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6. A multi-stage cyclic queueing model.

Author

Maher, M. J. and Cabrera, J. G.

Subjects
PRODUCTION engineering, PRODUCTION scheduling, COST control, QUEUING theory, STOCHASTIC processes, INDUSTRIAL costs, COST effectiveness
Abstract

This paper analyses a multi-stage cyclic queueing system in which there are alternate service and transit stages. The service times are negative exponentially distributed, but it is shown that the transit time distributions may be any of a whole range of types, from constant to negative exponential. It is also shown that the production rate of the system does not depend on the individual mean transit times, but only on the sum of these mean transit times. An explicit expression for the average production rate is derived and used in two examples, (i) a two-stage earthmoving project, and (ii) a four-stage asphalt paving project, to obtain regions of optimal haul fleet size, in the parameter space, so as to minimize the cost of the system. [ABSTRACT FROM AUTHOR]

Published
1975
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9. Interfacial effects on stress transfer in fiber-reinforced composites

Author

Wu, Z J, Ye, J Q, Cabrera, J G, Wu, Z J, Ye, J Q, and Cabrera, J G

Abstract

A three-dimensional solution for a fiber-reinforced circular cylinder is presented for axisymmetric force and displacement boundary conditions. The solution, which can satisfy all the boundary conditions prescribed on the curved and end surfaces of the cylinder, can be used directly in the micromechanical analysis of fiber-reinforced composites to investigate the typical representative volume element (RVE). The element consists of a combined circular cylinder composed of a solid inner circular cylinder of transversely isotropic fiber, a concentric enter circular cylinder of isotropic matrix material, and an interface layer between the fiber and the matrix. The radial and tangential flexural compliances of the interfacial material are considered, and their effects on the stress transfer at the interface are studied parametrically. The numerical results presented show that the material properties of the interfacial layer have significant influences on the stress distribution within the RVE, particularly at the cross sections near the ends of the cylinder, where external loads are applied.

Published
2000

10. 3D analysis of stress transfer in the micromechanics of fiber reinforced composites by using an eigen-function expansion method

Author

Wu, Z J, Ye, J Q, Cabrera, J G, Wu, Z J, Ye, J Q, and Cabrera, J G

Abstract

This paper presents an exact solution for an inhomogeneous, transversely isotropic, elastic circular cylinder subjected to axisymmetric force and displacement boundary conditions. The solution is obtained on the basis of an eigen-function expansion method and can satisfy all the boundary conditions prescribed on the curved and end surfaces of the cylinder. It can be used directly in the micromechanical analysis of fiber reinforced composites to investigate the typical Representative Volume Element (RVE). The element consists of a combined circular cylinder composed of a solid inner circular cylinder of transversely isotropic fiber and a concentric outer circular cylinder of isotropic matrix material. Using this solution, all the stress and displacement components of both the inner fiber and the outer matrix, and hence the stress transfer in the interface between the fiber and matrix, are expressed analytically. The numerical results presented show that stress concentration occurs near the ends of the cylinder where external forces are applied.

Published
2000

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Author

Cabrera, J. G. and Cabrera, J. G.

Abstract

High-viscosity bitumen blended with Styrene Butadiene Copolymer (SBS) and fibers is used, of late, for drainage pavement, for the purpose to prevent cracking and rutting, as well as to prevent flow carrying bituminous mixtures. However, it was not impossible to evaluate whether, or not, the mechanical properties and durability of such bitumens are suitable, at both extremes of low or high temperatures. The authors, therefore, have developed a method for determining the mechanical properties of these bitumens, using some new tests, such as the Improved Fraass Breaking Point (IFBP) Test, the Moriyoshi Breaking Point (MBP) Test, the High-Temperature Long-Time Durability (HTLTD) Test and the Bending Test. The method employed for measuring viscosity at high temperature was the Flow Test by rheometer. This paper describes the various results of tests for high-viscosity bitumens blended with the SBS and fibers. The authors obtained some brittle points and mechanical properties of these bitumens by using the said testers. The authors found the fracture properties and durability of bitumen blended with various fibers unfavorable, compared with the original bitumens.

