Orientador: José Euclides Stipp Paterniani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-23T10:41:16Z (GMT). No. of bitstreams: 1 Cavalhieri_CaioPompeu_M.pdf: 3818458 bytes, checksum: 75bf1f2391a40c8e0f8f527257f97c8a (MD5) Previous issue date: 2013 / Resumo: Idealizadas para prevenir e controlar problemas associados à intensificação de processos erosivos, cercas-silte ou silt-fences são cada vez mais comuns em canteiros de obra. Feitas com mantas de geotêxtil estruturadas sob a forma de barreiras verticais, essas cercas promovem a detenção das águas pluviais que escoam sobre a superfície do terreno e, dessa maneira, favorecem a remoção de sedimentos em suspensão no runoff por meio da combinação dos efeitos de sedimentação e filtração. Assim, considerando-se a relevância que as mantas de geotêxtil têm sobre a qualidade de todo o processo, este estudo avaliou o desempenho de geotêxteis não-tecidos em relação à remoção de sólidos suspensos. Para tanto, experimentos foram realizados em laboratório e, com o intuito de aproximar os ensaios ainda mais da realidade, os experimentos foram feitos com: (a) mantas em duas situações distintas (sem nenhum tipo de uso e retirada de um canteiro de obra após dois anos de uso contínuo como cerca-silte); (b) solo coletado no mesmo canteiro de onde veio o geotêxtil usado (para compor o runoff dos ensaios em média com 800 UNT); (c) escoamento do runoff na direção horizontal; e, por fim, (d) parâmetros de ensaio baseados em critérios de projeto e também na equação de chuva da área mais próxima da obra de onde vieram as amostras de solo e geotêxtil usado. De maneira geral, os dois tipos de geotêxtil (novo e usado) favoreceram a redução de sólidos em suspensão durante os ensaios, embora esse efeito tenha sido estatisticamente mais significativo na manta retirada da obra. Além disso, valores de turbidez menores do que 40 UNT (parte inferior aos 5,0 UNT preconizados para consumo humano) estiveram associados a taxas de escoamento relativamente baixas (menores do que 20 mm/min). Entretanto, há que se considerar que, em determinados contextos, baixas taxas de escoamento também têm potencial para gerar repercussões indesejáveis. Daí a importância de se contar com a boa fundamentação de projetos, atividades de instalação e serviços de manutenção, de maneira que os resultados esperados sejam compatíveis com os obtidos em situações reais / Abstract: Developed to prevent and control problems associated with the intensification of erosion, silt or silt-fences-fences are increasingly common in construction sites. Made with geotextiles structured in the form of vertical barriers, these fences detain rainwater runoff and, thus, promote the removal of suspended sediments through sedimentation and filtered. Considering the relevance geotextiles have on the quality of the entire process, this study evaluated the performance of non-woven geotextiles regarding the removal of suspended solids. Therefore, experiments were performed in the laboratory and were made with: (a) blankets in two distinct situations (without any use and removed from a construction site after two years of continuous use as fence-silt); (b) soil collected in the same plot where the geotextile was used as silt-fence (to compose the runoff tests averaged 800 UNT); (c) runoff flow in the horizontal direction; and finally, (d) test parameters based on design criteria and also the rain equation of the closest area to the work from which the samples of soil and geotextile came from. In general, the two types of geotextile (used and new) promoted reduction of suspended solids during the tests, although this effect was statistically significant over the blanket removal of the work. Furthermore, turbidity values lower than 40 NTU (5.0 NTU at the bottom recommended for human consumption) were associated with relatively low flow rates (less than 20 mm / min). However, it is necessary to consider that, in certain contexts, low flow rates also have the potential to generate undesirable impacts. Hence the importance of relying on consistent projects, activities of installation and maintenance services, so that the expected results can be consistent with those obtained in real situations / Mestrado / Saneamento e Ambiente / Mestre em Engenharia Civil

M.Ing. (Civil Engineering) / The purpose of this study was to determine the effectiveness of a sisal fibre natural geotextile in controlling the rate and extent of soil erosion. The effectiveness of this locally produced material was compared to other natural fibre geotextiles and other methods commonly used for the control of soil erosion. The different materials and methods were tested under the same conditions to compare the relative effectiveness of these products. The various erosion control products were subjected to laboratory tests. A rainfall simulator and an adjustable slope simulator were used to simulate the process of soil erosion. During these tests the effectiveness of the different products in controlling soil erosion was measured and conclusions were made about the effectiveness of the products. Mechanical sieve analysis tests were used to determine the erodibility of the different soil particles. Field trials that made use of the sisal fibre geotextile are also discussed.

