A capacidade de manter a estabilidade e integridade durante o tempo de exposição às forças destrutivas do intemperismo é um dos aspectos mais importantes da estabilização de solos em projetos de pavimentos. Esta dissertação apresenta resultados de um estudo laboratorial sobre o comportamento mecânico de um solo dispersivo estabilizado com cal. O solo estudado é um solo sedimentar de sedimentos quaternários pertencente à denominada região ocidental do Paraguai. O solo dispersivo se caracteriza por apresentar teores significativos de sódio e por apresentar erosão hídrica acelerada. O objetivo deste estudo foi avaliar a durabilidade de misturas de Solo-Cal submetidos a ciclos de molhagem e secagem. A resistência à compressão simples e resistência à vácuo saturação também foram examinadas para avaliar o desempenho de misturas de Solo-Cal. Medição da velocidade de pulso de ultra-som foi realizado como teste não destrutivo para monitorizar a rigidez das misturas. Os efeitos do tempo de cura, das características de compactação e do teor de cal, foram avaliados. Finalmente, desde um enfoque ambiental através da ferramenta de avaliação do ciclo de vida (ACV) foram avaliadas todas as misturas em função aos impactos ambientais potenciais gerados na construção de 1 m³ de subbase de Solo-Cal. Verificou-se que a durabilidade, a rigidez e a resistência de solos estabilizados com cal aumentam com o tempo de cura, com a energia de compactação e com o aumento do teor de cal. Além disso, a dispersibilidade intermediaria (ND4) que o solo apresentava em seu estado natural, muda para não dispersivo (ND1) com a adição de 2% de cal. Em conclusão ressalta-se que a mistura SC3-5 apresenta um melhor comportamento mecânico comparável com a mistura SC3-7, mas, com um menor impacto potencial gerado. / The ability to retain stability and integrity during the exposure time to the destructive forces of weathering is one of the most important aspects of soil stabilization in pavements design. This thesis presents the results of a laboratory study of the mechanical behavior of a dispersive soil stabilized with lime. The studied soil is a sedimentary soil of the quaternary sediments belonging to the so called western region of Paraguay. The dispersive soil is characterized by having significant levels of sodium and accelerated erosion. The objective of this study was to evaluate the durability of soil-lime mixtures subjected to wetting and drying cycles. Resistance to simple compression and resistance to vacuum saturation were also examined to assess the performance of soil-lime mixtures. Measurement of the ultrasonic pulse velocity was performed as non-destructive testing for monitoring the stiffness of the blends. The effects of curing time, the compression characteristics and lime content, were evaluated. Finally, all mixtures were evaluated from an environmental viewpoint by the life cycle assessment (LCA). All mixtures were evaluated according to the environmental impact in the construction of 1 m³ of Soil-Lime. It was found that durability, rigidity and resistance of soil stabilized with lime increases with cure time, with the energy of compaction and with increased lime content. Moreover, the dispersibility intermediate (ND4) showed that the soil in its natural state, changes to nondispersive (ND1) with the addition of 2% lime. In conclusion it is emphasized that the SC3-5 mixture has a better mechanical behavior comparable to SC3-7 mix, but with less potential impact generated.

