Compaction of soil-grits mixtures for use in forestry road : influence of time between mixture and compaction on mechanical strength

Vários fatores influenciam a execução e a "performance" de camadas de pavimentos rodoviários constituídas de solos estabilizados quimicamente, com destaque para a homogeneização da mistura e o período de tempo decorrido entre a mistura e a compactação, bem como para a escolha do equipamento de compactação. Aborda-se, no presente artigo, a influência do tempo decorrido entre a mistura e a compactação (TMC) nos parâmetros de compactação e na resistência mecânica de misturas de dois solos típicos da Zona da Mata Norte de Minas Gerais, com o resíduo da indústria de celulose denominado "grits", com vistas à sua aplicação em estradas florestais. Analisa-se, também, a influência de diferentes lotes desse resíduo na resistência mecânica das misturas. Trabalhou-se com os resultados de ensaios de índice de suporte Califórnia (ISC ou CBR) realizados em corpos-de-prova de misturas moldados na energia de compactação do ensaio Proctor Intermediário. Os resultados permitem concluir que o tempo decorrido entre mistura e compactação influencia significativamente a resistência mecânica das misturas analisadas, recomendando-se, para fins práticos, que estudos dessa natureza devam ser feitos em bases regionais de ocorrência de solos. Observou-se, também, influência significativa do lote na resistência mecânica das misturas. _______________________________________________________________________________ ABSTRACTMany factors affect the construction and performance of chemically stabilized highway pavement soil layers, especially mixture homogenization, time between mixture and compaction, and selection of compaction equipment. Regarding forest road application, this paper addresses the influence of time between mixture and compaction (TMC) on compaction optimum parameters and on mechanical strength of mixtures of two typical soils from the region ‘Zona da Mata Norte’, State of Minas Gerais, and grits, a waste from the cellulose industry, as well as the influence of grits sampling on the mechanical strength of soil 2-grits mixtures. California bearing ratio (CBR) data from laboratory specimens compacted at the Intermediate Proctor compaction effort were used throughout the study. The laboratory testing data supported that time between mixture and compaction significantly affected the mechanical strength of the tested soil mixtures. Regarding soil samples and from a practical point of view, it is recommended that such studies should be always performed on regional basis. It was observed significant influence of grits sampling on the mechanical strength of soil 2-grits mixtures

Systems engineering: availability and reliability

Current trends in Industry 4 [...

Use of industrial grits in forest road pavements : influence of curing times on the mechanical strength and swelling of compacted soil-grits mixtures

Analisou-se a influência do teor de estabilizante, da energia de compactação e do período de cura na resistência mecânica e expansão de dois solos da Zona da Mata Norte de Minas Gerais. As amostras de solos residuais de gnaisse coletadas na cidade de Viçosa, MG, Brasil, respectivamente, de texturas argilo-arenosiltosa e areno-argilo-siltosa, foram denominadas solos 1 e 2. Empregou-se como estabilizante químico o resíduo “grits” fornecido pela empresa de Celulose Nipo Brasileira (CENIBRA); os teores, em massa, de 4, 8, 12, 16, 20, 24 e 28% desse resíduo foram utilizados nas misturas solo-“grits”. Corpos-de-prova das misturas solo- “grits” foram compactados nos teores ótimos de umidade relativos às energias de compactação dos ensaios Proctor intermediário e modificado e curados por 0, 7, 28 e 90 dias. Avaliou-se a resistência mecânica dos solos e misturas através dos seguintes parâmetros: (a) índice de suporte Califórnia (ISC ou CBR), resistência à compressão não confinada (RCNC) e resistência à tração em compressão diametral (Rt). Os resultados permitiram concluir que todos os parâmetros considerados na análise influenciaram, significativamente, a resistência mecânica das misturas solo-“grits”, sendo o comportamento das misturas solo 1-“grits” influenciado, também, pelo teor de sódio presente na constituição química do “grits”. ____________________________________________________________________________________ ABSTRACTThis paper addresses the influence of stabilizer content, compaction effort and curing time on the mechanical strength and swelling of two soils from the “Zona da Mata Norte” region, State of Minas Gerais, Brazil. Two residual gneiss soils from the municipality of Viçosa, Brazil, silt-sand-clay and silt-claysandy soils named soils 1 and 2, respectively, were used in this study. Industrial grits provided by Celulose Nipo Brasileira - CENIBRA was used as stabilizer, with contents ranging from 4 to 28 % regarding soil dry mass. Specimens of soil-grits mixtures were compacted at the Intermediate Proctor compaction effort and curing times of 0, 7, 28 and 90 days. Mechanical strength was evaluated as follows: California bearing ratio (CBR), unconfined compression strength (UCS) and indirect tensile strength (ITS). Data from the laboratorytesting program supported that all parameters affected mixture mechanical strength significantly, and the mechanical behavior of soil 1-grits mixtures were also influenced by sodium content of grits

Utilização do resíduo sólido industrial (lama-de-cal) em pavimentos de estradas florestais

O objetivo do presente estudo foi avaliar os efeitos do resíduo sólido industrial (lama-de-cal) nas propriedades geotécnicas de amostras de solo da região de Alagoinhas, BA, Brasil. Das sete amostras coletadas, apenas duas foram selecionadas, por apresentar maior potencial geotécnico. Utilizaram-se ensaios de caracterização, CBR e permeabilidade, cujos resultados indicaram que a amostra de solo denominada good gravel quando estabilizada com lama-de-cal, na dosagem de 20 e 25%, foi a mais promissora. ____________________________________________________________________________________ ABSTRACTThe objective of the present study was to evaluate the effects of industrial solid waste (whitewash mud) on geotechnical properties considering the following engineering parameters: California Bearing Ratio (CBR), Atterberg limits and Permeability test. Seven soil samples derived from Alagoinhas, Bahia - Brazil, were classified by the Transportation Research Board (TRB) system. Two were selected as having a great geotecnical potential classified as A-3 (0) and A-2-4 (0), whitewash mud contents 10%, 15%, 20% and 25% dry weight and medium compaction effort were studied in the laboratory testing program. The results indicated the soil denominated good gravel as being the most promising one, when stabilized with whitewash mud, reaching the best results with the dosage of 20 and 25% of whitewash mud