[pt] A ocupação e uso dos solos têm claras implicações nos processos erosivos, porém devemos destacar também um dos atores principais para os processos erosivos, que é a evolução geomorfológica. A bacia do córrego das Palmeiras está inserida em um local com baixas amplitudes de relevo, mas que apresenta um alto potencial de vulnerabilidade a eventos de erosão e movimentos de massa. Destacamos obviamente o grande número de voçorocamentos que atingem determinadas áreas do médio vale do rio Paraíba do Sul, principalmente próximos ao seu eixo principal em um grande alinhamento de direção NE-SW a qual a bacia do córrego das Palmeiras está inserida. O presente estudo tem como objetivo principal descrever a origem e a distribuição dos processos erosivos na bacia do córrego das Palmeiras, na cidade de Barra do Piraí, Rio de Janeiro. Para que o principal objetivo desse trabalho seja alcançado, se torna necessário o cumprimento dos objetivos específicos, os quais são: Descrever a relação da orientação das voçorocas com as estruturas do substrato geológico; Descrever a relação entre processos erosivos e os níveis de base locais e; Descrever a relação entre processos erosivos e uso do solo. Para a realização deste trabalho foram utilizadas técnicas de análise e embasamentos teóricos da ciência geográfica e mais especificamente da área da geomorfologia. Podemos destacar como os principais resultados alcançados as análises referentes à relação entre os condicionantes geológicos/geomorfológicos e a ocorrência e comportamento de processos erosivos, permitindo afirmar que existe uma relação estreita entre a compartimentação geológica, orientação das estruturas, processos de rebaixamento de níveis de base, histórico de uso e ocupação do solo e a presença de processos erosivos. / [en] Land use has clear implications in the erosive processes and their relation with the geomorphological evolution can be seen notoriously. The Palmeiras stream basin is inserted in a place with low amplitudes of relief, but that presents a high potential of vulnerability to events of erosion and mass movements. We highlight obviously the large number of gully erosions that reach certain areas of the middle valley of the Paraíba do Sul river, mainly near its main axis in a great alignment of direction NE-SW to which the basin of the stream of Palmeiras is inserted. This study has as main objective the description of the origin and spatial distribution of the erosive processes in the Córrego dos Palmares basin. In order for the main objective of this work to be achieved, it is necessary to fulfill the specific objectives, which are: Analyze the spatial distribution of erosive processes; analyze the relation of the orientation of the gullies with the lithological structures of the geological substrate; Analyze the relationship between erosive processes and local base levels and; analyze the relationship between erosive processes and land use. For the accomplishment of this work, techniques of analysis and theoretical bases of the geographic science and more specifically of the area of geomorphology were used. We can highlight as the main results of the description the relationship between the geological / geomorphological conditions and the occurrence and behavior of erosive processes, allowing to affirm that there is a close relationship between the geological compartmentation, orientation of the structures. History of land use and occupation and the presence of erosive processes.

M.Sc. (Geography) / This study concentrates. not only on the physical and chemical factors influencing erosion levels in the Pilanesberg area, but also on the impact of anthropogenic factors such as artificial drainage and other cultural irregularities that have modified the local catchment in the Pilanesberg area. For this reason, a comparative study of soil erosion has been made across the perimeter of the Pilanesberg Nature Reserve. The study'aimed to analyze the impact of climatic factors, chemical and physical properties of the soils on the local erosion system. Possible triggering mechanisms of the erosion have been discussed and conservation concerns in the Pilanesberg area have been raised. Of major importance in this study has been the'estimation of soil loss rates across the perimeter of the PNR.. This was premised on the 'rationale that population pressure has an impact on the local erosion system, Through the' analysis of sediment trapped at the monitoring sites it has been possible to indicate the tremendous impact of population pressure on the slopes of the Pilanesberg hills, just outside of the PNR. The rate at which soil is lost on the surrounding rural landscape in the Pilanesberg area has been found to be on average. nearly four times higher than inside of the PNR.

