bluuebunny/crossref_metadata_2025 huggingface dataset:
H2S attenuates endoplasmic reticulum stress in hypoxia-induced pulmonary artery hypertension
Authors: Wu Jianjun , Pan Weili , Wang Chao , Dong Hui , Xing Lei , Hou Jingbo , Fang Shaohong , Li Hulun , Yang Fan , Yu Bo
Published: June 2019

Background: Previous studies have found that hydrogen sulfide (H2S) has multiple functions such as anti-inflammatory, antioxidative in addition to biological effects among the various organs. Exaggerated proliferation and resistance to apoptosis of pulmonary artery smooth muscle cells (PASMCs) is a key component of vascular remodeling. We hypothesized that endogenous bioactive molecular known to suppress endoplasmic reticulum (ER) stress signaling, like H2S, will inhibit the disruption of the ER-mitochondrial unit and prevent/reverse pulmonary arterial hypertension (PAH).

Methods and results: A hypoxic model was established with PASMCs to investigate the possible role of H2S in PAH. Effects of H2S on proliferation of PASMCs were evaluated by CCK-8 and EdU assay treated with or without GYY4137 (donor of H2S). H2S significantly inhibited hypoxia-induced increase in PASMCs proliferation in a dose-dependent manner. H2S by intraperitoneal injection with rats both prevented and reversed chronic hypoxia-induced pulmonary hypertension in rats, decreasing pulmonary vascular resistance, pulmonary artery remodeling and right ventricular hypertrophy, and improving functional capacity without affecting systemic hemodynamic. Exogenous H2S suppressed ER stress indexes in vivo and in vitro, decreased activating transcription factor 6 activation, and inhibited the hypoxia-induced decrease in mitochondrial calcium and mitochondrial function.

Conclusion: H2S effectively inhibits hypoxia-induced increase in cell proliferation, migration, and oxidative stress in PASMCs, and NOX-4 might be the underlying mechanism of PAH. Attenuating ER stress with exogenous H2S may be a novel therapeutic strategy in pulmonary hypertension with high translational potential.
Down-regulation of microRNA-142-3p inhibits the aggressive phenotypes of rheumatoid arthritis fibroblast-like synoviocytes through inhibiting nuclear factor-κB signaling
Authors: Qiang Jianhong , Lv Tingting , Wu Zhenbiao , Yang Xichao
Published: June 2019

The present study aimed to investigate the regulatory roles of miR-142-3p on the aggressive phenotypes of rheumatoid arthritis (RA) human fibroblast-like synoviocytes (RA-HFLSs), and reveal the potential mechanisms relating with nuclear factor-κB (NF-κB) signaling. miR-142-3p expression was detected in RA synovial tissues and RA-HFLSs by quantitative real-time PCR (qRT-PCR) and Northern blot analysis. RA-HFLSs were transfected with miR-142-3p inhibitor and/or treated with 10 µg/l tumor necrosis factor α (TNF-α). The viability, colony formation, apoptosis, migration, invasion, and the levels of interleukin (IL)-6, and matrix metalloproteinase 3 (MMP-3) were detected. The mRNA expressions of B-cell lymphoma-2 (Bcl-2), Bax, Bad, IL-6, and MMP-3 were detected by qRT-PCR. Moreover, the expression of Bcl-2, IL-1 receptor-associated kinase 1 (IRAK1), Toll-like receptor 4 (TLR4), NF-κB p65, and phosphorylated NF-κB p65 (p-NF-κB p65) were detected by Western blot. The interaction between IRAK1 and miR-142-3p was identified by dual luciferase reporter gene assay. MiR-142-3p was up-regulated in RA synovial tissues and RA-HFLSs. TNF-α activated the aggressive phenotypes of RA-HFLSs, including enhanced proliferation, migration, invasion, and inflammation, and inhibited apoptosis. miR-142-3p inhibitor significantly decreased the cell viability, the number of cell clones, the migration rate, the number of invasive cells, the contents and expression of IL-6 and MMP-3, and increased the apoptosis rate and the expressions of Bax and Bad, and decreased Bcl-2 expression of TNF-α-treated RA-HFLSs. MiR-142-3p inhibitor significantly reversed TNF-α-induced up-regulation of IRAK1, TLR4, and p-NF-κB p65 in TNF-α-treated RA-HFLSs. Besides, IRAK1 was a target of miR-142-3p. The down-regulation of miR-142-3p inhibited the aggressive phenotypes of RA-HFLSs through inhibiting NF-κB signaling.
MicroRNA-302d promotes the proliferation of human pluripotent stem cell-derived cardiomyocytes by inhibiting LATS2 in the Hippo pathway
Authors: Xu Fei , Yang Jingcheng , Shang Jun , Lan Feng , Li Miaomiao , Shi Leming , Shen Li , Wang Yongming , Ge Junbo
Published: June 2019