Published
1999

19. Interfacial Effects on Stress Transfer in Fiber-Reinforced Composites.

Author

Wu, Z. J., Ye, J. Q., and Cabrera, J. G.

Subjects
STRAINS & stresses (Mechanics), FIBROUS composites, MEASUREMENT
Abstract

A three-dimensional solution for a fiber-reinforced circular cylinder is presented for axisymmetric force and displacement boundary conditions. The solution, which can satisfy all the boundary conditions prescribed on the curved and end surfaces of the cylinder, can be used directly in the micromechanical analysis of fiber-reinforced composites to investigate the typical representative volume element (RVE). The element consists of a combined circular cylinder composed of a solid inner circular cylinder of transversely isotropic fiber, a concentric outer circular cylinder of isotropic matrix material, and an interface layer between the fiber and the matrix. The radial and tangential flexural compliances of the interfacial material are considered, and their effects on the stress transfer at the interface are studied parametrically. The numerical results presented show that the material properties of the interfacial layer have significant influences on the stress distribution within the RVE, particularly at the cross sections near the ends of the cylinder, where external loads are applied. [ABSTRACT FROM AUTHOR]

Published
2000
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25. An assessment of concrete curing efficiency using gas permeability

Author

Wainwright, P. J., Cabrera, J. G., and Gowripalan, N.

Abstract

The current practice of assessing the efectiveness of a concrete curing compound is based on evaporation measurements from cement mortar slabs. The lack of precision of individual moisture loss measurements has prompted further investigation to measure other parameters to assess curing eficiency. This Paper reports preliminary results of a method based on oxygen permeability to assess curing eficiency. A comparison is made with results obtained using the method recommended in a British Standard draft.3 The oxygen permeability method can also be applied to traditional methods of curing such as those utilizing wet hessian or burlap.

Published
1989
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27. A new gas permeameter for measuring the permeability of mortar and concrete

Author

Lynsdale, C. J. and Cabrera, J. G.

Abstract

Synopsis A permeability cell for measuring the permeability of mortar and concrete to gas is described. The problems encountered and overcome during the development of the cell are discussed. The cell is designed to test 25 mm diameter mortar samples but can also be used for 50mm diameter concrete specimens. Specimens of heights between 10 and 50mm can be tested. Measurements using the new cell are highly repeatable and reproducible. The cell is very sensitive to the influence of water/cement ratio, age and replacement of cement by pulverized-fuel ash. It can be used to obtain permeability profiles through the depth of a concrete element in order to evaluate the influence of different curing conditions or curing compounds.

Published
1988
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31. The mechanism and rate of attack of sodium sulphate solution on cement and cement/pfa pastes

Author

Plowman, C. and Cabrera, J. G.

Abstract

Synopsis A study of the mechanisms and rates of attack of a sodium sulphate solution on four ordinary Portland cement (OPC) pastes, and four OPC/pfa pastes is presented. Accelerated experiments were carried out on mortar cubes, and samples from different depths were analysed by X-ray spectrometry and X-ray diffraction. The mechanism of attack was similar for the different cements: initial attack on the hydrated calcium aluminates produced AFt and AFm phases, and subsequent attack on calcium hydroxide resulted in the formation of gypsum. Incorporation ofpfa reduced the rate of attack, due to the finer pore size distribution of the paste, and the formation of Afm in preference to Aft. Subsequent attack on calcium hydroxide was greatly reduced.

Published
1988
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32. Experimental techniques for studying hydration reactions of calcium aluminates

Author

Plowman, C. and Cabrera, J. G.

Abstract

Synopsis Methods are described for studying the hydration reactions of calcium aluminates extracted from cement clinkers. The extraction method uses a maleic acid/methanol treatment, followed by aqueous ammonium chloride. Hydration time is controlled by stopping the hydration reaction by immersing the specimen in cold nitrogen vapour. Early-age morphological data are obtained by scanning electron microscopy, and the reaction rate is quantified by an X-ray diffraction procedure, provided that atmospheric carbon dioxide is excluded from the sample.