The research aim was to assess the vegetation and soils of the Rora /' Habab plateau, Eritrea and to develop methods of propagating the native tree species, juniper and olive. The research consisted of vegetation and soil surveys, interviews with local people, archival research, and experiments on propagation of olive and juniper. Junipers are now confined to the north of the plateau. Olives are more abundant in the north but have very few individuals in the centre, where there are many dead trees, or south. Soil erosion was ubiquitous and often severe. Soil morphology and nutrient status were related to vegetation, topography, land use, and erosion status, and varied greatly over short distances. Soil texture was coarser and most chemical factors (except total Ca and exchangeable Na) were lower in the south. Organic C, total N, exchangeable Ca, percent day, CEC and the sum of bases were higher in soils from grazed land than in cultivated fields. Germination of olive seeds was 92% when the endocarp was removed; stratification had little effect. Rooting of olive stem cuttings attained 76% under mist when parent plants were fertilised and cuttings were treated with rooting hormone. Germination for juniper was 56% after stratification at 5°C for 30 to 60 days. Juniper stem cuttings rooted in only one of three experiments, where rooting was 78% in a well ventilated, cool, low-mist environment. Olive seedlings which were fertilised and watered every 7, 14, or 21 days for two months, were taller, had lower root:shoot ratios and soil moisture than unfertilised plants. Fertilised seedlings watered every 28 days died. Root volume was less for plants watered every 21 days but watering interval had little effect on other variables in unfertilised seedlings. Ecological restoration is urgently required to rehabilitate the Rora plateau, which has Africa's most northerly remnant juniper / olive woodlands.

The study examines the effect of ridged pineapple cultivation on factors influencing the soil erodibility of Glenrosa and Oakleaf soil forms in the Bathurst district of South Africa. A number of physical and chemical variables influencing soil erodibility are investigated, namely soil moisture, bulk density, porosity, infiltration rate, aggregate stability, shear strength, soil texture, soil structure, penetrability, organic carbon, pH and cation exchange capacity. These soil characteristics are examined in undisturbed soils under natural vegetation and compared to those on adjacent traffic areas, pineapple ridges and pineapple furrows. The results of the analyses between the four sample sites indicate that ridged cultivation of pineapples has a negative effect on factors influencing soil erodibility on the areas studied. The results of the analysis within each of the sample sites do not illustrate any clear relationships and thus depict the complexity and multiplicity of the soil erodibility phenomenon. A further study, augmenting the soil erodibility data with actual soil loss data, is recommended

On most tropical volcanic islands the risk for soil erosion is enhanced due to a complex topography, high intensity rainfall and the exploitation of land for agriculture. Mauritius is a typical maritime tropical volcanic island with a distinct elevated interior. Rainfall is dominated by tropical weather systems and trade winds and the island is under intensive cultivation. Rainfall depth, duration, intensity, kinetic energy and erosivity were analysed for 385 erosive rainfall events at five locations over a five year period (2004 to 2008) on the island of Mauritius. Two stations located on the west coast and three stations sited on the Central Plateau above 550 m a.s.l. are used to provide detailed rainfall data at six minute intervals. Erosive storm events, defined here as a total rainfall exceeding 12.5 mm and a maximum 6-minute intensity exceeding 25 mm/hour, are found to differ markedly between the coastal lowlands and the elevated interior with regards to the frequency, the total rainfall generated, the duration, total kinetic energy and total erosivity of individual events. However, mean kinetic energy, mean and maximum rainfall erosivity (EI30) and maximum intensities (I30) from individual erosive events do not show this distinct differentiation. Erosivity measured during summer exceeds that recorded in winter, but the data indicate that large percentages of winter rainfall on Mauritius are defined as erosive and non-tropical cyclone rainfall can pose a substantial erosion risk. In this maritime tropical environment with its elevated interior, soil erosion risk occurs from storm scale to synoptic scale rainfall events and extreme events generate the bulk of the erosivity. Findings show that using rainfall records at an event scale within soil erosion risk assessments on tropical islands with a complex topography will increase the effectiveness of erosivity estimates