Mudança da Cultura Docente em um Contexto de Trabalho Colaborativo de Introdução das Tecnologias de Informação e Comunicação na Prática Escolar

This study investigates indications of change in the teaching practice and development in a public school where math teachers, together with an external agent, formed a collaborative group aiming at introducing communication and information technologies in the pedagogical practice. The case of a participant teacher who was interviewed after being observed during her classroom teaching practice and during the group meetings is reported. The study shows that the use of communication and information technologies for teaching mathematics set in motion a catalyzing process in the teacher’s professional development and changed her teaching methodology. In this scenario, an interactive teacher emerged, willing to share her experiences with co-workers through the use of communication and information technologies. In this way, she can keep up with the improvements in her professional field and lead her students to access information available on the web. Keywords: Teaching Culture. Communication and Information Technology. Teaching Development. Collaborative Work.Este estudo investiga indícios de mudança da cultura e desenvolvimento docente numa escola pública, em um contexto no qual professores de matemática da escola e um agente externo formaram um grupo colaborativo visando introduzir as tecnologias de informação e comunicação (TIC) na prática pedagógica. Aborda-se o caso de uma professora participante que foi entrevistada e observada em sua prática docente e nos encontros do grupo. O estudo mostra que a utilização das TIC no ensino de Matemática, mediado pela colaboração, desencadeou um processo catalisador do desenvolvimento profissional da professora e de mudanças na cultura de seu trabalho docente. Emergiu, neste cenário, uma professora interativa, que vê ampliada, com as TIC, a possibilidade de compartilhar experiências e saberes com outros docentes, podendo, assim, acompanhar o desenvolvimento de seu campo profissional e também levar seus alunos a terem acesso e interlocução com os saberes disponíveis na Web. Palavras-Chave: Cultura Docente. Tecnologias de Informação e Comunicação. Desenvolvimento Docente. Trabalho Colaborativo

Generating human-like movements on an anthropomorphic robot using an interior point method

In previous work we have presented a model for generating human-like arm and hand movements on an anthropomorphic robot involved in human-robot collaboration tasks. This model was inspired by the Posture-Based Motion-Planning Model of human movements. Numerical results and simulations for reach-to-grasp movements with two different grip types have been presented previously. In this paper we extend our model in order to address the generation of more complex movement sequences which are challenged by scenarios cluttered with obstacles. The numerical results were obtained using the IPOPT solver, which was integrated in our MATLAB simulator of an anthropomorphic robot.EU funded Project PF7 Marie Curie ``NETT - Neural Engineering Transformative Technologies'', by FEDER funds through COMPETE (Operational Programme Thematic Factors of Competitiveness) and by portuguese funds through FCT (Foundation for Science and Technology) within the projects PEst-C/MAT/UI0013/2011 and FCOMP-01-0124-FEDER-022674

Exercise improves long-term social and behavioral rhythms in older adults: did it play a role during the COVID-19 lockdown?

The study aimed to verify whether exercise training in older adults can improve social behavioral rhythms (SBR) and if any modification is maintained over time. Older adults (n=120) from a previous randomized controlled trial, were randomly allocated to either a moderate-intensity exercise group or a control group. SBR was evaluated at t0, t26, and t48 weeks (during the COVID-19 lockdown), using the brief social rhythms scale (BSRS). Seventy-nine participants completed the follow-up (age 72.3±4.7, women 55.3%). An improvement in the BSRS score was found in the exercise group at 26 weeks (p=0.035) when the exercise program was concluded, and it was maintained at 48 weeks (p=0.013). No improvements were observed in the control group. To conclude, SBR, previously found as a resilience factor in older adults during COVID-19, appear to improve after a moderate 12 weeks exercise program, and the improvement persisted even after stopping exercise during the COVID-19 lockdown

Exercise Improves the Impact of Chronic Pain in Older Adults: Results of an RCT

Background: Chronic Pain (CP) is a crucial determinant for disability in older adults. CP amplifies the impact of other common age-related diseases and increases cardiovascular risk. Physical exercise can improve CP. Randomized Controlled Trials (RCTs) with high-intensity exercise in older adults excluded people with Moderate Chronic Illness (MCI) and CP. Objective: This study aimed at evaluating in an RCT whether moderate exercise training can improve chronic pain in a sample of older adults, including people with MCI, and if any modification persists over time. Methods: A sample of 120 older adults was randomly selected for a moderate-intensity exercise program or cultural activities (control group). Chronic pain was assessed at t0, at t12 (end of the trial), and t48 weeks, by means of the Italian version of the SIP-Roland Scale. Results: Seventy-nine participants completed the follow-up (age 72.3±4.7, women 55.3%). At the end of RCT, an improvement in the SIP scale score was found in the exercise group (p=0.035), showing a lower score than the control group; this difference was not maintained at 48 weeks (p=0.235). Conclusion: Our study highlighted that a moderate-intensity exercise intervention reduced chronic pain in older adults, but this effect disappeared at follow-up after 36 weeks from the end of the training program. These findings suggested that such kinds of programs, easily accessible to old people even with MCI, should be implemented and supported over time, thus promoting active aging and preventing CP of age-related diseases. Clinical Trial Registration: Clinical.Trials.gov.NCT03858114