Published
1988
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33. The process and mechanism of alkali — silica reaction using fused silica as the reactive aggregate

Author

Cabrera, J. G., Wilson, M., and Zou, Y.

Abstract

As part of a detailed study to investigate the processes and mechanism of alkali—silica reaction (ASR), OPC mortars with 50% of the aggregate replaced by highly reactive fused silica (FS) were immersed in 1M KOH and saturated NaCl solutions at 38°C for 150 days. The expansion of the mortars was measured every 5 days for the first 30 days and every 15 days thereafter, and compared with the expansion of a series of OPC control mortars without FS. Maximum expansions (up to 2·2%) were observed in the FS mortars immersed in NaCl. Polished mortar specimens were studied using back-scattered electron imaging techniques and electron microprobe analysis to determine the extent of reaction of the FS and to obtain quantitative chemical analyses of the ASR gels. ASRfrequently appeared to initiate inside the reactive silica grains rather than at their peripheries, possibly reflecting the higher surface energies of microcracks and other internal discontinuities. The amount of visible reaction of the FS appeared greater in the KOH mortars, although they expanded less than the NaCl mortars. Element mapping of partially reacted FS grains demonstrated that alkali cations (Na+, K+) are clearly capable of diffusing into the silica structure, whereas the larger hydrated Ca2+ ions are not. The ASR gels generated in the NaCl mortars had low CaO contents &lt; 1 wt%) compared with those produced in the KOH solution (∼14·5 wt%). This appears to provide conclusive evidence that high calcium contents inhibit the expansion of ASR gels. The implications of these experimental results for elucidation of the mechanism of ASR are discussed. The importance of absorption of alkali cations (Na+, K+) onto the surface of the reactive aggregate during the early stages of reaction and the availability of Ca2+ ions in the cement pore fluids in controlling the expansion behaviour of the resultant ASR gels are stressed.As part of a detailed study to investigate the processes and mechanism of alkali—silica reaction (ASR), OPC mortars with 50% of the aggregate replaced by highly reactive fused silica (FS) were immersed in 1M KOH and saturated NaCl solutions at 38°C for 150 days. The expansion of the mortars was measured every 5 days for the first 30 days and every 15 days thereafter, and compared with the expansion of a series of OPC control mortars without FS. Maximum expansions (up to 2·2%) were observed in the FS mortars immersed in NaCl. Polished mortar specimens were studied using back-scattered electron imaging techniques and electron microprobe analysis to determine the extent of reaction of the FS and to obtain quantitative chemical analyses of the ASR gels. ASRfrequently appeared to initiate inside the reactive silica grains rather than at their peripheries, possibly reflecting the higher surface energies of microcracks and other internal discontinuities. The amount of visible reaction of the FS appeared greater in the KOH mortars, although they expanded less than the NaCl mortars. Element mapping of partially reacted FS grains demonstrated that alkali cations (Na+, K+) are clearly capable of diffusing into the silica structure, whereas the larger hydrated Ca2+ions are not. The ASR gels generated in the NaCl mortars had low CaO contents < 1 wt%) compared with those produced in the KOH solution (∼14·5 wt%). This appears to provide conclusive evidence that high calcium contents inhibit the expansion of ASR gels. The implications of these experimental results for elucidation of the mechanism of ASR are discussed. The importance of absorption of alkali cations (Na+, K+) onto the surface of the reactive aggregate during the early stages of reaction and the availability of Ca2+ions in the cement pore fluids in controlling the expansion behaviour of the resultant ASR gels are stressed.

Published
1994
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41. The relationship between porosity and thermal conductivity of concrete

Author

Ganjian, Esmaiel, Cabrera, J. G., and Tinker, J. A.

