Tensile strength and failure behavior of rock-mortar interfaces: Direct and indirect measurements

The tensile strength at the rock-concrete interface is one of the crucial factors controlling the failure mechanisms of structures,such as concrete gravity dams.Despite the critical importance of the failure mechanism and tensile strength of rock-concrete interfaces,understanding of these factors remains very limited.This study investigated the tensile strength and fracturing processes at rock-mortar interfaces subjected to direct and indirect tensile loadings.Digital image correlation(DIC)and acoustic emission(AE)techniques were used to monitor the failure mechanisms of specimens subjected to direct tension and indirect loading(Brazilian tests).The results indicated that the direct tensile strength of the rock-mortar specimens was lower than their indirect tensile strength,with a direct/indirect tensile strength ratio of 65%.DIC strain field data and moment tensor inversions(MTI)of AE events indicated that a significant number of shear microcracks occurred in the specimens subjected to the Brazilian test.The presence of these shear microcracks,which require more energy to break,resulted in a higher tensile strength during the Brazilian tests.In contrast,microcracks were predominantly tensile in specimens subjected to direct tension,leading to a lower tensile strength.Spatiotemporal monitoring of the cracking processes in the rock-mortar interfaces revealed that they show AE precursors before failure under the Brazilian test,whereas they show a minimal number of AE events before failure under direct tension.Due to different microcracking mechanisms,specimens tested under Brazilian tests showed lower roughness with flatter fracture surfaces than those tested under direct tension with jagged and rough fracture surfaces.The results of this study shed light on better understanding the micromechanics of damage in the rock-concrete interfaces for a safer design of engineering structures.

Identity(ies)and Transnationalization of Brazilian Evangelical Churches in Portugal:Case study of World Cathedral of Hope and Victory in Christ Churches

The presence of evangelicals in Brazil is a social and religious phenomenon that has aroused interest of many scholars due to its rapid and significant expansion in recent decades and its projection beyond national borders.Among evangelical denominations that stand out in this scenario are Pentecostal churches,which have developed intense missionary activity in several countries,including Europe.In this article,we intend to analyze features and challenges of Brazilian evangelical churches:World Cathedral of Hope(CIME)(Catedral Mundial da Esperança-ICME)and Assembly of God Victory in Christ(ADVEC)(Assembleia de Deus Vitória em Cristo-ADVEC)that operate in Portugal,seeking to understand issues of identity and belonging of these communities,their models of transnationalization,its evangelization strategies and its adaptations to Portuguese context,in the period from 2000 to 2020.

From Rejection to Embracement:The Catholic Perception of Spiritism in Brazil

The history of the relationship between Spiritism and Catholicism in Brazil can be traced through pivotal moments in the trajectory of the First Republic and the religious field since the 19th century,reflecting Brazil’s evolution into a modern,urban,and industrial society.Introduced to Brazil in the 1880s,Spiritism initially faced severe opposition from the Catholic Church,being dismissed as superstition and demon worship due to its engagement with death and spirits.Unlike Christianity,Spiritism denies the divinity of Jesus,the resurrection,and the sanctity of Church sacraments,viewing demons and angels merely as disembodied souls at different spiritual stages.Early perceptions were further complicated by the mixing of Spiritism with African and indigenous rites,which led critics to associate it with madness and mental health threats.However,the relationship between Catholicism and Spiritism in Brazil has evolved positively,particularly following the popularization of Spiritism by figures like Chico Xavier.Modern Brazilian society,characterized by increased education and religious syncretism,has grown more tolerant of diverse practices and beliefs,diminishing historical prejudices against Spiritists.This qualitative study,drawing on scholarly research and first-hand interviews,reveals that Spiritism's acceptance among Brazilian Catholics is due to its convergence with contemporary social values and the evolving profile of the average Catholic.Despite possessing a religion-like character,Spiritism is seen less as a distinct religion and more as a complementary set of practices and beliefs that enhance Catholic faith.This phenomenon mirrors the integration of Agama Hindu practices,reinforcing rather than undermining traditional religious identities.

