bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling of simple shear tests on volcanic unsaturated sands
Authors: Moscariello Mariagiovanna , Chen Yanni , Cuomo Sabatino , Buscarnera Giuseppe
Published: October 2020

In landslide susceptibility analysis, a relevant issue is the proper modelling of the complex mechanisms that regulate the failure and post-failure stages. In this paper, simple shear experiments replicating the kinematics of failure in landslide-prone areas are interpreted through an elastoplastic strain-hardening constitutive model for both saturated and unsaturated soils. The material tested is an air-fall volcanic (pyroclastic) soil from Southern Italy which originated from the explosive activity of the Somma-Vesuvius volcanic apparatus. Data from triaxial and shear tests performed on remoulded specimens characterized by saturated and unsaturated conditions are used to calibrate the model parameters. The evolution of shear stress, volumetric and shear strain measured during the experiments are reproduced by means of a model formulation specific for simple shear conditions. To capture the strength emerging under different states of saturation, non-associated flow rule, and a suction-dependent yield surface are used. Examination of the experimental data available for various testing conditions enabled the quantification of the variability of fundamental model constants, such as those controlling frictional resistance and water retention behaviour. To account for such scatter in the physical properties, the constitutive analyses are performed by employing varying model constants within a band of admissible values. The resulting model performance is validated by comparing the simulations with the experimental results at different saturation conditions. The results show that the combination of the proposed model with a data-driven determination of the range of variation of hydro-mechanical properties is crucial to satisfactorily simulate the essential features of the soil response under a variety of simple shear testing regimes.
Numerical investigation on water exchange of shale samples
Authors: Incollingo Sara , Ferrari Alessio , Musso Guido
Published: October 2020

Interest in the hydraulic and mechanical characterization of shales has grown in recent years, because of their application in the context of energy geotechnics. In the frame of nuclear waste disposal shales are considered as host formations for the placements of nuclear waste at high depths. In the frame of hydrocarbon production they are considered as unconventional reservoirs, from which extracting natural gas. Understanding how fluids flow through shales is then a key aspect for both fields of application. This paper focuses on the analysis of the transport of water vapour through laboratory samples. After reviewing the balance and flow laws that govern the transport of fluid in unsaturated porous media, a simplified model is put forward. The model was implemented in a commercial finite element code, and it was used to reproduce the results of a literature study on wetting and drying of Opalinus Clay shale samples, imposed through the vapour equilibrium technique. Back analysis of the water content and volume strains of these specimens suggests that existing models underestimate the actual flow rate of water vapour which takes place at low suctions. The current interpretation also seems to be consistent with microstructural investigations on the interconnection between large pores of this material.
Modelling free gas overpressure in peat layers
Authors: Muraro Stefano , Jommi Cristina
Published: October 2020

The paper assesses fully coupled hydro-mechanical numerical approaches developed for unsaturated soils to model the effect of free gas overpressure on the response of peat layers. A simple linear model is used for the soil skeleton, however, the global response is non-linear due to changes over time of the compressibility of the solid skeleton over the compressibility of the fluid, and solubility of gas in water. The overpressure generated in foundation peat layers by barometric pressure oscillations is modelled, and the results are compared to literature data. The development of pore overpressure upon unloading is analysed as a function of the soil skeleton compressibility, and the consequences on the average stress acting on the soil skeleton are discussed.
Modelling evaporation processes of cement-bentonite mixtures
Authors: Vespo Vincenzo Sergio , Della Vecchia Gabriele , Musso Guido
Published: October 2020

Upon drying, matter and energy are exchanged between the atmosphere and porous media through evaporation, which is a coupled process that involves the simultaneous transport of liquid water, water vapour and heat. At shallow depths, evaporation controls the water content and suction of both natural soils and earthworks, affecting their hydraulic response. This impact is particularly relevant when the earthworks are aimed at the containment of aqueous or non-aqueous pollutants, as in the case of cement bentonite cut-off walls. A coupled model for the transport of liquid water, water vapour and heat through cement bentonite mixtures upon evaporation was formulated. The model considers flow of water driven by both total suction and temperature gradients. Model predictions were compared to experimental results obtained in the laboratory on samples having different sizes and imposed boundary conditions. A good agreement between predicted and measured volumetric water contents was obtained, once defined a suitable dependency of the relative permeability of the mixture on degree of saturation. The results suggest that the proposed formulation correctly accounts for the underlying physical processes, and that it might be used to model the real scale behaviour of cut-off walls.
Very-small to large strain dynamic behaviour of unsaturated sand in a wide range of suction
Authors: Karimezadeh Ali Akbar , Jafarzadeh Fardin , Leung Anthony Kwan , Ahmadinezhad Adel
Published: October 2020