Subjects
620.13696
Abstract

This thesis reports the details and results of an experimental study into the effect of porosity on the thermal conductivity of lightweight and normal-weight concretes. The concretes were made from either Pellite, limestone or quartzitic coarse aggregates, with or without air-entraining agent. Their density varied from 1550 to 2350 kg/m3 and their porosity from 10 to 39 per cent. The thermal conductivity of all the concretes was measured in accordance with B.S. 874: 1988, using a plain hot-plate technique and the total porosity and pore size distribution of each mix were determined using vacuum saturation and Mercury Intrusion Porosimetry. Micromorphological changes were additionally assesed by: a) using thermal analysis methods to monitor lime and non-evaporable water content of mortars and also to monitor the carbonation process by quantitative evaluation on mortar samples. b) assessment of the depth of carbonation on concrete cubes. c) using Scanning Electron Microscopy on coarse aggregates and mortar samples. For characterization purposes, the experimental programme also involved studying the properties of fresh concrete, such as workability and air content and other engineering properties of hardened concretes, such as compressive strength. The results obtained from the individual tests were statistically analysed using a standard `Statistical Analysis System' (SAS) package. This enabled detailed examination of the relationship between the different properties to be assessed. Resulting from this, a model was developed which enabled the thermal cocductivity of a concrete to be estimated knowing its dry density, total porosity and median pore diameter. The findings of this investigation confirm that in general, the thermal conductivity of concretes are directly related to density and inversely related to porosity and pore diameter and that density and total porosity have the highest coefficient of correlation respectively.

Published
1990

42. Performance and Durability of Bituminous Materials

Author

Cabrera, J. G., Dixon, J. R., Cabrera, J. G., and Dixon, J. R.

Subjects
Bituminous materials--Evaluation--Congresses, Road materials--Evaluation--Congresses, Roads--Design and construction--Congresses, Pavements, Bituminous--Congresses
Abstract

This book covers new advances in materials and methods, particularly orientated towards the optimization of energy expenditure required for the preparation of aggregates, bituminous binders and bituminous mixtures and the implications which arise with regard to the European specifications and codes of practice.

Published
1996

43. The use of red tropical soils as pozzolanas : reactions, products and properties

Author

Nwakanma, Charles Amobi and Cabrera, J. G.

Subjects
624.15
Abstract

Nineteen red tropical soils from the States of Paraiba and Pernambuco which are located in the North East of Brazil were treated with high calcium lime, they reacted showing a wide range of variation of maximum unconfined compressive strengths with - 4.5% or 6.0% lime generally required to produce maximum strength. The reaction between the soil and lime is mainly a diffusion controlled process. Most of the reaction takes place within five to seven days and the reaction within this period obeys Jander's diffusion equation for solid state reactions. Based on the constant rate of reaction obtained from this equation and on the quantity of the reactive components of the soil, an activity index, Ai, is proposed and its validity tested against the unconfined compressive strength of the soil-lime system. A valid statistical correlation is presented linking Ai value with the empirical reactivity parameter of Thompson. Identification of the types of the reaction products by x-ray diffraction which is greatly aided by the use of a semiautomated computer search program reveals that the soils form cementitious reaction products varying from dense and close textured calcium silicates of the tobermorite-like type through alumino-silicates to calcium alumino-ferri-silicates with relatively larger voids when the soils are treated with lime and cured for two years at 22°C. The increase in strength of the soil-lime system not only depends on the volume of the reaction products but also on their types and purity. Other constituents of the soil-lime system affect the strength to varying degrees. While the increase in the amount of unreacted material at the expense of cementitious reaction products is not desirable, an amount of unreacted material is essential for other engineering requirements other than strength to be satisfied. Unlike other cemented composites, the strength of the soil-lime system is not related to the overall porosity of the system.

Published
1979

44. The properties and performance of high strength silica fume concrete

Author

Claisse, Peter Arnold and Cabrera, J. G.

