[Truncated abstract] Relationships between the persistence of organic matter added to soil, the dynamics of soil organic carbon (C) and phosphorus (P) were examined in four experiments on lateritic soils of Western Australia. The main objective was to quantify the release of P following organic matter application in soils which have high P adsorbing capacity. Another objective was to confirm that due to its recalcitrant materials, the effect of peat lasted longer in soil than other sources of organic matter in terms of increasing plant-available P fractions. Three experiments were conducted under glasshouse conditions for various lengths of time, with nine- to twelve-month incubations to investigate these hypotheses. As expected, organic matter with lower C:N ratios than peat (lucerne hay) decomposed more rapidly compared with peat, and the most active mineralisation took place within the first three months of incubation. Soil organic-C (extracted by 0.5 M K2SO4) had a significant positive correlation with P extracted with 0.5 M NaHCO pH 8.53. For a higher application rate (120 ton ha-1), peat was better than wheat straw and lucerne hay in increasing extractable bicarbonate-P concentrations in soil, especially at incubation times up to 12 months. Throughout the experiment, peat was associated with a steady increase in all parameters measured. In contrast to peat, nutrient release from lucerne hay and wheat straw was rapid and diminished over time. There was a tendency for organic-C (either in the form of total extractable organic-C or microbial biomass-C) to steadily increase in soil with added peat throughout the experiment. Unlike wheat straw and lucerne hay, extractable organic-C from peat remained in soil and there was less C loss in the form of respiration. Therefore, peat persisted and sequestered C to the soil system for a longer time than the other source of organic matter. Freshly added organic matter was expected to have a greater influence on P transformation from adsorbed forms in lateritic soils than existing soil organic matter. By removing the existing soil organic matter, the effect of freshly applied organic matter can be determine separately from that of the existing soil organic matter for a similar organic-C content. In order to do this, some soil samples were combusted up to 450° C to eliminate inherent soil organic matter. The release of P was greater when organic-C from fresh organic matter was applied to combusted soils than in uncombusted soils that contained the existing soil organic matter. The exception only applied for parameters related to soil micro-organisms such as biomass-C and phosphatase. For such parameters, new soil organic matter did not create conditions favourable for organisms to increase in activity despite the abundance of organic matter available. More non-extractable-P was formed in combusted soils compared to bicarbonate-P and it contributed to more than 50% of total-P. As for the first experiment, peat also showed a constant effect in increasing bicarbonate extractable-P in the soil

Orientador: Cassio Eduardo Lima de Paiva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-06T16:48:11Z (GMT). No. of bitstreams: 1 Berti_Carolina_M.pdf: 4127695 bytes, checksum: f8e52fd73231b7c47f0a12b5c7e759cc (MD5) Previous issue date: 2005 / Resumo: Esta pesquisa procurou estabelecer uma correlação entre os valores de capacidade de suporte resultantes dos ensaios CBR (Califórnia Bearing Ratio) versus DCP (Dynamic Cone Penetrometer), realizados com o solo proveniente de vias não-pavimentadas dentro do Campus da UNICAMP, situado em Campinas, São Paulo. O Cone de Penetração Dinâmica (DCP) é caracterizado como um equipamento simples, portátil e de baixo custo, cujo ensaio revela ser praticamente não-destrutivo. Com ele é possível determinar o perfil de resistência de camadas de solo compactadas ou em seu estado natural, controlar a execução de obras viárias e avaliar estruturas de pavimentos. Uma investigação do solo através de ensaios DCP e CBR conduziu ao desenvolvimento de modelos de regressão, correlacionando a capacidade de suporte obtida através de ensaios ¿in situ¿ com o auxílio do DCP, e ensaios de laboratório utilizando o ensaio de CBR e DCP. Através das informações contidas na literatura técnica, dos procedimentos experimentais efetuados e das análises de regressão realizadas, ficou evidenciado o relacionamento entre o DCP e o CBR, validando as correlações estabelecidas e propondo modelos próprios, aumentando a confiabilidade dos resultados dos ensaios DCP para avaliação da capacidade de suporte de solos / Abstract: This research establishes a correlation among the strength or supporting values of the tests: CBR (California Bearing Ratio) versus DCP (Dynamic Cone Penetrometer), accomplished with the soil originating from no-paved roads inside of the Campus of UNICAMP. The Cone of Dynamic Penetration (DCP) it is characterized as an equipment simple, portable and of low cost, whose tests reveals to be practically no-destructive. DCP test determines the profile of resistance of soil layers compacted or in your natural state, to control the execution of road buildings and to evaluate structures of pavements. An investigation of the soil through DCP and CBR tests led to the development of regression models, correlating the strength measures obtained through in-situ tests with the aid of DCP and laboratory tests using the CBR and DCP. Through the information contained in the technical literature, of the made experimental procedures and of the regression analyses accomplished, the relationship was evidenced between DCP and CBR, validating the established correlations and proposing own models, increasing the reliability of the results of the DCP tests for determining strength values of soils / Mestrado / Transportes / Mestre em Engenharia Civil