SIT.net: SAR Deforestation Classification of Amazon Forest for Land Use Land Cover Application

The process of turning forest area into land is known as deforestation or forest degradation. Reforestation as a fraction of deforestation is extremely low. For improved qualitative and quantitative classification, we used Sentinel-1 dataset of State of Para, Brazil to precisely and closely monitor deforestation between June 2019 and June 2023. This research aimed to find out suitable model for classification called Satellite Imaging analysis by Transpose deep neural transformation network (SIT-net) using mathematical model based on Band math approach to classify deforestation applying transpose deep neural network. The main advantage of proposed model is easy to handle SAR images. The study concludes that SAR satellite gives high-resolution images to improve deforestation monitoring and proposed model takes less computational time compared to other techniques.

Majority of Brazilians Expect Unfaithful Spouse?

标题让人吃惊！Unfaithful Spouse者,有外遇之配偶也。而在巴西居然大多数的已婚者盼望“外遇”。更有甚者,巴西的一教授认为,已婚者有一个私 通者,已经融入了该国的文化！巴西的more liberal in its sexual mores(风俗;习惯;民德;道德观念)令英美“汗颜”！】

Microscopic damage evolution of anisotropic rocks under indirect tensile conditions: Insights from acoustic emission and digital image correlation techniques

The anisotropy induced by rock bedding structures is usually manifested in the mechanical behaviors and failure modes of rocks.Brazilian tests are conducted for seven groups of shale specimens featuring different bedding angles. Acoustic emission (AE) and digital image correlation (DIC) technologies are used to monitor the in-situ failure of the specimens. Furthermore, the crack morphology of damaged samples is observed through scanning electron microscopy (SEM). Results reveal the structural dependence on the tensile mechanical behavior of shales. The shale disk exhibits compression in the early stage of the experiment with varying locations and durations. The location of the compression area moves downward and gradually disappears when the bedding angle increases. The macroscopic failure is well characterized by AE event location results, and the dominant frequency distribution is related to the bedding angle. The b-value is found to be stress-dependent.The crack turning angle between layers and the number of cracks crossing the bedding both increase with the bedding angle, indicating competition between crack propagations. SEM results revealed that the failure modes of the samples can be classified into three types:tensile failure along beddings with shear failure of the matrix, ladder shear failure along beddings with tensile failure of the matrix, and shear failure along multiple beddings with tensile failure of the matrix.

Effects of 3D deformation and nonlinear stress–strain relationship on the Brazilian test for a transversely isotropic rock

To improve the accuracy of indirect tensile strength for a transversely isotropic rock in the Brazilian test, this study considered the three-dimensional (3D) deformation and the nonlinear stress–strain relationship. A parametric study of a numerical Brazilian test was performed for a general range of elastic constants, revealing that the 3D modeling evaluated the indirect tensile strength up to 40% higher than the plane stress modeling. For the actual Asan gneiss, the 3D model evaluated the indirect tensile strength up to 10% higher and slightly enhanced the accuracy of deformation estimation compared with the plane stress model. The nonlinearity in stress–strain curve of Asan gneiss under uniaxial compression was then considered, such that the evaluated indirect tensile strength was affected by up to 10% and its anisotropy agreed well with the physical intuition. The estimation of deformation was significantly enhanced. The further validation on the nonlinear model is expected as future research.

Analysis of stresses at the center of transversely isotropic Brazilian disk

This article presents the stresses at the center of a Brazilian disk(BD)for transversely isotropic rocks.It is shown that the solution of stresses at the center of an anisotropic disk is a function of the disk radius and the magnitude of applied load,as well as the material orientation with respect to the load axis and two dimensionless ratios with specific physical meanings and limitations.These two dimensionless parameters are the ratios of Young’s modulus and apparent shear modulus,although the ratio of apparent shear modulus will be eliminated if the Saint-Venant assumption is considered.Considerable finite element simulations are carried out to find the stresses at the disk center concerning the material orientation and the two dimensionless parameters.Also,an approximate formula obtained from analytical results,previously proposed in the literature for solving the tensile and compressive stresses at the disk center,is re-written and simplified based on these new definitions.The results of the approximate formula fitted to the analytical results are compared to those obtained from numerical solutions,suggesting a good agreement between the numerical and analytical methods.An approximate equation for the shear stress at the disk center is also formulated based on the numerical results.Finally,the influence of the assumptions for simplification of the proposed formula for the tensile,compressive,and shear stresses at the disk center is discussed,and simple and practical equations are proposed as estimations for the stresses at the center of the BD specimen for low to moderate anisotropic rocks.For highly anisotropic rocks,the reference plots can be used for more accuracy.