Shear modulus (Gmaxat very small strain andGat large strain) and constraint modulus at very small strain (M) are important soil parameters for static and dynamic analysis in geotechnical applications. However, these dynamic properties of unsaturated soil are rarely reported. In this study, a cyclic simple shear apparatus was newly-modified for allowing both the shear and constrained moduli at both very small and large strains to be measured. Benders or ultrasonic sensors were embedded in an unsaturated soil sample for transmitting/receiving shear- and pressure-wave, respectively. Two very-small-strain tests were conducted to determine theGmax,Mand soil damping ratio of a sand for a wide range of suction covering from the boundary-effect, transition and residual zone of the water retention curve of the sand. In addition, six large-strain cyclic simple shear tests were carried out to investigateG. The test results showed thatGmaxandMwere approximately constant before reaching the air-entry value, but there was a significant increase inGmaxas the sand dried further. Yet,Mdropped within the transition zone, and interestingly when the suction was beyond the residual value,Mincreased.Malong the wetting path was higher than that along the drying path. The damping ratio, on the other hand, first reduced before reaching the air-entry value, but it increased at the transition zone and then decreased within the residual zone. At large strain,G/Gmaxalso increased as suction increased until reaching the residual zone, beyond which the normalised value show substantial decreased.
Effect of coal on mine tailings’ water permeability and water retention
Authors: Vidler Andrew , Buzzi Olivier , Fityus Stephen
Published: October 2020

For safe and efficient mining operations to occur the management of waste materials is required, which often takes the form of geotechnical structures constructed from this waste. The safe use of these structures requires a number of resources, one of these being sufficient information about the waste material properties. For example, the drying process of a tailings dam is predicted with the water retention and permeability of the tailings. When considering coal tailings, which are comprised of coal and mineral soil particles (typically), the presence of coal may be problematic. The localised hydrophobicity of coal molecules may have a unique effect on water permeability and retention; this is relevant to geotechnical analysis where hydrophilic behaviour is assumed. To explore the possible effect of localised hydrophobicity, mine tailings were obtained from a coal mine of the Hunter Valley, NSW, Australia, and the coal fraction was separated via density separation. After this, three materials were available: unchanged mine tailings and a coal and mineral fraction of tailings. The goal was to characterise the three materials and allow deeper insight on what effect the addition of coal has on retention and hydraulic properties. Characterization involved measuring particle size distribution, pore size distribution, soil water retention curve, and saturated water permeability. The results show that there are distinct differences in the water retention and permeability properties of each material, and a number of these differences could be explained by the differing particle/pore sizes observed in each material. However, the coal containing materials desaturated at low suctions (< 10 kPa) compared to the mineral fraction, which could not be explained by particle/pore size differences and points towards localised hydrophobicity as a possible cause.
Water retention and transfer properties of a Green roof volcanic substrate
Authors: Stanic Filip , Delage Pierre , CUI Yu Jun , DE LAURE Emmanuel
Published: October 2020

The water retention curve and the hydraulic conductivity function of a volcanic coarse granular material used as a substrate in an urban green roof in the Paris area was carried out on a newly developed device, in which low suctions were controlled. In the same cell, a hanging column system was used for controlling smaller suctions (up to 32 kPa) and the axis translation technique for larger suctions (up to 50 kPa). Water exchanges were monitored in connected tubes by using a high accuracy differential pressure transducer. The step changes in suction were also used to determine the hydraulic conductivity function by means of Gardner’s method, accounting for the impedance effects due to the high air entry value ceramic porous disk with Kunze and Kirkham’s method. van Genuchten and Brooks and Corey models were used for the water retention curve, but the hydraulic conductivity functions derived from these expressions appeared to lead to a significant under-estimation, confirming the need of operational and simple device for the experimental determination of the hydraulic conductivity function.
Cyclic mechanical loading of unsaturated silty clay soils
Authors: Hailemariam Henok , Wuttke Frank
Published: October 2020

Cyclic mechanical loading of soils due to natural causes such as earthquakes or due to loads coming from structures causes the accumulation of strains and excess pore-water pressures endangering the long term serviceability and stability of the structures built on them. In this study, un-drained cyclic loading tests at 0.1 Hz frequency are carried out on a normally consolidated unsaturated silty clay soil at different deviatoric stresses for up to around 1400 cycles. The results of the tests, which were performed using a recently developed cyclic electromechanical tri-axial device, show a significant dependence of the cyclic mechanical behavior of the silty clay soil, such as in the form of cyclic axial and accumulated plastic strains, on the number of cycles and applied deviatoric stresses.
Failure mode transitions of unconfined granular media from dry to unsaturated to “quasi-fully” saturated states
Authors: Winters Katherine , Berry Woodman , Seimens Greg , Taylor Oliver-Denzil
Published: October 2020