Recent evidence has shown that cardiomyocytes (CMs) can proliferate at a low level after myocardial infarction (MI), but it is insufficient to reestablish heart function. Several microRNAs (miRNAs) have been proven to sufficiently induce rodent CM proliferation. However, whether miRNAs identified in rodents can promote human CM proliferation is unknown due to the poorly conserved functions of miRNAs among species. In the present study, we demonstrate that i) expression of microRNA-302d (miR-302d) decreased significantly during CM differentiation from human pluripotent stem cells (hPSCs) from day 4 to day 18; ii) miR-302d efficiently promoted proliferation of hPSC-derived CMs; iii) miR-302d promoted CM proliferation by targeting LATS2 in the Hippo pathway; and iv) RNA-sequencing analysis revealed that overexpression of miR-302d induced changes in gene expression, which mainly converged on the cell cycle. Our study provides further evidence for the therapeutic potential of miR-302d.
Data fusion based on‐line product quality evaluation of ternary cathode material cyber‐physical systems
Authors: Chen Ning , Dai Jiayang , Tian Shuang , Gui Weihua
Published: June 2019

In the manufacturing process of ternary cathode material, batching, mixing, loading, and sintering procedures play decisive roles in product quality, and data generated by these procedures are collected by the ternary cathode material cyber‐physical system (TCM‐CPS). However, the data of the process are heterogeneous and have different properties, and sampling of key quality variables is difficult. On this basis, on‐line evaluation of product quality is hard. In this study, a data fusion based on‐line product quality evaluation method of TCM‐CPS is proposed. Data features of each procedure are firstly extracted and fused by combining feature indices and kernel principal component analysis. Then, in order to establish the model between the extracted data features and the key quality variables such as particle size and surface‐free lithium content, a semi‐supervised double‐weighted probabilistic principal component regression is proposed. After that, a distance cost index is brought to cluster and grade the two quality variables, which are predicted by the semi‐supervised model. Moreover, the on‐line evaluation of product performance is achieved by setting a rule table in accordance with production experience. Finally, an industrial application verifies the proposed method, of which the effective and accuracy can be acquired from results.
Instantaneous power quality indices detection under frequency deviated environment
Authors: Deng Jianyang , Lam Chi‐Seng , Wong Man‐Chung , Sin Sai‐Weng , Martins Rui Paulo
Published: June 2019

The proliferation of massive non‐linear loads, large motor loadings, renewable energy generation systems etc. creates many problems to the electrical power systems, such as harmonics, oscillations, which lead to the unnecessary economic cost. It is critical to implement satisfying continuous monitoring of the power quality (PQ) over the power systems. Previous works have proposed many PQ detection methodologies with promising accuracy and performance, but as more and more renewable energy is integrated into the power systems, a new challenge of frequency deviation has been raised. The accuracy of the conventional methodologies will be degraded under the frequency deviated environment, then the authors proposed in this study an instantaneous PQ indices (PQIs) detection methodology based on adaptive data resampling technique to improve the accuracy of PQIs detection within a frequency deviated environment. Finally, they validated the effectiveness of the proposal, which obtains better accuracy and performance under a frequency deviated environment with less readjustment, through simulation and measurement. Furthermore, the proposed methodology satisfies the definitions and recommendations of the IEEE Std 1459 and IEEE Std 519.
Study of CS, SiO, and SiS abundances in carbon star envelopes: assessing their role as gas-phase precursors of dust
Authors: Massalkhi S. , Agúndez M. , Cernicharo J.
Published: June 2019

Aims. We aim to determine the abundances of CS, SiO, and SiS in a large sample of carbon star envelopes covering a wide range of mass loss rates to investigate the potential role that these molecules could play in the formation of dust in the surroundings of the central AGB star.

Methods. We surveyed a sample of 25 carbon-rich AGB stars in the λ 2 mm band, more concretely in the J = 3−2 line of CS and SiO, and in the J = 7−6 and J = 8−7 lines of SiS, using the IRAM 30 m telescope. We performed excitation and radiative transfer calculations based on the large velocity gradient (LVG) method to model the observed lines of the molecules and to derive their fractional abundances in the observed envelopes. We also assessed the effect of infrared pumping in the excitation of the molecules.

Results. We detected CS in all 25 targeted envelopes, SiO in 24 of them, and SiS in 17 sources. Remarkably, SiS is not detected in any envelope with a mass loss rate below 10−6 M⊙ yr−1 while it is detected in all envelopes with mass loss rates above that threshold. We found that CS and SiS have similar abundances in carbon star envelopes, while SiO is present with a lower abundance. We also found a strong correlation in which the denser the envelope, the less abundant are CS and SiO. The trend is however only tentatively seen for SiS in the range of high mass loss rates. Furthermore, we found a relation in which the integrated flux of the MgS dust feature at 30 μm increases as the fractional abundance of CS decreases.