Subjects
620.136
Abstract

Silicafume (SF) has been used as a partial replacement for cement in concrete and experiments have been carried out to measure the durability of the mixes. The SF mixes were made with 20% SF replacement of cement and waterlcement (wlc) ratios of 0.3 and 0.46. Three different curing conditions were used to simulate different site conditions and tests were carried out at 3,28 and 90 days after casting. The following properties were measuredfor the two SF mixes and the two control (OPC) mixes for each of the ages and curing conditions: corrosion rate of embedded steel by linear polarisation, electrical resistivity, carbonation depth, water vapour permeability, chloride permeability, oxygen permeability and porosity from helium and mercury intrusion. Samples were also investigated by thermogravimetric analysis. The resulting data matrix was analysed by using the method of analysis of variance to quantify the effect of the SF on the properties tested and their sensitivity to age and curing. It was also analysed by multiple regression to identify major effects of one property on another. It was concluded that SF will reduce the corrosion rate and that the major contributing factor is the substantial increase in resistivity that the SF causes. This increase in resistivity was found to be highly sensitive to cold curing in the short term but this effect was not permanent. The cause of the increase in resistivity is believed to be the depletion of calcium hydroxide which is caused by the pozzolanic activity of the SF. The analysis also indicated that the SF reduces the porosity in the .01-.15)1m size range and that this has a major influence on the durability.

Published
1988

45. Design of dense graded cold bituminous emulsion mixtures and evaluation of their engineering properties

Author

Nikolaides, Athanasios Fotiou and Cabrera, J. G.

Subjects
526.9
Abstract

A stable slow setting cationic emulsion has been developed, suitable to coat dense graded mixtures high in fine aggregate content, in particular gap graded rolled asphalt type and dense graded macadam mixtures. The slow setting emulsion, NH-10, is the outcome of an investigation into five different formulations using two surfactants, two adhesive agents and a water shading compound. The rheological studies of the NH-10 emulsion have shown that it possesses a thixotropic behaviour. The thixotropic behaviour has been justified by the "complex flow" coefficient, a technique proposed by Traxler for bitumens. The viscosity of the emulsion is greatly influenced by the amount of binder and level of temperature. The hardness of binder does not change appreciably the viscosity value of the emulsion. The highly stable mildly cationic emulsion has been used to prepare two types of dense bituminous mixtures containing limestone aggregate, river sand and limestone filler, blended in appropriate proportions. The study presents information regarding the properties of two dense graded bituminous mixtures i. e. a gap graded "Cold Rolled Asphalt" (C. R. A. ) and a continuously graded "Dense Emulsion Macadam" (D. E. Mc). A design procedure based on a modified Marshall method and the evaluation of permeability and creep stiffness is proposed as a laboratory method for the design of the bituminous mixtures developed. The evaluation of permeability and creep stiffness is carried out with equipment designed and developed specially for this investigation.

Published
1983

46. The nature and engineering properties of some red soils from North-East Brazil

Author

Malomo, Siyanbola Samuel and Cabrera, J. G.

Subjects
624
Abstract

Researchers over the years have demonstrated the need for the determination of the nature and fundamental properties of soils as an approach to the understanding of engineering behaviour. This has teen shown to be particularly true in the case of tropical soils. This thesis approaches the analyses of engineering behaviour from a standpoint of the study of the intrinsic properties. The mineralogy, chemistry, structure and strength behaviour of three concretionary red soils from Paraiba State in North-East Brazil, have been determined. The mineralogy- of the red soils were determined using X-ray analysis, differential thermal analysis and thermogravimetric techniques. The microstructure of the red soils has been examined with the optical and scanning electron microscopes. The strength behaviour of compacted specimens was examined in the oedometer, direct shear and triaxial machines. A phenomenon of breakdown of soil particles under stress is isolated. The influence of the phenomenon on the strength behaviour is demonstrated. The soil elements and properties responsible for the phenomenon are discussed.

Published
1977

47. 'Mathematical models for urban bus service optimization.'

Author

RABBANI, Soheil Rahnemay., MAHER, Michael John., LIPOWSKI, J. S., and CABRERA, J. G.