Recent research has shown discrepancies between the prevailing mathematical representations of near-surface shear strength and the observed shear strengths. This investigation focuses on three granular materials, i.e., 1) poorly-graded, medium-fine silica-quartz sand, 2) an engineered silica-quartz mix of 3.38-mm and 0.638-mm sub-angular particles, and 3) an angular fused quartz sand. Specimens were tested under load-controlled conditions at variable saturations in order to identify and quantify the influence of suction on the granular structures and failure modes. All three materials exhibited localized radial particle force chain buckling failures in unconfined drained dry (UDκ) conditions and classical shear failures in the unconfined drained unsaturated shear (UDP) conditions. In unconfined drained suction failures (UDS) conditions, the poorly-graded, medium-fine silica-quartz sand exhibited a bulging and sloughing failure without weeping, while the other two materials wept and then held loads before failure. Thus, it is suggested that the pore fluid had a predominate lubrication (strength weakening) effect, and the assumption of structure stiffening (strength increase) from matric suction may not be valid at near-surface conditions for sub-angular silica-quartz materials but is valid for the angular fused quartz.
A comparative assessment of chemical stabilisers including waste materials, for the treatment of swelling-shrinking soils
Authors: Mavroulidou Maria , Gray Christopher , Gumbochuma Fortunate , Gunn Michael J.
Published: October 2020

This paper assesses comparatively the performance of a number of innovative soil stabilisers for the treatment of a highly swelling-shrinking soil, against that of commercial calcium lime. The production of lime, a most common soil stabiliser, involves high energy consumption, carbon dioxide emissions and the depletion of natural raw materials. Alternatives are actively sought, in particular industrial wastes and by-product materials or lower energy demand cements e.g. reactive magnesia (MgO) cements. In this paper calcium lime, reactive magnesia, industrial wastes and mixes of these with lime are comparatively assessed, based on a number of conventional measures of the propensity of a soil to swell, i.e. plasticity characteristics and swelling characteristics (swelling strains, swelling pressures, swelling indices). Furthermore, as expansive soils are typically in an unsaturated state hence sensitive to both changes in water content and suction, filter paper testing was performed to provide additional evidence of the effect of the treatments on the swelling/shrinking soil. According to the main findings, for the treatment of swelling shrinking soils, binders coming from the paper recycling industry show most promise as alternatives to lime; reactive magnesia cement had a smaller effect than calcium based stabilisers in improving the swelling-shrinking of the soil, yet it also suppressed swelling and shrinkage considerably; it thus shows potential for use as an alternative to common soil stabilisers (Portland cement and calcium lime) to alleviate the environmental impact of the latter.
Modelling Unsaturated Soil Response Beyond Residual Suction State via Vapor-Pressure Controlled Triaxial Testing
Authors: Morvan Mathilde , Patil Ujwalkumar D. , Hoyos Laureano R. , Congress Surya S. C. , Puppala Anand J.
Published: October 2020

Most of the previous research has been focused on developing and validating constitutive models to predict response of unsaturated soils in low-medium suction range. However, there is a scarcity of efforts in developing soil models to simulate its mechanical response in high suction range, particularly above the residual suction. This article presents a new constitutive model introducing net stress and suction as two independent variables. Furthermore, non-associative flow rule incorporating modified stress-dilatancy relationship to take unsaturated state into account is introduced to improve the model results in low-medium to high suction range. The essential soil model parameters are calibrated using suction-controlled triaxial test results for predictions of compacted silty sand response at high values of total suction above residual suction. Preliminary simulations show that proposed model can reasonably simulate the post-peak strain softening response obtained from suction-controlled CTC tests above residual suction value with reasonable accuracy. Although, the proposed model captures initial compression followed by dilation volumetric response with reasonable accuracy, it needs some improvements to be able to capture volumetric response accurately over entire suction range.
Analysis of the suction evolution during direct shear test in a silty sand soil
Authors: AL-Emami Omar , M Medero Gabriela , A M Marinho Fernando , Sutman Melis
Published: October 2020

Shear strength of soils is one of the essential parameters for analysing and solving divers geotechnical problems (e.g. the bearing capacity of shallow footings pile foundations, slope stability and earth embankments). In this study, a series of conventional large-scale (300 X 300 mm) direct shear tests were carried out on saturated and constant water content silty sand specimens at ei = 0.6 and 1.0 tested under applied vertical stresses of 100, 200, or 400 kPa to investigate the influence of matric suction on the shear strength characteristics of the tested material. A loading steel cap was modified to allow the direct measurements of the matric suction using two commercial available Equitensiometer suction probes (EQ3). The experimental program indicated that, for both studied void ratios, the obtained shear strength of specimens under constant water content is found to be distinctly greater than those obtained from saturated samples. The results showed that the samples compacted at ei = 1.0 exhibited collapse behaviour during saturation stage, whereas same samples did not show any volume change during stabilisation stage when tested under constant water content condition. The study results also showed that the matric suction reduction during consolidation stage depends on initial void ratio of the tested samples as well as the level of applied vertical stress. Moreover, the matric suction evolution during shearing process of both studied void ratios specimens decreased with increasing the level of applied vertical stress.
Preliminary investigation on the water retention behaviour of cement bentonite mixtures
Authors: Trischitta Paolo , Cosentini Renato Maria , Della Vecchia Gabriele , Sanetti Gianluigi , Musso Guido
Published: October 2020

