Carlos Alexandre Braz de Carvalho

Estudo da durabilidade de misturas solo-RBI grade 81 com vistas à aplicação em estradas florestais e camadas de pavimentos convencionais

This paper addresses the characterization of three soil-RBI Grade 81 mixtures for road engineering applications using laboratory testing data from wetting and drying durability tests. One mature (soil 1) and two young (soils 2 and 3) gneiss residual soils from the Zona da Mata Norte de Minas Gerais, Brazil, were used throughout the study. The laboratory testing program comprised the following steps: (i) RBI Grade 81 content: 6% regarding soil dry mass; (ii) compaction efforts: Standard, Intermediate and Modified Proctor; (iii) mixture specimens curing time: 7 days in acclimatized room. The testing program data supported that: (i) only tested mixtures of soils 1 and 3 compacted at the Intermediate compaction effort, and of soils 2 and 3 compacted at the Modified compaction effort endured all cycles in the durability test; (ii) mixture specimens of soil 3 compacted at the Modified Proctor compaction effort presented lower mass losses in the durability test (under 13%); (iii) from durability testing data standpoint, soil-RBI Grade 81 mixtures are regarded as potential road engineering materials.

Estudos laboratoriais do comportamento de um soloresidual arenoso reforçado com fibras de polipropileno, visando à aplicação em Estradas Florestais

Este trabalho teve como objetivo analisar o comportamento mecânico da mistura de um solo residual jovem de textura predominantemente arenosa reforcado com fibras de polipropileno, com vistas a aplicacao em estradas florestais. Como ponto de partida, determinou-se, mediante os resultados de ensaios de compressao nao-confinada, realizados em corpos-de-prova compactados na energia do ensaio Proctor Normal, que o quantitativo de 0,75% de fibras com 20 mm de comprimento foi a combinacao responsavel pelo maior ganho de resistencia. Com a mistura solo-fibra composta por essa combinacao, foram realizados ensaios triaxiais do tipo CID/Sat em corpos-de-prova compactados na energia anteriormente referida. Atraves desta pesquisa, foi possivel avaliar: (i) a influencia da variacao da umidade nos parâmetros de resistencia mecânica do solo e das misturas solo-fibra e (ii) a influencia das fibras nos parâmetros de resistencia ao cisalhamento do solo em estudo. Analisando os resultados, pode-se concluir que o uso de fibras de polipropileno promoveu um ganho da ordem de 110% na resistencia a compressao nao-confinada e de 560% na coesao de intercepto do solo estudado.

Durabilidade de solos estabilizados quimicamente com vistas á aplicação em estradas florestais

This paper addresses the assessment of the durability properties of mixtures of two soils using laboratory wetting and drying durability tests for forest road applications, as follows: (a) soils stabilization with the industrial waste grits; (b) soil improvement using lime or cement; (c) soil stabilization using grits, and soil mixture improvement using lime or cement. A mature and a young residual soil from the Zona da Mata Norte of Minas Gerais were used throughout the study. The laboratory testing program comprised the following steps: (a) grits content of 24 % in relation to soil dry mass; (ii) lime or cement contents of 10 % and 20 % in relation to grits dry mass; (c) specimens compacted at the standard and modified Proctor effort; (d) mixture specimens curing time of seven days in acclimatized room. The testing program data supported that: (a) the soil -lime, soil-cement, soil-grits-lime and soil-grits-cement mixtures endured all cycles in the durability test; (b) the mixtures of soil 1, grits and lime compacted at the modified Proctor effort presented the best mechanical response in the durability tests, showing losses of approximately 7 %; regarding soil 2 mixtures, the best result was related to the grits and cement mixtures compacted at the modified Proctor effort, showing losses of approximately 9 %; (c) as for durability standard requirements, the mixtures of soil-grits presented potential for road engineering applications only in association with lime or cement.

Influência do tráfego de veículos comerciais em rodovias vicinais não pavimentadas: estudo de caso aplicado à VCS 346, Viçosa, MG

This paper approaches the influence of the variation of load per axle and tire pressure on the recoverable superficial deflections in a pavement structure of the VCS 346 unpaved road taken as representative of the secondary road net of Vicosa-MG, Brazil. The program of study considered the following analysis: (i) traffic volume counting including 2C type commercial vehicles; (ii) predicted recoverable superficial deflections in function of the available data from the study; (iii) structure of the pavement including data from the materials of its layers. By the analyses, it was verified that the application of more critical loading levels affected significantly the pavement serviceable life and depending on the combination of axle load and tire pressure, road pavement serviceable life could be reduced by 89%. In this study, it was also investigated the application of two methods to measure sub-grade reinforcement layer thickness of unpaved roads. One of these two methods was empirical, the DNITs Flexible Pavement Design criteria and the other was based on elastic theory applied to a two layer system. The use of the elastic theory was more adequate to measure unpaved roads improved with wearing courses (two layer system) proved to be the best procedure for designing unpaved road systems.

Avaliação do subleito de rodovias vicinais de baixo volume de tráfego por meio de ensaios geotécnicos

This paper approaches the technical feasibility of using local soils, preferably those of lateritic geotechnical behavior, in subgrade reinforcement layers of low traffic volume vicinal roads through geotechnical testing and MCT methodology (Miniature, Compacted, Tropical). Therefore, disturbed soil samples were collected from the road subgrade VCS 493 and VCS 296 from to the vicinal road net of the city of Vicosa, Minas Gerais state, Brazil. The laboratory study program included the following trials: (i) grain-size distribution; (ii) Atterberg limits (LL and PL); (iii) specific mass of soil grain; (iv) compaction and CBR carried out in normal Proctor energy; (v) mini-MCV compaction; and (vi) specimen weight loss by water immersion. By using the results from this, it was possible to check if soils presenting lateritic behavior were classified in the LGgroup of the MCT methodology, and that they even presenting high values of liquid limit and plasticity index, when compacted in normal Proctor energy and therefore water immersed, they did not present expansion with a significant value in CBR trial. On the other hand, the saprolitic sands presented mass loss by water immersion (Pi) difficult to be predicted through the MCT methodology because they can present very high and low values according to compacteness reached during compaction process, as it can be noted in the result from sample 8.