O desenvolvimento sustentável impõe uma evolução do contexto sócio-econômico das obras que envolvem o uso do solo. Um efeito é a obrigação do uso de materiais localizados na obra ou nas imediações. Isto muitas vezes implica no uso de materiais de baixas propriedades de engenharia, surgem então alternativas de melhoria destes materiais, como a estabilização com cal. No entanto, sabe-se que o tratamento de solos pode ser ineficaz quando da presença de compostos químicos deletérios no solo. Esta dissertação apresenta resultados de um estudo laboratorial do comportamento mecânico de um solo laterítico estabilizado com cal cálcica e com cal dolomítica. Para avaliar a influência de agentes químicos, foram usados quatro tipos de fertilizantes químicos de uso comum na agricultura. O estudo incluiu a caracterização do solo, ensaios de compactação, difratometria de Raios-X e compressão simples do solo e das misturas solo-cal e solo-cal contaminado com fertilizante. Foram adotados teores de 1% de fertilizante e 4% de cal, os tempos de cura foram de 7, 14, 28, 56, 112 e 140 dias sob duas condições: cura em câmara sem controle de umidade e cura em câmara úmida a fim de avaliar a influência da perda de umidade sobre o ganho de resistência. Os resultados demonstraram que a adição de fertilizantes químicos diminuiu o ganho de resistência em até 13% em misturas com fertilizantes nitrogenados e cal dolomítica e até 36% em misturas com fertilizantes não-nitrogenados e cal cálcica. O ganho de resistência com cal cálcica foi o dobro do ganho com cal dolomítica, considerando os maiores valores observados. As misturas com cal dolomítica sujeitas à cura úmida tiveram maiores ganhos em todos os tempos de cura, apesar de pouco significativos; as misturas de cal cálcica tiveram maiores ganhos quando da cura em câmara sem controle de umidade, chegando a 60kN/m² a mais aos 56 dias. Em todos os ensaios de difratometria nas amostras de solo-cal e solo-cal contaminado com fertilizante observou-se a formação de calcita, em menor quantidade quando da contaminação por fertilizante. Verificou-se que a adição de fertilizantes ao solo pode alterar as características de estabilização do solo, o uso de cal cálcica traz maiores ganhos e que a perda de umidade e o controle da temperatura de cura pouco influenciam nos ganhos de resistência. / Sustainable development requires an evolution of the socio-economic development of the works involving land use. One effect is the obligation of using materials found on site or nearby. This often involves the use of materials of low engineering properties, improvement alternatives arise then these materials such as lime stabilization. However, it is known that the soil treatment may be ineffective in the presence of harmful chemicals in the soil. This thesis presents results of a laboratory study of mechanical behavior of a lateritic soil stabilized with calcic lime and with dolomitic lime. To assess the influence of chemical agents were used four types of commonly used chemical fertilizers in agriculture. The study included the characterization of soil, compaction tests, X-ray diffraction and unconfined compression tests (UCS) of soil and soil-lime and soil-lime contaminated fertilizer. The adopted levels was 1% of fertilizer and 4% lime, the cure times were 7, 14, 28, 56, 112 and 140 days under two conditions: curing in chamber without control of humidity and cure in a moist chamber to assess the influence of moisture loss humidity on the gain of resistance. The results showed that the addition of chemical fertilizers decreased the resistance in up to 13% in mixtures with nitrogen fertilizers and dolomitic lime and 36% in mixtures with nitrogenous fertilizers and calcic lime. The gain in strength with calcic lime was double the gain with dolomitic lime, whereas the highest values observed. Mixes with dolomitic lime be subject to wet cure had greater gains in all curing times, though insignificant, the mixtures of calcic lime had higher gains when the curing chamber without control of humidity, up to 60kN / m² more to 56 days. In all diffraction tests of soil samples with lime and lime-soil-fertilizer observed the formation of calcite, a lesser amount when the contamination by fertilizer. It was found that adding fertilizer to soil can alter the characteristics of soil stabilization, the use of calcic lime brings greater gains, and the loss of humidity of the moisture and temperature control of cure little influence on gains in strength.