Cement bentonite mixtures are often used to build slurry walls for the containment of both aqueous and non aqueous pollutants, due to their quite low hydraulic conductivity and relatively high ductility and strength. Although their hydro-mechanical behaviour in saturated conditions has been studied in the past, a part of the slurry wall is expected to rest above the groundwater level. The hydraulic characterization in unsaturated conditions is then particularly relevant to evaluate the performance of the barrier, especially when it is aimed at containing non aqueous pollutant liquids which are lighter than water (LNAPL). These non wetting fluids rest above the water table and their penetration is possible just if the barrier is unsaturated. This paper presents some preliminary results of a laboratory characterization of the water retention behaviour of three different cement bentonite mixtures. The mixtures, prepared at cement – bentonite mass ratios ranging from 4:1 to 6:1, were immersed in water and cured for 28 days. Their water retention behaviour was then determined along drying and wetting paths through different techniques, namely axis translation, filter paper and vapour equilibrium. In the high suction range, the water content – suction relationship was found to be independent of cement-bentonite ratio. In the low suction range, the water content at a given suction was found to decrease for increasing cement bentonite ratios.
Characterization of Sand and Zeolite Stabilized Expansive Soil as Landfill Liner Material under Environmental and Climatic Effects
Authors: Öncü Şerife , Bilsel Huriye
Published: October 2020

This study focusses on the assessment of sand stabilized expansive soil as possible landfill liner materials to be utilized in a semi-arid area. Zeolite was also used as an alternative material to sand, mixing it with the expansive soil forming a stable structure with improved properties. Durability analysis of expansive soil-sand (NS) and expansive soil-zeolite (NZ) mixtures was studied to investigate the climatic and environmental effects on the sustainability of the proposed materials. The climatic effect is studied in terms of cyclic swell-shrinking and the environmental effect, mainly due to temperature elevations in the landfills, is studied in swell-compressibility tests. Cyclic swell-shrink tests and temperature variations (25°C, 40°C and 60°C) were applied on 28-day cured samples of NS and NZ mixtures in order to evaluate their resistance to climatic and environmental changes. Experimental findings showed that swelling potential and axial shrinkage were reduced with the increasing of wetting-drying cycles of both NS and NZ samples. The biggest variation of swell potential and axial shrinkage occurred at 7th cycle for NS (28-d) and 8th cycle for NZ (28-d) soil specimens. Primary swell percentage decreased with the increase of temperature in NS group, whereas, a reverse behavior was observed in NZ group.
Effect of external hydraulic head on swelling of unsaturated clay
Authors: Nachum Shay , Talesnick Mark , Frydman Sam
Published: October 2020

Laboratory testing of the one-dimensional swell of soil (usually unsaturated clay) is generally performed according to ASTM standard D4546. The standard procedure requires that “the specimen is inundated with test water and the one-dimensional wetting-induced swell or collapse strain is measured”. This procedure undoubtedly provides an upper limit to the swell which may be expected under field conditions, and may be relevant to cases in which low lying areas are expected to be inundated as a result of a wetting episode. However, in other cases, wetting of the soil may result from less extreme conditions - for example absorption of water from underlying, wetted layers, or soaking of the lower portion of a swelling layer and resultant upward wetting due to suction forces. The present paper describes a laboratory investigation of the effect of external hydraulic head on swell. The results demonstrate the importance of applying test conditions consistent with those expected in the field situation.
Cyclic behaviour of an unsaturated silty soil subjected to hydro-mechanical damage
Authors: Nishimura Tomoyoshi
Published: October 2020

The dynamic behaviour of unsaturated soil subjected to cyclic loading is considered using two stress state variables, net normal stress and matric suction. Though the influence of excess pore-water pressures in fully saturated soils has been investigated through experimental works for decades, it is significant in practice for unsaturated soil dynamic behaviour to be compared to saturated soil dynamic strength-deformation properties. Matric suction can be described as a scalar, which is useful in establishing safety factors and in mathematical simulations. This study focused on the dynamic behaviour of unsaturated soil leading to liquefaction failure. Solving practical problems requires considering the properties of unsaturated soil subjected to creep before introducing dynamic loading effects. This testing program consisted of a creep test and a cyclic loading test. Notably, a low suction range of soil structure is closely related to large deformations or leads to failure impacting the resistance of soil particle cohesion, including the macro-micro structure. Creep force was applied under lateral confining pressure, and suction measurements are indicating a gradual growth of excess pore-water pressure. Moreover, this study considered a dynamic triaxial compression test under the undrained condition for unsaturated soil with suction and creep history.
Fall cone test on biopolymer-treated clay
Authors: Zhanbo Cheng , Jing Ni , Haotian Ding , Xueyu Geng
Published: October 2020