Correction of dynamic Brazilian disc tensile strength of rocks under preloading conditions considering the overload phenomenon and invoking the Griffith criterion

Dynamic tensile failure is a common phenomenon in deep rock practices,and thus accurately evaluating the dynamic tensile responses of rocks under triaxial pressures is of great significance.The Brazilian disc(BD)test is the suggested method by the International Society for Rock Mechanics and Rock Engineering(ISRM)for measuring both the static and dynamic tensile strengths of rock-like materials.However,due to the overload phenomenon and the complex preloading conditions,the dynamic tensile strengths of rocks measured by the BD tests tend to be overestimated.To address this issue,the dynamic BD tensile strength(BTS)of Fangshan marble(FM)under different preloading conditions were measured through a triaxial split Hopkinson pressure bar(SHPB).The fracture onset in BD specimen was captured through a strain gage around the disc center.The discrepancy between the traditional tensile strength(TTS,determined by the peak load P_(f) of the BD specimen)and the nominal tensile strength(NTS,obtained from the load P_(i) when the diametral fracture commences in the tested BD specimen)was applied to quantitatively evaluating the overload phenomenon.The Griffith criterion was used to rectify the calculation of the tensile stress at the disc center under triaxial stress states.The results demonstrate that the overload ratio(s)increases with the loading rate(σ)and decreases with the hydrostatic pressure(σ_(s)).The TTS corrected by the Griffith criterion is independent of theσ_(s)due to the overload phenomenon,while the NTS corrected by the Griffith criterion is sensitive to both the andσ.Therefore,it is essential to modify the tensile stress in dynamic confined BD tests using both the overload correction and the Griffith criterion rectification to obtain the accurate dynamic BTS of rocks.

Brazilian Spotted Fever Mortality Profile: 2018 to 2022

Background: Spotted Fever (SF) is an acute febrile zoonosis of variable severity that typically occurs in an endemic manner with worldwide distribution. Considering that SF is a disease of significant public health importance, this study aims to identify the mortality profile due to SF in Brazil from 2018 to 2022. Methods: Quantitative and descriptive cross-sectional approach. Data were collected from Brazilian Spotted Fever (BSF) cases registered in the Notifiable Diseases Information System (SINAN-DATASUS) across all regions of Brazil. The data collected includes information on the following variables: year of symptom, evolution, sex, race, environment of infection, region of notification, and age group. Subsequently, the data was entered into Microsoft Excel to create tables and graphs. The chi-square test was then applied to statistically analyze the associations between qualitative variables. A modified Poisson regression model with robust variance was constructed to analyze the age group data and determine which categories had different probabilities of death. The results show the estimates obtained for prevalence ratios, as well as their respective confidence intervals and p-values. The statistical software SAS version 9.4 was used to perform the analysis and a significance level of 5% was considered. Results: From 2018 to 2022, a total of 1126 cases of BSF were reported. Out of these cases, 59.3% (668) were cured, 32.4% (364) resulted in death, 1.1% (13) died from other causes and 7.2% (81) had no recorded outcome. Regarding the region with the highest death rate, the Southeast region led with 99.45% (362) of cases, followed by the Northeast region with 0.45% (2). As for the age group, the majority (63.7%) fell between the ages of 20 and 59 years old. In terms of race/color, 52.7% of the population identified as white. Regarding the contamination environment, 39.3% were in leisure areas. The outcome of death by BSF showed statistically significant associations with sex (p-value = 0.03) and age group (p-value = 0.003). Conclusion: The profile of deaths from Brazilian Spotted Fever primarily affects individuals from the Southeast region of the country, particularly men, and whites aged 20 years or older being contaminated mainly in leisure environments. This study provides a detailed understanding of the pattern of BSP-related deaths, providing crucial information for public health authorities. These insights provide valuable support for formulating informed policies and effective BSP control and prevention strategies.