Most soils in the Eastern Cape Province, South Africa are shallow and are low in organic matter. Therefore these soils are structurally fragile and highly susceptible to inherent degradative processes like hardsetting. The objective of this study was to determine the effect of cattle manure, scalping and soil wetness on aggregate stability, penetration resistance and early maize growth in hardsetting soils. Glasshouse and field studies were conducted to determine the effect of cattle manure on aggregate stability and penetration resistance of freshly exposed topsoils by scalping at 0, 10 and 20 cm depths. In the glasshouse cattle manure was applied at 0 and 20 Mg/ha and matric suction was kept at ~ 30 and ~ 400 kPa; contrasting high and low soil wetness. Three soils were put in pots and arranged in a randomized complete block 3 2 2 factorial design. The field study was done at the University of Fort Hare research farm and the treatments were arranged in a split-plot complete randomized design with three replications. Scalping treatment was the main plot whilst the quantity of the cattle manure applied was the sub plot. Cattle manure increased mean weight diameter (MWD) by between 48% and 71% under glasshouse and between 18% and 33% under field conditions, depending on the soil wetting rate. Cattle manure reduced MWD when the soil under field condition was subjected to mechanical shaking. Soil penetration resistance decreased linearly, with increasing soil wetness but it rapidly increased with increase in matric suction up to ~200 kPa and thereafter the rate of increase reduced. In the glasshouse, all treatments had no significant effects on shoot dry weight but low matric suction increased root dry weight by 133%. Interaction of cattle manure and low matric suction reduced shoot length by 6%, shoot fresh weight by 25%, root surface area by 36%, root length by 5% and root fresh weight by 29% compared to the control. In contrast, application of cattle manure and high matric suction increased shoot length by 37%, shoot fresh weight by 136%, root surface area by 159%, root length by 94% and root fresh weight by 119%. In the field, cattle manure application increased root length density and shoot dry matter by 26% and 30% respectively. Cattle manure improved the stability of aggregates of the hardsetting soil under rapid or slow water intake conditions experienced during rainfall or irrigation. However, under field conditions cattle manure acted as a deflocculant and decreased the stability of aggregates when mechanical stress was applied. The effectiveness of cattle manure in improving maize growth in hardsetting soils was determined by matric suction.

A questão central deste trabalho é demonstrar a viabilidade técnica e econômica da estabilização de solos com os cimentos pozolânicos de cinza de casca de arroz e de resíduo cerâmico. Para alcançar este objetivo o trabalho foi desenvolvido em duas etapas: a primeira referente ao desenvolvimento dos cimentos pozolânicos e a segunda referente à estabilização do solo propriamente dita. Em ambas as etapas adotou-se o critério da simplicidade e da possibilidade de utilização de equipamentos leves e de absorção de mão-de-obra não especializada. Os resultados técnicos e econômicos referentes ao cimento pozolânico de cinza de casca de arroz foram animadores; porém o mesmo não ocorreu com o cimento pozolânico de resíduo cerâmico que apresentou um desempenho em um patamar inferior. Quanto à estabilização de solos, os experimentos e a avaliação econômica efetuada mostram que a eficácia dos cimentos pozolânicos utilizados é limitada sendo difícil a obtenção de resultados comparáveis com o atualmente obtido com o cimento Portland. / The main scope of this work is to demonstrate the technical and economical viability of the soil stabilization with pozzolanic cements made from rice husk ash and waste bricks and tiles. In order to reach this objective the work has been developed in two stages: the first referes to the development of the pozzolanic cement and the second one referes to the soil stabilization. In both these stages the criteria that has been adopted was of the simplicity, of the use of light equipments and of non skilled labour. The technical and economical results referring to the rice husk ash pozzolanic cement were encouraging; but the same was not the case with the waste bricks and tiles pozzolanic cement that had an inferior performance. As regards the soil stabilization, the tests and the economical evaluation show that the efficiency of the pozzolanic cement is limited thus the results achieved are not as good as of the Portland cement.

Thesis. 1978. Sc.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / Vita. / Bibliography: leaves 342-349. / Sc.D.