Fall cone tests were conducted to evaluate the consistency variations of clay soils treated with six types of biopolymers, e.g. carrageenan kappa gum (KG), locust bean gum (BG), xanthan gum (XG), agar gum (AG), guar gum (GG) and sodium alginate (SA) at various concentrations (e.g. between 0.1% to 5% biopolymer to soil mass ratio). The dependences of shear viscosity on water content, and undrained shear strength on water content were established. The results indicated that KG and SA increased the liquid limit (LL) of treated soils after the biopolymer content exceeded a certain limit (e.g. 0.5%), BG and GG contributed to a peak point in LL at biopolymer concentration of 1% to 2%, while XG and AG almost did not change the LL at all. The plastic limit (PL) was about 25% to 50% of the LL, leading to a trend of plasticity index (PI) similar to liquid limit. In order to further simplify the testing procedure and get the Atterberg limits for biopolymer-treated soil, one-point method was adopted.
Hydromechanical behaviour of hydrophobised soils of varying degrees of saturation: a comprehensive review
Authors: Zhou Zheng , K Leung Anthony
Published: October 2020

Artificially hydrophobised soil has been recently considered as an alternative engineering material that may be used to reduce water (or rainfall) infiltration and hence to enhance the geotechnical performance and stability of earthen structures such as slope and landfill covers. Thorough research has been conducted to study the hydrological behaviour and properties of hydrophobised soil in the last four decades. Mechanical properties of this kind of material has received some attention only since 2011, focusing on how hydrophobisation may affect the shearing behaviour and shear strength parameters including friction angle. Knowledge on the effects of hydrophobisation on other hydromechanical properties of soil that are relevant to geotechnical engineering applications is lacking. This paper therefore aims to conduct a comprehensive review and carry out some reinterpretation of selected literature with references to existing theories or frameworks of soil mechanics. Attempts are made to generalise and highlight not only the shearing behaviour, but also dilatancy, compressibility and stiffness of hydrophobised soil. Research gaps that may be worth exploring are given after the review.
Development of a THMC code for bentonites in COMSOL Multiphysics
Authors: Yustres Ángel , López-Vizcaíno Rubén , Cabrera Virginia , Navarro Vicente
Published: October 2020

The proposed use of active clays for the isolation of radioactive wastes in deep geological repositories has been followed by a deeper understanding of this type of soils. This increased knowledge has led to the need for both conceptual and numerical models capable of capturing the main trends in behaviour and the different couplings between different physical-chemical phenomena. In addition, the model must have a high degree of flexibility that enables it to accommodate future developments or new relevant phenomena. This work presents a numerical THMC code developed entirely on the COMSOL Multiphysics numerical implementation platform, which provides the required adaptability. This model includes, for the first time in this environment, a reactive transport model in unsaturated porous media for a relevant geochemical system (consistent with the MX-80 bentonite) together with a THM model based on a double porosity approach. The chemical potentials of water and solutes are used for the definition of thermodynamic equilibria between both porosity levels. Trends in the behaviour of a bentonite sample under oedometric conditions are satisfactorily simulated in response to a process of saturation and change in salinity conditions. Variations in swelling pressure, porosity distribution or dissolution/precipitation of the main accessory minerals are analysed and explained by means of the proposed conceptual model.
Hydro-mechanical behaviour of a pellets based bentonite seal: Numerical modelling of lab scale experiments
Authors: Gramegna Liliana , Collin Frédéric , Talandier Jean , Imbert Christophe , Charlier Robert
Published: October 2020

In most of the concept designs for nuclear waste disposals, bentonite-based materials are used to seal underground galleries and shafts. In order to assess the safety of such engineered barriers and to provide a good prediction for the material behaviour, a number of experimental campaigns and constitutive models have been developed mainly focusing on bentonite compacted blocks. On the other hand, in recent years, the use of high density bentonite pellets combined with powdered bentonite has also been considered as an interesting alternative. The bentonite pellets mixtures present a prominent initial heterogeneity level as a result of the inter-pellets porosity, which evolves strongly during hydration. This paper aims to present the numerical modelling strategy adopted for a swelling pressure test on pellets mixture carried by CEA (France). Taking advantage of the finite element code LAGAMINE, the Barcelona Basic model is considered for the bentonite mechanical behaviour and the double porosity model proposed by [1] is used for the water retention behaviour and permeability evolution. Given the already-known complexity of the multiphysical and multiscale coupled processes taking place during bentonite-hydration, the obtained numerical results are in good agreement with experimental measurements. Especially, the non-monotonic evolution of the swelling pressure during the hydration phase is well captured by this model, which is always a challenge for this type of problem.
Discrete Element Modelling for biocemented sand: effect of calcite distribution at the microscopic scale
Authors: Abbas Mohammad , Kunhappan Deepack , Dadda Abdelali , Geindreau Christian , Emeriault Fabrice , Esnault-Filet Annette , Garandet Aurelie
Published: October 2020