Conclusions. The decline in the fractional abundance of CS with increasing density could be due to gas-phase chemistry in the inner envelope or to adsorption onto dust grains. The latter possibility is favored by a correlation between the CS fractional abundance and the 30 μm feature, which suggests that CS is efficiently incorporated onto MgS dust around C-rich AGB stars. In the case of SiO, the observed abundance depletion with increasing density is most likely caused by an efficient incorporation onto dust grains. We conclude that CS, SiO (very likely), and SiS (tentatively) are good candidates to act as gas-phase precursors of dust in C-rich AGB envelopes.
Using the infrared iron lines to probe solar subsurface convection
Authors: Milić I. , Smitha H. N. , Lagg A.
Published: June 2019

Context. Studying the properties of solar convection using high-resolution spectropolarimetry began in the early 1990s with the focus on observations in the visible wavelength regions. Its extension to the infrared (IR) remains largely unexplored.

Aims. The IR iron lines around 15 600 Å, most commonly known for their high magnetic sensitivity, also have a non-zero response to line-of-sight (LOS) velocity below log(τ) = 0.0. In this paper we explore the possibility of using these lines to measure subsurface convective velocities.

Methods. By assuming a snapshot of a three-dimensional magnetohydrodynamic simulation to represent the quiet Sun, we investigate how well the iron IR lines can reproduce the LOS velocity in the cube and to what depth. We use the recently developed spectropolarimetric inversion code SNAPI and discuss the optimal node placements for the retrieval of reliable results from these spectral lines.

Results. We find that the IR iron lines can measure the convective velocities down to log(τ) = 0.5, below the photosphere, not only at the original resolution of the cube, but also when degraded with a reasonable spectral and spatial PSF and stray light. Instead, the commonly used Fe I 6300 Å line pair performs significantly worse.

Conclusions. Our investigation reveals that the IR iron lines can probe the subsurface convection in the solar photosphere. This paper is a first step towards exploiting this diagnostic potential.
Solutions to the Hamilton-Jacobi equation for Bolza problems with discontinuous time dependent data
Authors: Bernis Julien , Bettiol Piernicola
Published: June 2019

We consider a class of optimal control problems in which the cost to minimize comprises both a final cost and an integral term, and the data can be discontinuous with respect to the time variable in the following sense: they are continuous w.r.t. t on a set of full measure and have everywhere left and right limits. For this class of Bolza problems, employing techniques coming from viability theory, we give characterizations of the value function as the unique generalized solution to the corresponding Hamilton-Jacobi equation in the class of lower semicontinuous functions: if the final cost term is extended valued, the generalized solution to the Hamilton-Jacobi equation involves the concepts of lower Dini derivative and the proximal normal vectors; if the final cost term is a locally bounded lower semicontinuous function, then we can show that this has an equivalent characterization in a viscosity sense.
Sand grains versus tiny glass granules - comparative study on stress-deformation characteristics
Authors: Leśniewska Danuta , Radosz Iwona , Pietrzak Magdalena
Published: June 2019

Glass granules and grains of crushed glass usually replace sand if photo-elastic observation of load-transmitting ‘force chains’ is planned. Still an open question exists however, how well glass granules can represent real sand grains. This paper in its first part compares simple uniaxial crushing tests on glass grains (both granules and crushed glass) and on coarse sand grains (micro-scale). Some basic geometrical characteristics of glass and sand grains are discussed, then the measurement techniques are presented and the results of crushing tests demonstrated. The second part of the paper contains the results of ‘macro-scale’ loading tests on big granular samples, made of ~106 glass or sand grains. The deformation characteristics of these samples differ significantly.
An appraisal of end conditions in advanced monotonic and cyclic triaxial testing on a range of geomaterials
Authors: Vinck Ken , Liu Tingfa , Ushev Emil , Jardine Richard J.
Published: June 2019

Compressing samples between rigid platens, as in triaxial testing, induce non-uniform specimen stress, strain and pore water distributions. Although well recognised historically, the effects of such platen restraints are often disregarded or overlooked when performing or interpreting monotonic and cyclic experiments. This paper presents an updated appraisal of end conditions based on laboratory experiments run on sand, glacial till, intact and puttified chalk as part of offshore piling research projects. Monotonic and cyclic triaxial tests are reported that incorporated local strain and pore pressure sensors and a range of platen configurations. New insights are reported regarding the small-to-large behaviour and undrained cyclic pore water pressure measurement.
The effect of clay water content in the Jet Erosion Test
Authors: Beber Raniero , Tarantino Alessandro , Pedrotti Matteo , Lunn Rebecca
Published: June 2019