Avaliação do potencial do grits como material de construção na produção de tijolos de solo-cimento

Grits is a solid residue, with sandy characteristics and grayish appearance, produced by the kraft pulp industry, during the recovery stage of white liquor used in the cooking of the wood chips. The aim of this paper was to study the potential of grits as a building material, considering their employability in the manufacturing of soil-cement blocks. To set the ideal amount of residue to be used, the traits in volume 1:14:0; 1:10,5:3,5; 1:7:7; 1:3,5:10,5; 1:0:14 of cement, soil and grits were studied, respectively. The materials were characterized by the sieve analysis, liquid limit and plastic limit tests and the results are consistent with the prescriptive requirements. The practical test of the box was also used to verify the materials and the results met the recommendations. Once the compaction test was performed to obtain the optimum moisture content, the bricks were produced with 90% of this value, because the compressive strength is increased with dry material. However, it was not possible to produce blocks with traits 1:3,5:10,5 and 1:0:14 because, in these cases, mixtures of soil-cement-grits did not show sufficient plasticity. The blocks produced with others

Aplicações de misturas solo-"grits" em estradas florestais: resistência mecânica via CBR

This paper is directed to forest road engineering applications, and address the potentialities of using an industrial solid waste from the cellulose industry, named grits, in the stabilization process of two soils from Zona da Mata Norte of Minas Gerais States, Brazil. Soil types tested comprised a mature residual silty-sandy-clay and a young residual clayey-silty-sand. Soil-grits mixtures were prepared at 4, 8, 12, 16, 20, 24 and 28 % stabilizer contents referred to soil dry masses. Mechanical strength and swelling parameters were determined by CBR (California Bearing Ratio) tests. The laboratory testing program data supported that addition of grits to soils led to: (i) significant mechanical strength gains that could be better associated with the clayey-silty-sandy soil; (ii) increases and decreases in swelling with increases in grits contents referred to the silty-sandy-clayey and the clayey-silty-sandy soils respectively, and (iii) increase in compaction effort did not lead to better mechanical responses of the mixtures regarding CBR and swellingCBR.

Uso de resíduos em pavimentos de estradas florestais: caracterização de solos e misturas solo-grits

This paper addresses data from a research program in development on engineering properties of soil-chemical stabilizer mixtures for forest road application. Soil samples from sandy and clayey soils from the Zona da Mata Norte of Minas Gerais, Brazil, stabilized with grits (waste from cellulose industries) were used throughout the study. The laboratory-testing program comprised the following geotechnical tests: sieve analysis, density of solid particles, Atterberg limits and compaction. Data supported the good behavior of waste as stabilizer agent changing significantly soil plasticity and compaction parameters.

Correção granulométrica de solos para aplicações em estradas florestais: estudo de caso com solos da CENIBRA

This paper presents a procedure for studying the mechanical behavior of three soils from the cellulose company CENIBRA S. A. located in the city of Belo Oriente, the state of Minas Gerais, Brazil, to be used as a surface course, sub-grade reinforcing layer and sub-base on forest roads. The mechanical stabilization technique named textural proportioning was used throughout the study. The laboratory testing program encompassed the use of different amounts of soils in order to determine the most efficient combination of two of them to be used in the CENIBRA S. A. forest road system. Soil mixtures were produced using sand contents of 60, 70 and 80% and clayey soils contents of 20, 30 and 40%. Soils and mixtures specimens were compacted at the modified Proctor compaction effort. The best mechanical response was associated to the 80% sand and 20% yellow clay mixture, which presented bearing capacity via ISC of 63%.

Sistemas de classificações geotécnicas de solos: estudo de caso aplicado à rodovia não pavimentada vcs 346, Viçosa, MG

RESUMO – Este artigo aborda uma contribuicao as classificacoes geotecnicas tradicionais de solos Unified Soil Classification System (USC), Transportation Research Board System (TRB) e a Metodologia Miniatura, Compactado, Tropical (MCT) para um caso aplicado a rodovia municipal nao pavimentada VCS 346, no Municipio de Vicosa, MG, considerando-se varias amostras deformadas de solos coletadas no subleito da referida via. Os principais objetivos deste estudo residem na contribuicao de um banco de dados geotecnicos sobre classificacoes de solos tropicais, bem como na verificacao de possiveis agrupamentos entre os sistemas geotecnicos tradicionais de classificacao e a metodologia MCT. O programa de laboratorio envolveu a realizacao dos seguintes ensaios: (i) granulometria conjunta; (ii) limites de Atterberg (LL e LP); (iii) massa especifica dos graos do solo; (iv) compactacao Mini-MCV; e (v) perda de massa do corpo-de-prova por imersao em agua. Os resultados possibilitaram verificar que, apos a classificacao das amostras, varios agrupamentos entre os sistemas de classificacoes geotecnicas tradicionais coincidiram com aqueles ja apresentados na metodologia MCT e, considerando a pedogenese da regiao de Vicosa, MG, para o grupo NG’, houve a contribuicao dos grupos SC, SM e CL do Sistema USC e do grupo A-4 do Sistema TRB.