The mechanical efficiency of the biocementation process is directly related to the microstructural properties of the biocemented soil, such as, the volume fraction of calcite, its distribution within the pore space (whether localized at the contact between grains or over the grain surfaces) and the contact properties: coordination number, contact surface area, contact orientation, type of contacts (frictional even after treatment, purely cohesive via a calcite bridge or combining friction between particles and cohesion of the localized calcite). Dadda et al, (2018) have used microscopic properties computed from 3D images obtained by X-ray tomography of biocemented sand samples with different levels of biocementation as an input in current analytical models to estimate the elastic properties (Young’s and shear modulus) and the strength properties (Coulomb cohesion). They pointed out the important role of some microstructural parameters, notably those related to the contact, on such effective parameters. However, the precise evaluation of the effect of microstructural parameters such as the contact surface distribution on the global mechanical behaviour of the soil requires the use of more advanced modelling methods. The paper presents the results of Discrete Element Modelling of triaxial tests with the open source code Yade in which the real microstructural properties of biocemented soil computed on 3D X-ray microtomography images are used as input parameters. A particular attention has been paid to take into account the actual distribution of contact surface in the model and not only the average value. It appears that the model is then able to reproduce the evolution of the macroscopic properties (in particular that of the cohesion) with the calcite content.
Effect of the soil type on the biocementation process by enzymatic way
Authors: Venda Oliveira Paulo J. , Freitas Luís D.
Published: October 2020

The effect of the enzymatic CaCO3 precipitation on the behaviour of four soils (from a poorly graded sand to a fine and organic soil) is studied in this work. The analysis is based on the results of UCS tests, where the results from the non-stabilised specimens are compared with specimens stabilised with a urease concentration of 8 kU/L and an equimolar solution of urea-CaCl2 of 0.5 mol/L. Additionally, pH and scanning electron microscopy (SEM) tests with energy dispersive X-ray (EDX) analyses are performed to analyse the microstructure and the local chemical composition. The results of the UCS tests show that, in the case of the sandy and silty soils, the process of enzymatic CaCO3 precipitation potentiates the strengthening of the soils while, in the organic soil, a detrimental effect is observed. The SEM tests show the existence of vestiges of calcium in the biostabilised soils studied.
Experimental study on the effect of chitosan biopolymer on sandy soil stabilization
Authors: Shariatmadari Nader , Reza Mohammad , Tasuji Amiri , Ghadir Pooria , Javadi A. Akbar
Published: October 2020

Due to the environmental impacts of conventional soil stabilization materials, such as cement, ongoing efforts have been carried out by different researchers to find alternative economical materials for substitution. Biopolymers are environmentally friendly materials that are widely used in different geoenvironmental applications such as removal of heavy metals from contaminated soils, reduction of soil hydraulic conductivity, erosion control, and soil improvement. In this research the feasibility of using chitosan biopolymer for sandy soil stabilization has been studied. The effects of biopolymer content, curing time, and curing conditions have investigated using unconfined compression tests. The results indicated that incorporation of chitosan has the potential to increase the interparticle cohesion between the particles and considerable improvement of sandy soil mechanical properties. After initial strengthening of the soil, some strength reduction over time was observed due to the degradation characteristics of the chitosan. With regards to the curing condition, better performances at dry condition compare to the wet and saturated environment were achieved. In addition to soil mechanical properties, the pore plugging effect of chitosan biopolymer on highly permeable sandy soil has been studied in this study.
Charge Density Distribution Model in Self-Organizing Cloud
Authors: Kumykov Tembulat
Published: October 2020

The paper considers a charge distribution model in a thundercloud presenting a self-organizing system in view of its fractal structure. An analytical solution to the model equation is obtained. Using numerical calculations, the distribution of charges in the fractal medium is shown and a comparative analysis of the existing models is carried out.
An automated method for detecting sporadic effects in cosmic rays
Authors: Geppener Vladimir , Mandrikova Bogdana
Published: October 2020

The paper proposes an automated method for analyzing data from neutron monitors and detecting sporadic effects in the dynamics of cosmic rays. The method is based on the use of LVQ neural networks and wavelet transform constructions. It is shown that the method allows detecting sporadic effects of different amplitudes and durations and evaluating their parameters. A numerical implementation of procedures for detecting sporadic effects and assessing their intensity is carried out. The questions of choosing the parameters of algorithms are investigated and ways of their optimization are proposed. On the example of the April 13-14 2013 and March 8-9 2014 events, the effectiveness of the method for detecting sporadic effects in cosmic rays preceding and accompanying magnetic storms is shown.
Low-frequency parametric systems in the shallow sea
Authors: Tarasov Sergei , Jianjun Zhu , Pivnev Petr , Gubko Mikhail
Published: October 2020

The theoretical model of acoustic wave propagation in the ice-water layer is developed, with, taking into account the velocity dispersion. New opportunities for monitoring the marine environment on long routes, including those covered with ice, are discussed when using parametric sonar antennas. The results of research demonstrating single-mode excitation of a waveguide by a parametric array in a wide frequency band are presented. The possibility of compression of a broadband signal during its propagation, as a result of waveguide dispersion, which leads to an increasing of signal intensity, is shown. The results of experimental studies of the propagation characteristics of a wide-band acoustic signal of a parametric hydroacoustic array in a shallow sea are presented.
Principles of organizing earthquake forecasting based on multiparameter sensor-WEB monitoring data
Authors: Pulinets Sergey , Ouzounov Dimitar , Davidenko Dmitry , Budnikov Pavel
Published: October 2020