Abstract

Submitted by Deyse Queiroz (deysequeirozz@hotmail.com) on 2019-04-29T11:01:55Z No. of bitstreams: 1 SOHEIL RAHNEMAY RABBANI - DISSERTAÇÃO PPGECA 1975..pdf: 21720552 bytes, checksum: e3d86f328723e0fdcdc7f604d1742d0d (MD5) Made available in DSpace on 2019-04-29T11:01:55Z (GMT). No. of bitstreams: 1 SOHEIL RAHNEMAY RABBANI - DISSERTAÇÃO PPGECA 1975..pdf: 21720552 bytes, checksum: e3d86f328723e0fdcdc7f604d1742d0d (MD5) Previous issue date: 1975-11 Este trabalho descreve o desenvolvimento de alguns modelos matemáticos para a otimização de um serviço urbano do ônibus. Os custos indiretos a curto prazo representados por tempo total de viagem (tempos de caminhada, de espera e de deslocamento) dos passageiros que usam o sistema de transporte publico, é considerado e usa-se este como medida da eficiência do sistema. O problema é, então, a otimização da operação do sistema dentro da restrição do nível fixo de investimento de capital. As variáveis no problema incluem o número de ônibus em cada linha, as posições de paradas e as próprias linhas. Após o desenvolvimento de alguns modelos teóricos, o caso prático da operação do sistema de ônibus de Campina Grande, Paraíba, é considerado e algumas sugestões para melhorar o sistema são oferecidas. This paper describes the development of some mathematical models for the optimization of an urban bus service. The short-term indirect costs represented by total travel time (walking times, waiting times and displacement) of passengers using the public transportation system is considered and used as a measure of the efficiency of the system. The problem is, then, the optimization of the operation of the system within the constraint of the fixed level of capital investment. The variables in the problem include the number of buses in each line, the stop positions and the lines themselves. After the development of some theoretical models, the practical case of the operation of the bus system of Campina Grande, Paraíba, is considered and some suggestions to improve the system are offered.

Published
1975

48. Study of three soils stabilized with a cationic asphaltic emulsion

Author

FERREIRA, Ademir Montes., CABRERA, J. G., FERREIRA, Heber Carlos., CARVALHO, João Batista Q. de., and BORBA, Geraldo Ramos.

Subjects
Emulsão asfáltica - aplicação em solos, Emulsão asfáltica catiônica, Processo de cura acelerada - emulsão, Pavimentos flexíveis - construção, Sistemas solo-emulsão asfáltica, Engenharia Civil, Solos estabilizados com asfalto, Stabilized soils with asphalt, Asphalt emulsion - application in soils, Cationic asphalt emulsion, Estudo de solos
Abstract

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-10-02T15:37:29Z No. of bitstreams: 1 ADEMIR MONTES FERREIRA - DISSERTAÇÃO PPGECA 1980..pdf: 16537187 bytes, checksum: 2bde2139eea0b3c23fb1f2cb6809002e (MD5) Made available in DSpace on 2018-10-02T15:37:29Z (GMT). No. of bitstreams: 1 ADEMIR MONTES FERREIRA - DISSERTAÇÃO PPGECA 1980..pdf: 16537187 bytes, checksum: 2bde2139eea0b3c23fb1f2cb6809002e (MD5) Previous issue date: 1980-09 A falta de uma metodologia apropriada para o dimensionamento e ensaios de laboratório para condições locais representa a maior dificuldade para o emprego eficiente de sistemas solo-emulsão asfáltica na construção de pavimentos flexíveis. Esta investigação apresenta os resultados de um estudo de uma metodologia de cura acelerada. 0 processo de cura utilizado, secagem das amostras a 60°C durante 24h, mostrou-se plenamente satisfatório podendo ser utilizado no laboratório. As variáveis investigadas foram teor de umidade de compactação e quantidade de emulsão asfáltica catiônica Estas variáveis foram estabelecidas através da medida das seguintes propriedades: peso unitário, absorção, resistência à compressão simples e resistência ã tensão de tração indireta. trabalho mostra que o teor ótimo de umidade para máxima massa especifica aparente seca foi muito aproximada do teor ótimo de umidade para máxima resistência. E também mostrado que a porcentagem ótima de emulsão asfáltica pode ser determinada usando-se somente o critério da resistência máxima, pois os valores de absorção foram muito pequenos para os casos estudados, sendo inferiores aos máximos comumente utj_lizados por outros investigadores. Lack of appropriate testing procedures and design methods for local conditions are still the main drawbacks for the efficient utilization of soi1-asphaltic emulsion systems inflexible pavement construction. This investigationpresents the results of an study in which an accelerated testing procedure was deveioped and used. Three soils from the region north east were selected as representative of the local variations and used for the study. The variables investigated were compaction moisture content and quantity of cationic asphaltic emulsion.These variables were assessed by measuring the following selected engineering properties. Unit weight, absorption, unconfined compressive strenght and indirect tensile strength. The study shows that the optimum moisture content for maximum dry unit weight approximates very closely the optimum moisture content for maximum strength, it also shows that the optimum percentage of asphaltic emulsion may be determined using only the criterium of maximum strength since the values of absorption were in very case very small and far below of the maximumvalues commonly used by other investigators.