Comparative Analysis of Metals in Seafood from Rio Doce Coastal Areas and Regional Fish Markets

On November 5, 2015, the Fundão Dam breached (the “Event”), releasing water, tailings, dam construction material, and debris to downstream watercourses. Over 20 million cubic meters of fine particles from the tailings, as well as scoured soil and sediments, reached the Rio Doce estuary and surrounding marine area 17 days later. Fishing was banned by the Federal Court of Espírito Santo in February 2016. The fishing ban area included the coastal area near the mouth of the Rio Doce and seaward to a depth of 25 meters, south to Barra do Riacho, and north to Degredo Beach. In June 2019, the Brazilian health agency, Anvisa, published a risk assessment for fish consumption which recommended daily consumption limits for fish of 200 grams for adults and 50 grams for children for both continental and coastal areas of the Rio Doce basin. Comparative analyses were performed between metal concentrations in marine fish and crustaceans collected in the banned fishing area to reference areas and commercialized seafood markets along the Brazilian coast. The results reveal that metals detected in seafood tissue collected in the fishing ban area are not significantly different than other reference areas or from commercially available seafood. This result indicates that elevated metal concentrations in seafood are a regional problem, unrelated to the Event. Higher concentrations of metals in fish in reference areas outside of the fishing ban area as well as in commercial seafood markets demonstrates that the risk management approach of a localized fishing ban is ineffective for reducing risk to the population related to seafood consumption. .

香蕉14-3-3蛋白基因Ma-14-3-3d的克隆及序列分析(英文)

[Objective] The aim of the study is to clone and analyze the gene encoding 14-3-3 protein from banana. [Method] Combined with PCR amplification, RACE (rapid amplification of cDNA ends) technique was employed to clone 14-3-3 gene from banana; then the amplified sequence was sequenced and homologically analyzed. [Result] A new cDNA homologous with 14-3-3 protein genes were obtained by RT-PCR and RACE ( rapid amplification of cDNA ends ) approaches. The full length of this cDNA was 866 bp encoding 197 amino acids. Alignment of deduced amino acid sequence with those from other plants revealed that the cDNA shared high homology with 14-3-3 protein genes from other plants, and was designated as Musa acuminata 14-3-3 gene (Ma-14-3-3d). Phylogenetic analysis reveals that Ma-14-3-3d has closer genetic relationship with those from monocotyledon species than those from other species. [Conclusion] Ma-14-3-3d belongs to the same lineage of 14-3-3 from monocotyledon.

香蕉柠檬酸合酶基因MaGCS的克隆及生物信息学分析

采用RACE-PCR的方法首次在香蕉中获得一个柠檬酸合酶基因的cDNA序列。经序列测定和Blastx比对分析表明,该cDNA全长1885bp,编码513个氨基酸残基,具有植物柠檬酸合酶基因的特征结构域,并与其他植物来源的乙醛酸循环体的柠檬酸合酶具有很高的序列相似性,将其命名为MaGCS(Musa glyoxysomal citrate synthase),并对其进行生物信息学分析,初步预测其理化性质及功能等。

香蕉果实的1个14-3-3蛋白同源基因的克隆及序列分析(简报)

根据在香蕉果实抑制缩减文库中获得的1个14-3-3蛋白基因片段,采用PCR和RACE相结合的方法从香蕉(Musaacuminate L. AAA group cv. Brazilian)cDNA文库中筛选到其全长cDNA序列。序列测定和Blastx比对分析结果表明,该cDNA全长1 037 bp,含有1个完整的阅读框,其编码区编码261个氨基酸残基,具有植物14-3-3蛋白基因的保守结构域,并与其他植物来源的14-3-3蛋白具有很高的同源性,将其命名为Ma-14-3-3b(Musa acuminate 14-3-3)。采用遗传进化系统发育树的分析结果表明,Ma-14-3-3b与来源于单子叶植物的多数14-3-3蛋白基因序列在同一个进化枝上。采用RT-PCR对其在香蕉果实发育不同时期的表达进行分析结果表明,在香蕉果实发育的不同时期差异表达,推测其可能在果实的发育中起作用。