The paper describes an approach that allows, basing on the data of multiparameter monitoring of atmospheric and ionospheric parameters and using ground-based and satellite measurements, to select from the data stream a time interval indicating the beginning of the final stage of earthquake preparation, and finally using intelligent data processing to carry out a short-term forecast for a time interval of 2 weeks to 1 day before the main shock. Based on the physical model of the lithosphere-atmospheric-ionospheric coupling, the precursors are selected, the ensemble of which is observed only during the precursory periods, and their identification is based on morphological features determined by the physical mechanism of their generation, and not on amplitude selection based on statistical data processing. Basing on the developed maquette of the automatic processing service, the possibility of real-time monitoring of the situation in a seismically active region will be demonstrated using the territory of the Kamchatka region and the Kuril Islands.
The internet-community response to the Mexican Earthquake of February 1, 2019
Authors: Tertyshnikov Alexandr V.
Published: October 2020

Signs of the threat of the Mexican earthquake of February 1, 2019, are presented according to estimates of the recurrence of query words in Internet electronic publications. These estimates (information signals) have been determined using the Internet search engines.

Before the earthquake, an increase in the recurrence of query words semantically related to seismic-hazard precursors was revealed in electronic publications relative to the seismically hazardous region. After the earthquake, the activity of the Internet community decreases.
Interdisziplinär integriert oder dezentral verteilt? Versorgungssettings im Kontext feminisierender Genitaloperationen – Studienprotokoll zur Hamburger TransCare-Studie
Authors: Köhler Andreas , Strauß Bernhard , Briken Peer , Riechardt Silke , Fisch Margit , Nieder Timo O.
Published: October 2020

Hintergrund Geschlechtsdysphorie (GD, ehemals Transsexualität) bezeichnet einen Leidensdruck, der sich aus der Inkongruenz zwischen den körperlichen Geschlechtsmerkmalen und dem Erleben des eigenen Geschlechts ergeben kann (Geschlechtsinkongruenz: GIK). Die Gesundheitsversorgung von Personen mit GIK/GD bezieht sich v. a. auf geschlechtsangleichende Maßnahmen (z. B. Hormonbehandlung) und Unterstützung bei assoziierten Bedürfnissen (z. B. durch Psychotherapie). Zudem gelten genitalchirurgische Eingriffe als effektive Verfahren zur Reduktion von GIK/GD und zur Verbesserung der psychischen Gesundheit und Lebensqualität. Als evidenzbasiert gilt eine integrative Gesundheitsversorgung, bei der die beteiligten Bereiche interdisziplinär kooperieren.

Ziel der Studie Bei der medizinischen Versorgung von Patient_innen mit GIK/GD lassen sich grundsätzlich zwei Settings unterscheiden: interdisziplinär integriert an einem Standort vs. dezentral verteilt über mehrere Standorte. Die Trans-Gesundheitsversorgung in Deutschland ist bisher weitgehend dezentral organisiert. Wie sich das Versorgungssetting auf die Wirksamkeit und Qualität genitalangleichender Operationen auswirkt, wurde bisher nicht untersucht. Ziel der TransCare-Studie ist es daher, prospektiv katamnestisch das psychosoziale und klinische Outcome von Patient_innen mit GIK/GD zu untersuchen, die eine feminisierende Genitaloperation in Anspruch nehmen, und auf die möglichen Auswirkungen des Versorgungssettings (interdisziplinär integriert vs. dezentral verteilt) hin zu vergleichen.

Methodik Im Zuge eines naturalistischen Längsschnittdesigns soll eine möglichst praxisnahe Stichprobe rekrutiert und die teilnehmenden Patient_innen prospektiv befragt werden.

Ergebnisse Die Studienergebnisse sollen Erkenntnisse über die Rolle des Versorgungssettings im Rahmen der genitalchirurgischen Behandlung von Patient_innen mit GIK/GD hervorbringen.

Schlussfolgerung Auf Basis der TransCare-Studie soll die Versorgungsqualität empirisch fundiert verbessert werden.
Injuries to the Coronoid Process of the Ulna with Involvement of the
Lesser Sigmoid Notch
Authors: Rausch Valentin , Neugebauer Sina , Leschinger Tim , Müller Lars , Wegmann Kilian , Hackl Michael
Published: October 2020

Introduction This study aimed to describe the involvement of the lesser
sigmoid notch in fractures to the coronoid process. We hypothesized that
injuries to the lateral aspect of the coronoid process regularly involve the
annular ligament insertion at the anterior lesser sigmoid notch.

Material and Methods Patients treated for a coronoid process fracture at
our institution between 06/2011 and 07/2018 were included. We excluded patients
< 18 years, patients with arthritic changes or previous operative treatment
to the elbow, and patients with concomitant injuries to the proximal ulna. In
patients with involvement of the lesser sigmoid notch, the coronoid height and
fragment size (anteroposterior, mediolateral, and craniocaudal) were
measured.