The understanding of the onset of breaching induced by surface erosion is fundamental to enable definition of the level of protection afforded by embankments and provision of standards for the design of new structures and the upgrading of existing ones. Compacted embankment materials are generally partially saturated due to seasonal variation in the water content. At the onset of the overflow process embankments undergo to a wetting process due to the changes at the outer surface boundary conditions (i.e. overflow). Erosion behaviour is known to be a counterbalance between gravity forces and shear erosion forces. However, as the particle size decreases (i.e. clayey soils), gravitational forces become negligible and electrochemical interaction between particles play a dominant role. Clay microstructure (e.g. particle configuration and inter-particle forces) changes with the hydro-mechanical stresses history. Thus, it is necessary to consider the microstructural changes in particle configuration to understand the influence of microstructure on the macroscopic behaviour of clay during erosion. Upon wetting, clay have a swelling/collapse behaviour. This research presents experimental results on erosion of clay samples compacted at the same initial dry density but with different compaction water content. The influence of different wetting times on erosion is also investigated. We show that for a given as-compacted water content, the longer the wetting stage, and hence the higher the sample water content, the more erodible the samples. Additionally, for samples compacted at the same dry density, the ones compacted on the dry side of optimum are more erodible than samples compacted at the optimum water content, despite the lower water content at formation. We hypothesise that this may be due to the formation of a different initial microstructure in sample on the dry side of optimum (i.e. bi-modal pore size distribution). Our results contribute to the fundamental understanding of time-dependent mechanisms that influence erosion of clay embankments during overflow and, hence, to embankment failure. In addition, these tests show how basic concepts of unsaturated soil mechanics can serve as a guide to ‘design’ the compaction conditions of embankment material.
The effect of aggregations on bimodal kaolinite soils
Authors: de Oliveira Kühn Vinícius , Porfírio Cordão Neto Manoel , de Carvalho Faria Lima Lopes Bruna
Published: June 2019

Residual bimodal soils present great complexity of hydraulic and mechanical behaviour, due to the presence of aggregations, mineralogy and complex structures. These soils often present a clear bimodality with a wide difference between the size of intra-aggregate and inter-aggregate pores, of 2 to 3 orders of magnitudes. The objective of this work is to produce a soil with bimodal characteristics using Kaolin Clay, in order to eliminate possible mineralogical, particle size and structural variables, since the clay mineral present in this material is mainly Kaolinite. Analyses of the effect of stable aggregations on soil structural behaviour were carried out by means of soil water retention curve (SWRC). For this, a new methodology was developed for the production of stable aggregations, which were used to compose new bimodal soils. Then, a series of comparisons between the SWRC of the soil with and without aggregation were carried out. Results showed that the presence of aggregations had a direct impact on soil plasticity, particle size classification and compaction curve.
Correlation between shear wave velocity and effective confining pressure using cyclic triaxial testing apparatus
Authors: Liu Guojun , Yasufuku Noriyuki , Ishikura Ryohei , Liu Qiang
Published: June 2019

The 2016 Kumamoto earthquakes struck Kumamoto and Ōita regions and caused several devastating liquefaction induced damages. The primary damage was due to the extreme ground shaking of the foreshock and main shock sequence. Therefore, it is essential to develop a quick reliable approach with a high accuracy to assess the ground situation after foreshock or several shocks. Velocity of small shear wave (Vs) was widely used for evaluating the potential liquefaction. This study investigates the possibility of using Vs as a new indicator of the stress state in the soil after earthquake and evaluation of post liquefaction resistance of soil. Cyclic tri-axial apparatus equipped with bender elements were used to conduct two consecutives liquefaction tests on sandy soil. The Vs measured by bender elements was discussed on the relationship with effective stress during the liquefying processes. The results showed that for the sandy soils, a) Vs could not clearly reflect the significant reduction in resistance at re-liquefaction stages by directly comparing the Vs at the end of consolidation between first and stages, b) The shear wave velocity is significantly affected by effective confining pressure c) the shear wave velocity of 190 m/s was at confining pressure of 100 kPa. The shear wave velocity reaches to after 100 m/s after consolidations and re-consolidations. The shear wave velocity was found to reduce to 100 m/s when the effective confining stress reaches to 0 and to around 25 m/s when the double amplitude reaches to 5%; d) the velocity and effective stress decreases with a similar rate in liquefying process.
Genuine and false pre-consolidation and yield pressures
Authors: Wesley Laurence D
Published: June 2019

“It remains a mystery why the international profession still uses the awkward e-log p plots, and the incomplete and useless coefficient Cc which is not even determined from the measured data, but from a constructed line outside the measurements”. These are the words of Nilmar Janbu (1998). This paper does not solve the mystery; what it does is highlight the issue behind the mystery in the hope that the profession will face up to the defects of the log scale. An examination is made of oedometer test results when plotted to both scales. Examples are given for sedimentary and residual clays, and sands. It is shown that the e-logp plot routinely produces graphs from which pre-consolidation pressures or yield pressures can be determined. However, when plotted using an arithmetic (linear) scale, this apparent pre-consolidation or yield pressure is found, in most cases, to disappear. It is a false value created by the way the data are plotted. The paper does not deny that pre-consolidation or yield pressures exist in many soils; it gives examples for each of the soil types listed above. It is recommended that the term “yield pressure” be used in preference to “pre-consolidation pressure”, and that only the use of a linear scale will reveal whether such a pressure exists.
Critical State Lines of Portuguese liquefiable sands
Authors: Ramos Catarina , Ferreira Cristiana , Molina-Gómez Fausto , Viana da Fonseca António
Published: June 2019