Les latérites sont les sols les plus utilisés dans les travaux de génie civil, plus particulièrement en construction routière dans la plupart des pays de la zone intertropicale. Ce sont des sols résiduels ou détritiques provenant de l’altération des roches préexistantes. Ces sols contiennent en quantité appréciable des oxydes de fer et d’aluminium, de la kaolinite et de la silice, mais de faibles quantités d’oxydes de titane, de manganèse, de magnésium, …, etc. La grande diversité des composés chimiques des latérites rend leur caractérisation malaisée. En outre, les documents normatifs et les guides techniques utilisés pour le dimensionnement des chaussées en Afrique subsaharienne pour la plupart inadaptés, ne prennent pas en compte la spécificité des conditions climatiques et environnementales des formations latéritiques dans les projets routiers. Une caractérisation interdisciplinaire de ces sols avec la prise en compte des facteurs intervenant dans le processus de latéritisation permettrait de déterminer des propriétés plus précises, plus pertinentes et beaucoup plus représentatives. Ce travail a pour vocation la caractérisation et la détermination de l’aptitude des sols latéritiques du sud-ouest du Niger. La zone concernée par l’étude comporte sept gisements latéritiques aux contextes géologiques forts différents les uns des autres. Notre étude, basée sur diverses approches a permis de déterminer les propriétés géotechniques et mécaniques des sols d’une part et les propriétés chimiques et minéralogiques d’autre part. À l’issue de l’étude, deux catégories de sols sont à distinguer : [1] les sols de bonne portance : d’indice CBR de l’ordre de 100 contiennent en moyenne une teneur en fines n’excédant pas 12% et un indice de plasticité inférieur à 15. Pour ces sols, la portance dépend beaucoup de la taille des particules. Ces derniers ont une résistance élevée au cisaillement et un angle de frottement interne effectif φ’ de l’ordre de 40° ainsi qu’une cohésion effective c’ supérieure à 10 kPa. Leur comportement est dilatant au cours du cisaillement. Ils présentent de faibles valeurs en indice de vide et en perméabilité. De même, leur amplitude de tassement est faible. La bonne portance de ces sols se justifie principalement par leur teneur appréciable en oxydes de fer. L’attaque de la matrice fine par ces derniers se fait de manière diffuse ou par concrétionnement sous forme de cercles d’oolithes et de pisolithes ovoïdes tangents. [2] les sols de faible portance : la fraction fine et l’indice de plasticité sont élevés, respectivement de l’ordre de 25 et 30. La portance est de l’ordre de 30, l’angle de frottement interne inférieur à 30° et la cohésion inférieure à 5 kPa. Ces sols résistent faiblement au cisaillement et leur comportement est contractant, c’est-à-dire celui d’un sable lâche. Ils sont plus compressibles, encore moins perméables avec un coefficient de gonflement élevé. La faible portance de ces sols est imputable à leur faible teneur en oxydes de fer, ainsi que le mode d’attaque qui se fait de manière isolée.L’amélioration des sols présentant une faible portance a été expérimentée en y rajoutant séparément une certaine teneur en liant hydraulique (ciment), en chaux (CaO) et en nodules latéritiques. Les analyses minéralogiques et chimiques ont montré que l’ajout des produits a conduit à une modification texturale et a favorisé la mise en place de composés chimiques néo-synthétisés ayant pour rôle principal de renforcer les liaisons entre les éléments minéraux contenus dans les échantillons de sol latéritique. Dans la plupart des cas, les échantillons améliorés ont présenté une bonne portance validant ainsi leur aptitude en construction routière. / Laterites are the most commonly used soils in civil engineering works, particularly in road construction in most countries of intertropical region. These are residual or detrital soils resulting from the alteration of pre-existing rocks. These soils contain a considerable quantity of iron and aluminum oxides, kaolinite and silica, but small quantities of titanium oxides, manganese, magnesium, etc. The large diversity of the chemical compounds of laterites makes their characterization difficult. Moreover, specification documents and technical guides used for road design in sub-saharan Africa, most of them unsuitable, do not take into account the specificity of climatic and environmental conditions of laterite formations in road projects. An interdisciplinary characterization of these soils, taking into account the factors involved in the lateritization process, should make it possible to be determined more precisely. It’s also the best way to get more relevant and much more representative properties. The aim of this work is to characterize and determine the lateritic soils suitability of southwestern Niger in road construction. The area covered by the study consists of seven lateritic deposits with strong geological different contexts from one to another. Our study, based on various approaches, made it possible to determine the geotechnical and mechanical properties of the soils on the one hand and the chemical and mineralogical properties on the other hand. At the end of the study, two categories of soils are to be distinguished: [1] soils with good bearing capacity : CBR of around 100 contain average fines content not exceeding 12% and a plasticity index less than 15. For these soils, the bearing capcity depends very much on the size of the particles. They have a high shear strength, an effective internal friction angle φ' of the order of 40° and an effective cohesion c' greater than 10 kPa. Their behavior is dilatant during shear. They have low values in void ratio and in index permeability. Similarly, their amplitude of settlement is low. The good bearing capacity of these soils is mainly justified by their appreciable iron oxides content. The attack of the microstructure by the latter is done in diffuse way or by concretionary circles of oolites. [2] the soils of low bearing capacity : the fine fraction and the plasticity index are high respectively of the order of 25 and 30. The bearing capacity is around 30, the internal friction angle is less than 30° and the cohesion less than 5 kPa. These soils are weak to the shear and their behavior is contracting (loose sand behavior). They are more compressible and less permeable with a high swelling coefficient. The low bearing capacity of these soils is attributable to their low iron oxide content and to the mode of attack which is carried out in isolated way.The improvement of soils with low bearing capacity has been tested separately by adding a certain amount of hydraulic binder (cement), lime (CaO) and lateritic nodules. Mineralogical and chemical analyzes showed that the addition of the products led to a textural modification and favored the production of neo-synthesized chemical compounds whose main role was to strengthen the links between the mineral elements contained in the lateritic samples. In most cases, the improved samples showed good bearing capacity and validated their road pavement suitability.