Results Seventy-two patients (mean age: 47 years ± 17.6) could be included
in the study. Twenty-one patients (29.2%) had a fracture involving the lateral
sigmoid notch. The mean anteroposterior fragment length was 7 ± 1.6 mm. The
fragment affected a mean of 43 ± 10.8% of the coronoid height. The mean
mediolateral size of the fragment was 10 ± 5.0 mm, and the mean cranio-caudal
size was 7 ± 2.7 mm.

Conclusion Coronoid fractures regularly include the lesser sigmoid notch.
These injuries possibly affect the anterior annular ligament insertion which is
important for the stability of the proximal radioulnar joint and varus stability
of the elbow.
Path Analysis on Determinants of Childhood Obesity and Associated Risk Factors of Cardiovascular, Renal, and Hepatic Diseases: The CASPIAN-V Study
Authors: Mansouri Vahid , Mansourian Marjan , Qorbani Mostafa , Riahi Roya , Karimi Rahele , Motlagh Mohammad Esmaeil , Heshmat Ramin , Kelishadi Roya
Published: October 2020

The interaction between several lifestyle and obesogenic environmental factors is considered as the main underlying factor for the escalating trend of childhood obesity and its adverse consequences. In this study, we assessed the mutual influence of lifestyle habits and body mass index (BMI) as well as risk factors for cardiometabolic, hepatic, and renal disorders to define the causality power of each item. This nationwide cross-sectional study was conducted as the fifth round of a school-based surveillance program. Overall, 14,800 students living in Iran were studied, and blood samples were obtained from 4,200 of them. Demographic factors, anthropometric and biochemical measures were used to define lifestyle-related latent variables as well as cardiac, renal, and hepatic risk indicators. Total, direct, and indirect effects between factors were analyzed using the standardized regression weights for each pathway. Data from 14,274 students (participation rate of 99%) and 3,843 blood samples were included. All of the latent variables had a significant direct effect on BMI, with the most potent effect of unhealthy nutrition (β ≅ 0.63) in boys and girls. BMI has significant direct effects on risk indicators of cardiovascular, renal, and hepatic diseases with the most powerful effect on cardiovascular risk factors (β ≅  − 0.08). The most important predisposing factor for obesity was unhealthy nutrition, whereas increased activity, adequate sleep, and better hygiene had protective roles. BMI shows the strongest association with indicator of cardiovascular diseases. These findings underscore the importance of implementing public health programs for the prevention of chronic noncommunicable diseases.
Pediatric COVID-19 and the Factors That May Mitigate Its Clinical Course
Authors: Abdel-Aziz Mosaad , Abdel-Aziz Nada M. , Abdel-Aziz Dina M. , Azab Noha
Published: October 2020

The clinical manifestations of novel coronavirus disease 2019 (COVID-19) vary from mild flu-like symptoms to severe fatal pneumonia. However, children with COVID-19 may be asymptomatic or may have mild clinical symptoms. The aim of this study was to investigate clinical features of pediatric COVID-19 and to search for the factors that may mitigate the disease course. We reviewed the literature to realize the clinical features, laboratory, and radiographic data that may be diagnostic for COVID-19 among children. Also, we studied the factors that may affect the clinical course of the disease. Fever, dry cough, and fatigue are the main symptoms of pediatric COVID-19, sometimes flu-like symptoms and/or gastrointestinal symptoms may be present. Although some infected children may be asymptomatic, a recent unusual hyperinflammatory reaction with overlapping features of Kawasaki's disease and toxic shock syndrome in pediatric COVID-19 has been occasionally reported. Severe acute respiratory syndrome-coronvirus-2 (SARS-CoV-2) nucleic acid testing is the corner-stone method for the diagnosis of COVID-19. Lymphocyte count and other inflammatory markers are not essentially diagnostic; however, chest computed tomography is highly specific. Factors that may mitigate the severity of pediatric COVID-19 are home confinement with limited children activity, trained immunity caused by compulsory vaccination, the response of the angiotensin-converting enzyme 2 receptors in children is not the same as in adults, and that children are less likely to have comorbidities. As infected children may be asymptomatic or may have only mild respiratory and/or gastrointestinal symptoms that might be missed, all children for families who have a member diagnosed with COVID-19 should be investigated.
An Interesting Case of Bilateral Upper Limb Wasting: Hirayama Disease
Authors: Eugin Priscilla Rubavathy , Chinnusamy Manokaran , Janakiraman Sathiyanarayanan
Published: October 2020

Hirayama disease is a rare neurologic disease and is characterized by insidious unilateral or bilateral muscular atrophy and weakness of the forearms and hands without sensory or pyramidal signs. Our patient presented with bilateral upper limb wasting, which is a rarer variant of motor neuron disease. The diagnosis of Hirayama disease is based on dynamic magnetic resonance imaging (MRI). This case displays how dynamic cervical spine MRI can pick up dynamic cord compression and contributes to zero in the diagnosis of Hirayama disease.