The Critical State framework has been used to describe the behaviour of sands and study the liquefaction susceptibility of these soils when sheared in static and cyclic conditions. The ocean coast and some fluvial basins of Portugal are characterised by the presence of sandy deposits that, combined with a moderate to high seismic activity, creates the conditions for moderate to high liquefaction susceptibility. The aim of this work is to study and compare five Portuguese liquefiable alluvial sands, collected in the centre-south of the continental territory. The experimental programme included a complete physical identification of the five materials and a series of triaxial tests in drained conditions. The specimens were prepared at a high initial void ratio (loose), using the moist-tamping technique with an appropriate initial water content, reaching void ratios close or slightly higher than emax. The specimens were fully saturated, isotropically consolidated and statically sheared at constant strain rate until reaching the critical state. Shear wave velocities after consolidation were measured using bender elements. The critical state and small-strain stiffness parameters are discussed and compared, evidencing the differences between these soils. Relationships between some of these parameters and physical characteristics are obtained.
Soil Particle Movement and Shear Band Development during Plane Strain Compression
Authors: Hwang Junggeun , Ling Hoe I.
Published: June 2019

Most geotechnical structures failed by formation and development of shear bands in soils. Thus, shear deformation and shear bands development evaluation are necessary to understand shear failure mechanism. During shearing, deformation behaviour analysis for soil particles within entire soil specimen are evaluated to understand the soil behaviour and shear strength characteristics. In this paper, a series of plane strain compression tests using Nevada sand and Ottawa sand were conducted to identify the shear strain and shear failure mechanism. With the results of plane strain compression tests, image analyses using Particle Image Velocimetry (PIV) were carried out in order to measure the change in position of soil particles and shear bands development. Deformation vectors and contours were constructed to see the entire deformation mechanism in the soil specimen. During shearing, shear band was identified after peak stress and most visually distinctive at residual state. However, shear band started to develop invisibly immediately after starting loading and this invisible development was able to be observed by horizontal and vertical movement analyses of PIV. Soil particles moved actively in horizontal and vertical direction to generate shear band in the beginning of shearing. After development of shear band, soil particles moved along the shear band.
Prediction of unsaturated shear strength from microstructurally based effective stress
Authors: Mpawenayo Régis , Gerard Pierre
Published: June 2019

This work aims at investigating the adequacy of microstructurally based effective stress to predict the shear strength of unsaturated soils over a wide range of suction. For that purpose, shear strength data are acquired on a silty clay soil through two types of unsaturated triaxial tests: suction controlled triaxial tests and unconsolidated triaxial tests at constant water content. The microstructure of the soil is determined with Mercury Intrusion Porosimetry and is directly used in different expressions of microstructurally based effective stresses available in the literature. The large range of suction tested allows to determine the most consistent expression of the effective stress to reproduce the experimental observations.
Behaviour of a loose silty sand under static and cyclic loading conditions
Authors: LeBoeuf Denis
Published: June 2019

In recent years, considerable progress have been made in the study of liquefaction and flow failures with the introduction of the notion of steady-state of deformation and “collapse” envelope. These concepts are increasingly used in seismic stability analysis of slopes or embankments. However, as most of these studies were carried out on clean sands in the triaxial apparatus, one may question the general applicability of these results to practical conditions as several factors such as anisotropy, fines content, undrained strength anisotropy, boundary deformation conditions, stress history, etc. may play an important role. In this paper, the behaviour of the same soil, a loose silty sand, is compared for different loading and testing conditions: drained and undrained triaxial compression tests, drained and constant volume monotonic and cyclic direct simple shear (DSS) tests. Results allow to identify similarities and differences, in terms of undrained initial and steady-state shear strength and modes of undrained failure between triaxial and DSS test conditions and show that liquefaction in DSS cyclic tests is an instability triggered by shear failure developing once the friction corresponding to the characteristic envelope, as identified in the monotonic test, has been mobilized.
Cyclic resistance of a decomposed granite
Authors: Hadsari Vienti , Russell Adrian R.
Published: June 2019

An important issue surrounding the identification of liquefaction susceptibility using laboratory testing is how well the soil sample being tested represents the soil in the field. Undisturbed samples are difficult and costly to obtain, while reconstituted soil samples must have a structure and fabric that represents in situ conditions as closely as possible. Recent laboratory tests on sand samples revealed that liquefaction resistance is strongly affected by the sample preparation technique, as different techniques result in different fabrics and structures. The same may be true for silty sand samples, although they have not been given the same research attention. Thus, this paper presents cyclic triaxial test results on non-plastic silty sand samples (a decomposed granite) and determines the number of cycles required to cause liquefaction, considering different failure criterion as well as different confining pressures, cyclic strength ratios and sample preparation techniques. The techniques include dry and slurry deposition. The experimental results show that the preparation technique does not have a significant influence on cyclic resistance.
Vulnerability of volcanic loose soils having cementation and crushable particles
Authors: Sato Itsuki , Kuwano Reiko
Published: June 2019