Published
1980

49. Study of the statistical variability of soil classification trials

Author

MARINHO, Reinaldo Lins., CABRERA, J. G., CASTRO, José Beltrão de., and NISHIDA, Yoshichika.

Abstract

Submitted by Ruth Quaresma de Freitas (ruth_quaresma@hotmail.com) on 2019-03-18T14:44:01Z No. of bitstreams: 1 REINALDO LINS MARINHO - DISSERTAÇÃO PPGECA 1976..pdf: 2780363 bytes, checksum: b728432a49e949b4c941b832c0a419ee (MD5) Made available in DSpace on 2019-03-18T14:44:01Z (GMT). No. of bitstreams: 1 REINALDO LINS MARINHO - DISSERTAÇÃO PPGECA 1976..pdf: 2780363 bytes, checksum: b728432a49e949b4c941b832c0a419ee (MD5) Previous issue date: 1976-05 O estudo apresentado nesta dissertação trata da reprodutibilidade de quatro ensaios de classificação de solos. É apresentada uma revisão crítica da literatura, nos métodos de ensaio e resultados de reprodutibilidade obtidos em outros países. 0 estudo de laboratório foi efetuado usando-se onze solos naturais, três solos beneficiados industrial mente e dois solos resultantes de misturas de solos natural e beneficiado. A reprodutibilidade do ensaio de Limite de Liquidez, ensaio de Limite de Plasticidade, Analise Granulométrica e ensaio de Densidade Real é apresentada em termos de repetibilidade e reprodutibilidade. 0 estudo de repetibilidade foi conduzido em um laboratório com o mesmo equipamento e o mesmo operador, enquanto o estudo de reprodutibilidade contou com a cooperação de dezesseis laboratórios (três de Universidades, oito de Organizações Rodoviárias Federais e Estaduais e cinco de Empresas Consultoras). Um estudo piloto foi também efetuado a fim de pesquisar as vantagens do uso do método do Cone de Penetração para a determinação do Limite de Liquidez de quatorze solos, dos dezesseis investigados. Analise estatística do estudo de repetibilidade mostra que os coeficientes de variação são comparáveis com outros reportados na literatura, enquanto os resultados de reprodutibilidade mostram muito claramente que os coeficientes de variação são extremamente sem aceitação. É mostrado que a reprodutibilidade dos quatro solos pesquisados e tão pobre que sua validade é contestada. E apresentada uma discussão dos métodos usados e são feitas sugestões para melhorar a reprodutibilidade dos ensaios. The study presented in this dissertation deals with the reproducibility of four soil classification trials. A critical review of the literature, test methods and reproducibility results obtained in other countries is presented. The laboratory study was carried out using eleven natural soils, three industrially benefited soils and two soils resulting from natural and beneficiated soil mixtures. The reproducibility of the Liquidity Limit assay, Plasticity Limit assay, Granulometric Analysis and Real Density assay is presented in terms of repeatability and reproducibility. The repeatability study was conducted in a laboratory with the same equipment and the same operator, while the reproducibility study was supported by sixteen laboratories (three from universities, eight from federal and state road organizations, and five from consulting firms). A pilot study was also carried out to investigate the advantages of using the Penetration Cone method to determine the Liquidity Limit of fourteen soils of the sixteen investigated. Statistical analysis of the repeatability study shows that the coefficients of variation are comparable with other reported in the literature, while the reproducibility results show very clearly that the coefficients of variation are extremely unacceptable. It is shown that the reproducibility of the four soils surveyed is so poor that its validity is disputed. A discussion of the methods used is presented and suggestions are made to improve the reproducibility of the assays.