Hazardous elements and amorphous nanoparticles in historical estuary coal mining area

In Brazil, intense coal exploitation activities have led to environmental deterioration, including soil mortification, water contamination, loss of ecosystem, and atmospheric contamination. In addition,considerable quantities of sulfur-rich residues are left behind in the mining area; these residues pose grave environmental issues as they undergo sulfide oxidation reactions. When sulfur oxides come in contact with water, extreme acid leachate is produced with great proportions of sulfate, and hazardous elements(HEs), which are identified as coal drainage(CMD). CMD is an environmental pollution challenge, particularly in countries with historic or active coal mines. To prevent CMD formation or its migration, the source must be controlled; however, this may not be feasible at many locations. In such scenarios, the mine water should be collected, treated, and discharged. In this study, data from 2005 to2010 was gathered on the geochemistry of 11 CMD discharges from ten different mines. There are several concerns and questions on the formation of nanominerals in mine acid drainage and on their reactions and interfaces. The detailed mineralogical and geochemical data presented in this paper were derived from previous studies on the coal mine areas in Brazil. Oxyhydroxides, sulfates, and nanoparticles in these areas possibly go through structural transformations depending on their size and formation conditions. The geochemistry of Fe-precipitates(such as jarosite, goethite, and hematite) existent in the CMD-generating coal areas and those that could be considered as a potential source of hazardous elements(HEs)(e.g., Cr) were also studied because these precipitates are relatively stable in extremely low pH conditions. To simplify and improve poorly ordered iron, strontium, and aluminum phase characterization, field emission scanning electron microscopy(FE-SEM), high-resolution transmission electron microscopy(HR-TEM), micro-Raman spectroscopy, and X-ray diffraction(XRD) and sequential extraction(SE) studies were executed on a set CMD samples from the Brazilian mines. This study aimed to investigate the role of both nanomineral and amorphous phase distribution throughout the reactive coal cleaning rejects profile and HEs removal from the water mine to provide holistic insights on the ecological risks posed by HEs, nanominerals, amorphous phases, and to assess sediments in complex environments such as estuaries.

Behaviour of layered sandstone under Brazilian test conditions:Layer orientation and shape effects

The experimental study in this paper focuses on the effects of the layer orientation and sample shape on failure strength and fracture pattern of samples tested under Brazilian test conditions(i.e.diametrical loading of cylindrical discs)for one particular layered sandstone which is from Modave in the south of Belgium.The variations of the strength in combination with the failure patterns are examined as a function of the inclination angle between the layer plane and the loading direction.The experimental,results clearly show that the induced fracture patterns are a combination of tensile and/or shear fractures.In shape effect experiments the layer thickness and the number of layer boundaries are investigated.Different blocks of Modave sandstone are used to prepare samples.The layer thickness is different among the various blocks,but the layer thickness in each studied rock block can be considered to be constant;hence,the number of layer boundaries changes according to the sample diameter for samples of the same block.The experimental study shows that the layer thickness plays a more important role than the number of layer boundaries per sample.

Particle flow study on strength and meso-mechanism of Brazilian splitting test for jointed rock mass

A discrete element method （DEM） called particle flow code （PFC2D） was used to construct a model for Brazilian disc splitting test in the present study. Based on the experimental results of intact Brazilian disc of rock-like material, a set of micro-parameters in PFC2D that reflected the macro-mechanical behavior of rock-like materials were obtained. And then PFC2D was used to simulate Brazilian splitting test for jointed rock mass specimens and specimen containing a central straight notch. The effect of joint angle and notch angle on the tensile strength and failure mode of jointed rock specimens was detailed analyzed. In order to reveal the meso-mechanical mechanism of crack coalescence, displacement trend lines were applied to analyze the displacement evolution during the crack initiation and propagation. The investigated conclusions can be described as follows. （1） The tensile strength of jointed rock mass disc specimen is dependent to the joint angle. As the joint angle increases, the tensile strength of jointed rock specimen takes on a nonlinear variance. （2） The tensile strength of jointed rock mass disc specimen containing a central straight notch distributes as a function of both joint angle and notch angle. （3） Three major failure modes, i.e., pure tensile failure, shear failure and mixed tension and shear failure mode are observed in jointed rock mass disc specimens under Brazilian test. （4） The notch angle roles on crack initiation and and joint angle play important propagation characteristics of jointed rock mass disc specimen containing a central straight notch under Brazilian test.