In Japan, a multitude of slope disasters occur annually, resulting in often severe loss of human life. On occasion, disasters that occur at very gentle slopes and disasters that flow long distance, associated with destructive energy, are observed. In such cases, the trigger layer often consists of volcanic soils with extremely high void ratios and external triggers, including earthquake or heavy rainfall, increase the risk of slope disasters. These volcanic soils are often characterised by an extremely loose structure and are either retained mainly by weak cementation or are composed of crushable particles having intra voids. Although the cause of destructive long-distance flow has been explained by liquefaction, there are some observed disasters in which the trigger layer was not fully saturated, i.e. liquefaction should not be considered as a major cause. Focusing on the fact that long-distance flow or gentle slope flow, disasters are triggered by volcanic soil layers of extremely loose structure, artificial loose soil samples were prepared in the laboratory. These samples were prepared with cementation between particles and with crushable particles. In this study, deformation and strength characteristics of the extremely loose soils were investigated by conducting CD triaxial tests. It is revealed that such extremely loose soils can be vulnerable after the weakly cemented structure collapses as a result of external factors such as earthquakes.
Weathering-induced deformation of crushed weak rocks and its countermeasure
Authors: Putra Andius D. , Takahashi Masaya , Kikumoto Mamoru
Published: June 2019

Geotechnical issues such as differential settlements have been reported usually in embankments made of materials derived from weak rocks such as mudstones, siltstones, and shales. The primary cause of the issue is a gradual weakening due to weathering. Crushed weak rocks tend to turn into smaller particles under repeated wetting and drying processes. This phenomenon is a mechanical-hydraulic process known as “slaking”. The present paper discusses the deformation of crushed weak rocks due to slaking and its countermeasure. We performed a series of one-dimensional slaking tests on several weak rocks. We first performed one-dimensional compression tests on dried samples, and applied wetting and drying cycles to the samples while keeping the compression stress constant. The test results revealed that particle size distribution of the samples was broadened due to cyclic wetting and drying processes and that significant compression was exhibited. Moreover, we explored possible countermeasures for reducing the slaking-induced deformation and revealed that compacting the soil to a denser state is the most effective way in reducing the slaking-induced deformation of the crushed mudstone.
Effects of cement and foam addition on chemo-mechanical behaviour of lightweight cemented soil (LWCS)
Authors: De Sarno Domenico , Vitale Enza , Deneele Dimitri , Nicotera Marco Valerio , Papa Raffaele , Russo Giacomo , Urciuoli Gianfranco
Published: June 2019

One of the main problems encountered in civil engineering is the management of large amounts of excavated soil, especially when the mechanical properties of this soil are not suitable for its reuse as a construction material. However, the excavated soil could represent a resource if appropriately improved. A suitable solution is the addition of cement and foam to produce lightweight cemented soils (LWCS). In this paper, an insight into the influence of foam on chemo-mineralogical and microstructural features of soil-cement-water system is presented. Time dependent mineralogical and microstructural changes have been monitored by means of X-Ray Diffraction, Thermo-gravimetric analysis and Mercury Intrusion Porosimetry. The present study shows that addition of foam does not alter the chemo-physical evolution of the soil-cement-water system. Large voids are present in the samples as footprint of air bubbles upon mixing, thus increasing porosity. Macroscopic behaviour of treated samples has been investigated by direct shear and oedometric tests. Chemo-physical evolution induced by cement addition is the major responsible for mechanical improvement showed by treated samples. Porosity of samples induced by foam addition plays a key role in the mechanical response of LWCS, inducing a transition of stress-strain behaviour from brittle and dilative to ductile and contractive as a function of increasing foam content.
Preliminary observations of the shear behaviour of fungal treated soil
Authors: Salifu Emmanuel , El Mountassir Gráinne
Published: June 2019

This paper presents results of an investigation into an entirely novel technique for ground improvement involving the use of fungal hyphae. Fungal hyphae (long filamentous branches) are known to contribute to soil aggregation and soil hydrophobicity, and are hypothesised to also influence the hydro-mechanical behaviour of soil. We present here preliminary observations of the mechanical behaviour of sands treated with the fungal species Pleurotus ostreatus (P. ostreatus). Direct shear tests were carried out on sand containing different percentages of organic substrate (the nutrient source for fungal growth) and treated with P. ostreatus. The stress-strain behaviour of fungal treated and untreated soil was investigated. Results show that irrespective of the percentage of organic matter, fungal treated specimens tended to show a loss in the peak behaviour characteristic of the untreated control specimens and an associated transition towards a more contractive volumetric response. The limited experiments conducted to date appear to indicate that the main factor responsible for the differences in behaviour between treated and untreated specimens is due to lubrication of the grains by the fungal hyphae and exudates. Further investigation is required to fully elucidate the mechanisms influencing the mechanical behaviour of fungal-treated soils.
Behaviour of fibre-reinforced cemented sand under flexural tensile stress
Authors: de Paula Thaís Martins , Consoli Nilo Cesar , Festugato Lucas , Favretto Filipe , Daronco João Victor Linch
Published: June 2019