Published
1976

50. Some physico-chemical and engineering proprieties of an organic clay from Recife

Author

CARVALHO, João Batista Queiroz de., CABRERA, J. G, GUSMÃO FILHO, Jaime de Azevedo., and FERREIRA, Heber Carlos.

Subjects
Amostras indeformadas - argilas, Recife - subsolo argila, Clay - physico-chemical properties, Engenharia Civil, Argila - propriedades físico-químicas, Organic clay, Argila orgânica, Recife - clay subsoil
Abstract

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-09-30T14:07:04Z No. of bitstreams: 1 JOÃO BATISTA QUEIROZ DE CARVALHO - DISSERTAÇÃO PPGECA 1975..pdf: 23722015 bytes, checksum: 8472b04995abaef083f89dbe9bba109e (MD5) Made available in DSpace on 2018-09-30T14:07:04Z (GMT). No. of bitstreams: 1 JOÃO BATISTA QUEIROZ DE CARVALHO - DISSERTAÇÃO PPGECA 1975..pdf: 23722015 bytes, checksum: 8472b04995abaef083f89dbe9bba109e (MD5) Previous issue date: 1975-03 0 propósito desta dissertação foi estudar "algumas propriedades físico-químicas e de engenharia de uma argila orgânica" que forma parte do subsolo da cidade do Recife. As "amostras indeformadas" foram retira das do subsolo pelo uso de tubos de parede fina sem costura conhecidos por tubos tipo "Shelby". Os resultados dos ensaios de laboratório foram obtidos com amostras retiradas ao longo da camada de argila orgânica com intervalos de 1,0 metro. Os ensaios, teor de umidade de campo, limites de Atterberg, análise granulométrica , área específica , pH, composição mineralógica, adensamento e triaxial não consolidado não drenado, permitiram não somente o estudo do solo em função da profundidade mas também sua caracterização. O estudo mostra que a homogeneidade e uniformidade da "argila orgânica" é provavelmente função da variação do teor de matéria orgânica. O solo é caracterizado como uma "argila orgânica" com baixo teor de matéria orgânica finalmente dividida, apresentando alta plasticidade, composta predominantemente do argilo-mineral caulinita, normalmente adensada e de baixa sensibilidade. Análise de regressão linear foi usada para explorar possíveis correlações entre os valores dos diferentes ensaios realizados. Isto mostra que, dentro das limitações do estudo, existem correlações entre os parâmetros medidos. Propõe-se que estas correlações sejam usadas preliminarmente para avaliar as propriedades de engenhar i d do solo estudado. The purpose of this dissertation was to study some physico-chemical and engineering properties of an "organic clay" which forms part of the soil profile underlying the city of Recife. Undisturbed specimens were recovered from the subsoil by the use of seamless, thin walled steel tubes known as "Shelby type tubes". Results during the laboratory testing programme were obtained from specimens recovered at 1 m intervals along the depth of the organic clay strata. Field moisture content, Atterberg limits, grain size distribution, specific gravity, specific surface, pH, minera1ogica1 analysis, consolidation and unconsolidated undrained triaxiol tests allowed not only the study of the soil as a function of depth but its characterization as well. The study shows that the homogeneity and uniformity of the "organic clay" is probably a function of the variation of organic matter content.- The soil is characterized as a: "soft organic clay with traces of highly divided inactive organic matter, exhibiting high plasticity, composed predominantly of kaolinite cl y mineral, normally consolidated and of low sensitivity". Linear regression analysis was used to explore possible correlations between the values of the different tests carried out. It is shown that, within the limitations of the study, statistical relations do exist between the parameters measured. It is proposed that these correlations may be used for preliminary evaluation of the engineering properties of the soil studied.

Published
1975

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