Mutual interference of layer plane and natural fracture in the failure behavior of shale and the mechanism investigation

Shale contains a certain amount of natural fractures,which affects the mechanical properties of shale.In this paper,a bonded-particle model in particle flow code(PFC)is established to simulate the failure process of layered shale under Brazilian tests,under the complex relationship between layer plane and natural fracture.First,a shale model without natural fractures is verified against the experimental results.Then,a natural fracture is embedded in the shale model,where the outcomes indicate that the layer plane angle(marked asα)and the angle(marked asβ)of embedded fracture prominently interfere the failure strength anisotropy and fracture pattern.Finally,sensitivity evaluations suggest that variable tensile/cohesion strength has a changeable influence on failure mechanism of shale,even for sameαor/andβ.To serve this work,the stimulated fractures are categorized into two patterns based on whether they relate to natural fracture or not.Meanwhile,four damage modes and the number of microcracks during the loading process are recognized quantitatively to study the mechanism of shale failure behavior.Considering the failure mechanism determines the outcome of hydraulic fracturing in shale,this work is supposed to provide a significant implication in theory for the engineering operation.

Dynamic rock tensile strengths of Laurentian granite: Experimental observation and micromechanical model

Tensile strength is an important material property for rocks. In applications where rocks are subjected to dynamic loads, the dynamic tensile strength is the controlling parameter. Similar to the study of static tensile strength, there are various methods proposed to measure the dynamic tensile strength of rocks.Here we examine dynamic tensile strength values of Laurentian granite(LG) measured from three methods: dynamic direct tension, dynamic Brazilian disc(BD) test, and dynamic semi-circular bending(SCB). We found that the dynamic tensile strength from direct tension has the lowest value, and the dynamic SCB gives the highest strength at a given loading rate. Because the dynamic direct tension measures the intrinsic rock tensile strength, it is thus necessary to reconcile the differences in strength values between the direct tension and the other two methods. We attribute the difference between the dynamic BD results and the direct tension results to the overload and internal friction in BD tests. The difference between the dynamic SCB results and the direct tension results can be understood by invoking the non-local failure theory. It is shown that, after appropriate corrections, the dynamic tensile strengths from the two other tests can be reduced to those from direct tension.

Stress-deformed state of cylindrical specimens during indirect tensile strength testing

In this study, the interaction between cylindrical specimen made ofhomogeneous, isotropic, and linearlyelastic material and loading jaws of any curvature is considered in the Brazilian test. It is assumed thatthe specimen is diametrically compressed by elliptic normal contact stresses. The frictional contactstresses between the specimen and platens are neglected. The analytical solution starts from the contactproblem of the loading jaws of any curvature and cylindrical specimen. The contact width, correspondingloading angle （2 ^0）, and elliptical stresses obtained through solution of the contact problems are used asboundary conditions for a cylindrical specimen. The problem of the theory of elasticity for a cylinder issolved using Muskhelishvili＇s method. In this method, the displacements and stresses are represented interms of two analytical functions of a complex variable. In the main approaches, the nonlinear interactionbetween the loading bearing blocks and the specimen as well as the curvature of their surfacesand the elastic parameters of their materials are taken into account. Numerical examples are solved usingMATLAB to demonstrate the influence of deformability, curvature of the specimen and platens on thedistribution of the normal contact stresses as well as on the tensile and compressive stresses actingacross the loaded diameter. Derived equations also allow calculating the modulus of elasticity, totaldeformation modulus and creep parameters of the specimen material based on the experimental data ofradial contraction of the specimen.