In soil improvement, the insertion of cement to the soil matrix provides an increase in strength and rigidity of the material, whereas fibre addition provides an increase in ductility, reducing post-peak loss in strength. This research aims to experimentally analyse the mechanical behaviour of unreinforced and fibre-reinforced cemented sands under flexural tensile monotonic loading conditions. In order to do so, an experimental program was planned using silty sand (Arenito Botucatu), early strength Portland cement – CPIII, and polypropylene fibres 24 mm long and 0.023 mm thick. Three different dry unit weights (γd) (18, 19 and 19.7 kN/m3), three cement contents (3, 5 and 7%), and two fibre contents (0 and 0.5%) were chosen. Analysing the results, an increase in cement content generates an increase in flexural strength (qf) for all concentrations and the increase in γd generated smaller qf gains, especially for lower cement contents. The addition of fibres generated a qf increase for lower γd but at higher γd there was a reduction in the influence of fibre addition on strength gain. The reduction can be attributed to an entanglement of the fibres in higher compaction strengths, disrupting the formation of cementitious bonds. However, based on a qualitative assessment, there was a noticeable reduction in post-peak strength loss due to fibre insertion. The parameter porosity/volumetric cement content (η/Civ0.28) was considered suitable to predict the qf mechanical behaviour of the studied composite.
Root-reinforced sand: kinematic response of the soil
Authors: Anselmucci Floriana , Andó Edward , Sibille Luc , Lenoir Nicolas , Peyroux Robert , Arson Chloé , Viggiani Gioacchino , Bengough A. Glyn
Published: June 2019

The influence of the soil on the growth of a root system has been largely investigated. By contrast, the aim of this work is to go deep into the details of how the soil may be influenced by the root system. In particular, the root growth process and its potential to improve the soil strength is explored. Even though roots can be seen as fiber-like reinforcements, their growth changes the soil microstructure. Consequently, one of the objectives is to understand how the water content and the soil displacement fields evolve when an inclusion expands radially and axially. In particular, an investigation was carried on to characterise the deformation of the solid phase of the soil, due to the root growth. A series of in-vivo x-ray tomographies was acquired with Maize seeds growing roots into a coarse Hostun HN1.5-2 sand. Digital Image Correlation is used to calculate the soil 3D displacement fields around the growing plant roots.
Preliminary Evaluation of Concrete-Rock Interface Behavior Under the Action of Freeze-Thaw Cycles
Authors: Ho Chun-Hsing , Chivens Kurtis , Floyd Spencer , Barger Joshua , Avina Kenya , Geier Mitchell
Published: June 2019

The most common source of failure for tunnellining occurs at the excavated surface due to a high frequency of freeze-thaw cycles and cold weather that significantly drop the strength of the interface between the rock and the concrete. A preliminary experiment was conducted to confront the problems associated with cold weather effect on concrete and the adhering connection between the concrete and the excavated rock surface. A series of composite specimens made of sandstone rocks and concrete with the three types of surfaces (smooth, semi-rough, and rough) were prepared in the Materials Laboratory of Northern Arizona University. All specimens were undertaken up to 180 Freeze-thaw cycles using an ASTM C666 apparatus with modifications on molds and dimensions of specimens. Tensile splitting tests of the interface between concrete and three types of rock surfaces were performed with respect to the bonding strength. The purpose of the research was to (1) evaluate the effect of freezing and thawing cycles on the bonding strength/interface behavior of the composite specimens and (2) to determine the rate at which adhesion strength is lost when undergoing cold weather environment. Based on the test results, the concrete-rock specimens prepared with rough surface show higher bonding strength than the other two surface treated specimens (smooth and semi-rough surface treatments).
Geogrid pull-out modelling using DEM
Authors: Guadagnin Moravia Marcus , Villard Pascal , De Mattos Vidal Delma
Published: June 2019

With the advancement of the use of synthetic reinforcements in geotechnics, a greater understanding of the mechanisms involved in soil-reinforcement interaction is the focus of major research centres on the subject. The topic of this study is the shearing behaviour at interfaces between granular materials and geogrids. The main objective is to provide a more fundamental understanding of some micromechanisms present in this type of interface, which in turn are important to optimize the design of such reinforcement. The numerical modelling of these reinforced structures must deal with the complexity of the material-reinforcement interaction problem; therefore, it requires specific numerical models whose formulations admit localized behaviours in the contacts as well as the granular nature of the material (e.g., soil, gravel, ballast). A robust and flexible way of modelling this problem is through the Discrete Element Method (DEM). The DEM proposes to model this granular nature by representing the soil as interacting constituent particles, whose behaviour is ruled by physical laws defined at the contact points. The numerical approach is desirable since it allows, in an articulated and relatively fast way, studying closely different regions of the interface, in order to identify factors and variables that are important for the problem. The purpose involves the DEM for a 3D modelling of a geogrid pull-out test to calculate the magnitude of forces in different elements of the geogrid (i.e., nodes, longitudinal and transverse members). Preparation of numerical samples has a particular importance in the final results of simulations. Thus, the numerical techniques used to obtain better geometry for the geogrid and a granular assembly with a representative grain rolling effect are also presented in this paper.
A DEM investigation of the shearing behaviour of non-active clays
Authors: Gea Pagano Arianna , Magnanimo Vanessa , Tarantino Alessandro
Published: June 2019