Since the 1970's deep mixing columns have been widely used all over the world to improve the performance of soft soil in regard to bearing capacity or deformation behaviour. They are installed by mixing a binding agent, e.g. cement, in situ with the soil. The choice of installation method affects the properties of the column and the surrounding as the soil is disturbed by the installation process. However, the effects of the installation are often neglected during design even though they are plentiful. Besides the lateral displacement that could destabilize neighbouring constructions, the soil in the direct vicinity of the installed column is affected. Laboratory and field tests revealed the formation of three distinct zones outside the nominal diameter of the column which have different strength properties than the initial clay. They are formed due to cylindrical expansion, clay fracturing, and the migration of ions from the binding agent and their strength changes with time due to consolidation, cementation, heating, and thixotropy. Within this thesis, the installation effects that occur in the direct vicinity of the column have been studied in the context of a construction project in Sweden, where deep mixing columns are considered for the reduction of settlements of road and parks areas located on a thick clay layer. Based on analytical calculation methods and field measurements described in the literature, the occurrence and the magnitude of the installation effects have been assessed. The influence of considering these effects was then studied numerically using the finite element program PLAXIS. The simulation included one column within a column group and was performed in 2D assuming axisymmetry. The presence of the neighbouring columns was considered over the boundary conditions. The installation effects in the vicinity of the column comprised three zones which were implemented in the numerical model. For comparison, the simulations were also performed using the "wish-in-place" approach for the column that ignores the occurrence of any installation effects. The stabilized soil is loaded with two layers of new filling material which results in excess pore pressures and settlements that have been studied. The results for the model in which the installation effects were considered could be compared to the results for the model in which the column was wished-in-place. The comparison showed that the consideration of the installation effects leads to a faster consolidation and a significant reduction in settlements. This was observed for different installation patterns, i.e. triangular and square, and varying column spacings of 1.2 and 2.4 m. The positive installation effects were greatest for a smaller spacing and a triangular installation pattern. For a square installation pattern with a spacing of 2.4 m, the consolidation time and the final settlements were both reduced by more than 40%. Even though the assumptions and simplifications require verification, a clear positive influence can be seen for the project in Sweden. If these numerical results are confirmed by field observations, more efficient construction designs could be obtained which ultimately result in reduced costs and carbon dioxide emissions.

No description available.

No description available.

The purpose of the study was to define the characteristics of tree-length skidding on the Lower Coastal Plain of Georgia. The objectives were: 1) to document skidder performance based on speed and tire slip, 2) to determine the effects of skidding on soil physical properties, and 3) to develop recommendations to minimize the impact on soil properties while maintaining skidder performance. A Franklin 170 grapple skidder was operated in second gear under moist (19% moisture content) and wet (31% moisture content) soil conditions using 28L-26, 67x34-25, and 73x44-32 tires. One, three, nine, and 27 passes were tested. The skidder was also operated in third gear with the 73x44-32 tires under the wet soil condition. With moist soil conditions skidder speed and tire slip were not affected by tire size or the number of skidder passes. Tire size did not influence soil properties. It was recommended that skidding be dispersed to avoid making more than nine passes over any particular soil area because the research indicated that repetitive passes resulted in a cumulative decrease in non-capillary porosity and an increase in bulk density. During wet conditions, wheel slip increased, skidder speed decreased, and rut formation increased with smaller tires, an increase in the number of skidder passes, and second gear operation. Operating the skidder in third gear with the 73x44-32 tires was beneficial to skidder performance and a reduction in rutting. Recommendations were to disperse skidding to maintain productivity and minimize rutting. / Master of Science

Undrained triaxial tests were conducted to develop the constitutive relationships for two agricultural soils, which could be used for the finite element analysis of multipass effects of vehicles on soil compaction. Sandy-clay and sandy-silt samples were loaded and unloaded three times to levels of 138 kPa to simulate three passes of an agricultural tractor. An axial loading rate of 200 mm/min was used to include the dynamic effects of rapid loading from the vehicles. An Instron Universal Testing Machine was used to provide this loading rate. During the tests, a microcomputer based data acquisition system recorded axial force and strain. The system recorded 28 values per second. Tests were conducted at four confining pressures; 17.2, 24.1, 34.4 and 41.4 kPa. Plots for deviatoric stress and axial strain were found to be bilinear. Initial and latter portions of the curve were assumed to represent the elastic and plastic deformations of the sample, respectively. Assuming an associated flow rule, an elastic-plastic constitutive model was developed based on a Mohr-Coulomb failure surface. The constitutive model developed was evaluated by simulating a triaxial test at a confining pressure of 28 kPa. Initial conditions were computed by substituting the boundary stresses into the model to determine the elastic-plastic matrix. Incremental loads were applied up to the maximum stress level. For each increment of load, the elastic-plastic matrix was updated from the previous load application. The simulated data compared fairly well with experimental results, but tended to overpredict at higher stress levels. Based on a comparison with existing elastic-plastic models, the derived model appears to be well suited for substitution into the finite element method for studying soil compaction resulting from multipass effects of tractors. / M.S.