective of this work was to study the changes in meniscus structures in hydrophobic sand specimens, as well as the overall response of the sand to wetting and drying cycles. A very uniform, fine silica sand was mixed with Dimethyldichlorosilane to induce water repellence. Successive images captured in an environmental scanning electron microscope are presented, to examine the response of the sand in two distinct drying and wetting cycles. Preliminary results show that the non-spherical nature of the sand particles prevent or hinder the formation of convex liquid bridges, despite the high contact angles. Rather, water droplets appear to expand only through droplet coalescence, which prevents structures from contracting on drying.
Investigating the contribution of claystone to the swelling pressure of its mixture with bentonite
Authors: Zeng Zhixiong , Cui Yu-Jun , Conil Nathalie , Talandier Jean
Published: October 2020

Compacted MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been considered as a possible sealing/backfilling material in the French deep geological radioactive waste disposal. The swelling pressure of such mixture is an important factor in the design and long-term safety assessment of deep geological repositories. In this study, constant-volume swelling pressure tests were performed on the mixtures with different claystone fractions and dry densities. The test results show that the swelling pressure of the mixtures decreased with the increasing claystone fraction and decreasing dry density. According to the experimental results, the contribution of claystone to the global swelling pressure was further investigated. It was found that the deformation of claystone and its contribution to swelling pressure was highly dependent on the claystone fraction. As the claystone fraction was larger than 30%, the claystone in the mixture swelled, contributing to the global swelling pressure; On the contrary, as the claystone fraction was less than 30%, the swelling of claystone was inhibited by the bentonite and it worked an inert material without any contribution to the swelling pressure.
Changes in mineralogy and microstructure of a lime-treated silty soil during curing time
Authors: YING Zi , Cui Yu-jun , Benahmed Nadia , Duc Myriam
Published: October 2020

Lime treatment is widely applied to improve the workability and long-term durability of soils. In this study, the curing time effect on the mineralogy and microstructure of lime-treated soil was investigated. The soil samples were prepared with 2 % lime and statically compacted at dry (w = 17 %) and wet (w = 20%) sides of optimum. X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) were performed on lime-treated soil at various curing times. The presence of XRD peaks attributed to portlandite even after 150 days curing time indicated that it was not totally converted in cementitious compounds after reaction with silica and alumina from clay minerals. By contrast, no obvious XRD reflections of well-crystallized cementitious compounds were identified. Furthermore, all samples compacted at dry and wet side of optimum exhibited bi-modal pore size distribution, with a decrease of macro-pore frequency with increasing water content. The microstructure changes with increasing curing time did not follow monotonic tendency. On the whole, the quantities of pores less than 0.006 μm and micro-pores increased and the quantity of macro-pores decreased with increasing curing time due to the possible creation of poorly crystallized or amorphous cementitious compounds.
Numerical simulation of a water infiltration test on a proposed backfill material in nuclear waste repositories
Authors: Rawat Abhishek , Dieudonne Anne Catherine , Baille Wiebke , Collin Frederic
Published: October 2020

A water infiltration test was numerically simulated using the finite element method. The modified Barcelona Basic Model and the double-structure water retention model was used for the numerical analysis. A methodology is presented for parameter identification and calibration purpose. The experimental results highlighted the porosity redistribution and hydration-induced heterogeneity along the hydration-path. The simulation results successfully captured the moisture migration in the soil sample. A comparison between the measured and predicted total stress values revealed the influence of interfacial friction between the soil sample and cell wall.
Modelling of oedometer tests on pellet-powder bentonite mixtures to support mock-up test analysis
Authors: Alcantara Arisleidy Mesa , Mokni Nadia , Romero Enrique , Olivella Sebastià
Published: October 2020

Bentonite mixtures of MX-80 (80% of high-density pellets and 20% of bentonite powder on a mass basis) have been recently proposed as a candidate material for sealing deep geological disposals of high-level radioactive waste. A loading/unloading oedometer test at constant water content has been performed on this mixture, which has been modelled using the finite element Code_Bright. The constitutive model used to represent the mechanical response is the Barcelona Expansive Model (BExM), since a multi-modal pore size distribution characterises the pore network of the mixture. During compression at constant water content, an increase in the degree of saturation and a consequent reduction of suction is induced. Consequently, two competing effects occur at different pore-size scales: (a) compression due to mean net stress increase; and (b) expansion on induced suction reduction that mainly affects the micro-porosity level inside aggregates. A sensitivity analysis has been performed to explore these effects, in which the elastic compressibility parameter at the micro-porosity scale for changes in mean effective stress plays an important role.
Low-suction water retention capacity of bentonite at high temperature
Authors: Villar María Victoria , Gutiérrez-Álvarez Carlos , Martín Pedro Luis
Published: October 2020

The study of the hydro-mechanical properties of compacted bentonite is relevant in the context of deep geological radioactive waste repositories, where bentonite will be used as buffer material between the waste canisters and the host rock and will be subjected to high temperatures and hydraulic gradients. This research aimed at determining the water retention curves of bentonite compacted at a repository-significant dry density (1.6 g/cm3) and at high temperatures (up to 100°C). This had been previously undertaken, but below suctions around 10 MPa the accurateness of the curves obtained was very low because of the methods and instruments used to determine them. To overcome this uncertainty, thermocouple psychrometers, which work properly in the low-suction range (below ~6 MPa), were tested. However, calibration showed that their performance was compromised when temperature rose above 60°C. Nevertheless, the results obtained were consistent with previous ones and allowed to confirm the decrease of water retention capacity with temperature. Additionally, it was checked that this decrease was more important for the low suctions.