This paper presents the numerical DEM simulation of shear tests on two-dimensional clay-like specimens. Clay particles are modelled as rod-shaped elements made of spherical elementary units. The contact laws implemented in the adopted DEM framework account for both the mechanical interaction developing between particles in contact, and the long-range electro-chemical interaction in the form of Coulombian attraction/repulsion between charged particles. Virtual specimens for shear testing are obtained via the one-dimensional compression and unloading of clay-like particle assemblies, in order to study the effect of different over consolidation ratios on the macroscopic mechanical behaviour. The DEM framework is challenged against its ability to reproduce qualitatively key aspects of the macroscopic behaviour of normally consolidated and over consolidated clays during shearing, including contractive and dilative behaviour, and monotonic and non-monotonic stress-strain behaviour.
Particle-scale insight into transitional behaviour of gap-graded materials – small-strain stiffness and frequency response
Authors: Otsubo Masahide , Tanu Dutta Troyee , Durgalian Manushak , Kuwano Reiko , O'Sullivan Catherine
Published: June 2019

This study aims to develop a fundamental understanding of the role of fine particles on the small-strain stiffness of gap-graded granular soils. Stiffness was measured using cyclic triaxial probes, which give a measure of static stiffness, and dynamic wave propagation data, from which the dynamic stiffness can be measured. Assemblies of loosely packed spherical particles were considered. In the laboratory, local deformation transducers were used to measure the static stiffness, while the dynamic stiffness was calculated from stress wave velocities, measured using planar piezoelectric elements. To relate the particle-scale responses to the overall soil stiffness, complementary discrete element method (DEM) simulations were performed in which both static and dynamic stiffnesses were measured. Both the laboratory and the DEM data indicate that at low fines contents (< 30%) the stiffness decreases with increasing fines content. When the fines content increases from 30% to 35% there is a sharp increase in stiffness with increasing fines content; this is understood to mark the transition point at which the fines start to contribute significantly to the overall behaviour. Analyses of the frequency domain response of shear wave signals revealed that the lowpass frequency increases significantly at this transition point. This observation can be used to develop experimental interpretation protocols to assess to what extent fines are contributing to the overall soil stiffness.
Influence of stress anisotropy on stress distributions in gap-graded soils
Authors: Artigaut Marion , Sufian Adnan , Ding Xiaoxiao , Shire Tom , O'Sullivan Catherine
Published: June 2019

The behaviour of gap graded soils comprising non-plastic fines (sand or silt) mixed with a coarser sand or gravel fraction has received attention from researchers interested in internal instability under seepage loading (a form of internal erosion) as well as researchers interested in load:deformation responses. Skempton and Brogan [1] postulated that resistance to seepage induced instability depends upon the proportion of the overall applied stress that is transmitted by the finer fraction. Shire et al. [2] explored Skempton and Brogan’s hypothesis using DEM simulations to look at the proportion of the applied stress transmitted by the finer fractions (α) in ideal isotropic samples. They showed that at low fines contents (FC< FC*) the average stress transmitted by the finer grains is less than the applied stress (α<1), while for FC>FC+ the fines play a key role in stress transmission (α>1); for FC*<FC< FC+, α depends on the sample density. The current contribution describes a series of constant p’ DEM triaxial test simulations carried out to assess the evolution of stress heterogeneity with shearing. The simulation data generated indicate that a sample can transition from being fines dominated (with the fines transmitting a significant proportion of the applied stress and α ≥1) to coarse or sand- dominated (with α <1) as the material dilates during shear deformation. While α reduces as the samples dilate, the relationship between the α and the sample void ratio is non-trivial. The anisotropy of the coarse-coarse contact network exceeds the overall contact force anisotropy; this indicates that the deviator stress is transmitted through a strong force network passing through the coarse-coarse contacts supported by the fine-coarse contacts.
Constitutive modelling of gassy clay
Authors: Gao Zhiwei , Hong Yi
Published: June 2019

Fine grained sediments with undissolved gas bubbles are widely distributed in the seabed around the world. The gas bubbles are much larger than the clay particles and fit in the saturated clay matrix rather than the pore water. Generally, these bubbles tend to degrade the soil stiffness and strength. But when the difference between the gas and pore water pressure is sufficiently small, pore water in the saturated clay matrix can drain into the cavities, making the void ratio of the saturated matrix smaller, which makes the undrained shear strength of the gassy clay sample higher than that of a saturated one. Such soil response cannot be described based on the assumption that gassy clay is a soil with compressible pore fluid. A new constitutive model for describing the stress-strain relation for gassy clay is proposed. An important feature of the model is that the gassy clay is considered as a composite material with compressible cavities which could be flooded by pore water. Effect of gas cavities on plastic hardening on the saturated matrix is accounted for. The model has been used to predict the response of three gassy clays and good agreement between the test data and model simulations is observed. Potential improvement of the model is discussed.