Les berges des grands fleuves soumis à des crues saisonnières et aux effets de la marée sont l’objet de glissements et d’éboulements causant des dégâts matériels et parfois des victimes humaines. Le présent travail consiste à étudier la stabilité des berges de rivière soumises à la marée en considérant l’influence des écoulements externe et interne de l’eau sur le massif du sol. On considère en particulier l’effet de la fluctuation du niveau d’eau à l’extérieur et à l’intérieur du massif sur la pression interstitielle dans le sol. Le modèle d’écoulement de Dupuit est adopté pour trouver la variation de la surface libre dans le massif. Une méthode des tranches est programmée pour calculer les coefficients de sécurité au glissement des berges soumises à la marée. Des études paramétriques sur la géométrique de la berge, sur les caractéristiques hydromécaniques du sol et sur celles de la marée sont ensuite présentées. L’érosion superficielle de la berge est simulée par différentes méthodes et couplée avec le calcul de stabilité. Enfin, des études des cas sur la baie du Mont-Saint-Michel et sur les rives du Mékong inférieur sont présentées.La comparaison entre les simulations et les mesures de surface libre pendant les marées nous permet de conclure quant à la pertinence du modèle d’écoulement de Dupuit dans le cas de milieux relativement homogènes et isotropes. Mais celui-ci s’avère moins précis pour des milieux plus complexes, tels que les milieux multicouches. La marée a un effet important sur les pressions interstitielles dans le sol, lesquelles subissent des phénomènes d’amortissement et de retard.Les facteurs de sécurité au glissement varient en fonction de la marée et ils sont minimaux pendant le reflux avant la basse mer à cause du retard de la surface libre dans le sol et de la décélération de la vitesse descendante de la marée avant la basse mer. Des abaques sont proposés donnant les domaines de sécurité en fonction de différents paramètres du sol, de la géométrie de la berge et de la marée. Ces abaques permettent également le calcul du coefficient de sécurité par interpolation linéaire.Quand la berge est submergée pendant un temps suffisamment long, la zone de rupture du massif se localise dans la partie supérieure de la berge et se produit à la pleine mer. Ce mode de rupture est observé aussi sur les sites étudiés (Mont-Saint-Michel). Au reflux, on met évidence un deuxième mode de rupture correspondant à des surfaces de glissement plus profondes liées à des pressions interstitielles résiduelles élevées.Dans la période de décrue (site de Kaoh Chorram), le coefficient de sécurité diminue avec la baisse du niveau de l’eau sous le sommet de la berge. A même niveau d’eau dans la rivière, le coefficient de sécurité à la décrue est inférieur à celui résultant d’un état d’équilibre. Des différences importantes s’observent aussi sur les surfaces de glissement entre les deux régimes. / The riverbanks, subjected to seasonal flooding and tidal variation, are submitted to landslides causing property damage and sometimes human victims. The presented work is conducted to analyze the riverbank stability subjected to the tide variation by considering the influence of external and internal water flows on the bank soil. More particularly, we consider the effect of ground water variation on the soil pore pressure. The Dupuit’s flow model is adopted to find the variation of the ground water table. A method of slices is developed to calculate the safety factor of riverbank slides as a function of tide. Parametric studies of the effect of bank geometry, hydromechanical soil properties and the characteristics of tide variation are then presented. Then the bank surface erosion is simulated by different methods and coupled with the calculation of landslide. Finally, case studies at Mont-Saint-Michel bay and on the lower Mekong riverbank are conducted.The comparison between simulations and field measurements of ground water table during the tide variation let us conclude that the Dupuit’s flow model can be adopted for homogeneous and isotropic soils. However, the mode is less accurate for more complex media, such as multilayered soils. The tide has a significant effect on the pore pressure in the soil, which creates damping and delayed phase phenomena with respect to the tide.Slide safety factors vary as a function of tide and they are minimal during the falling of water level before low tide due to the delay of the ground water table and the slowing down of the speed of the tide. Charts of safety factor have been proposed providing the security domains based on various soil parameters, bank geometry and tide variation. These charts also allow calculation of the safety factor by linear interpolation.When the bank is submerged for a time period long enough, the failure surface is located in the upper part of the bank and occurs at high tide. This failure mode is also observed in the field study (Mont-Saint-Michel). During the falling of tide from the bank surface, the second mode of failure is observed corresponding to deeper slip surfaces associated with high residual pore pressures.In the period of decline after flooding of the bank (Kaoh Chorram site), the bank safety factor decreases with the falling of water level below the top of the bank. At the same water level in the river, the safety factor during decreasing water level is smaller than that during the steady state. Significant different failure surfaces are observed between the two regimes.

An understanding of runoff generation is a requirement for efficient erosion control and land management practices. This research is designed to investigate the processes by which runoff occurs on a Whatcom soil at an upland site in the Lower Fraser Valley. The objectives of this study are to summarize water erosion measurements, to determine soil hydraulic properties, to predict infiltration for typical rainstorms and to determine the mechanism of runoff generation. Rill, interrill and rainsplash measurements, and previous erosion measurements made at the study site are used to qualitatively assess the magnitude of water erosion. Soil loss is dominated by rill erosion and erosion rates are greatest from November to January. Runoff coefficients are relatively low (<26%), but erosion rates are anticipated to be in excess of 35-45 t ha⁻¹yr⁻¹. Soil hydraulic properties are measured using a low tension absorption technique described by Clothier and White (1981). The sorptivity tube device provides a simple method for obtaining S, λ* and K₋₂ Measured values of i and x* depend on t¹′² as expected from the constant-concentration absorption theory. Soil hydraulic variables and constant-concentration absorption theory are used to determine the soil-water diffusivity characteristics. Measured D(θ) functions for the field varied widely in a and b, especially for the lower horizons. The Van Genuchten (1980) θ(h) expression provides a good fit to the water retention data. D(θ) functions predicted from the soil-water retention curves and the conductivity at satiation are at least 1-2 orders of magnitude greater than the measured functions. Hysteresis effects may account for a 1 order of magnitude increase in D(θ), but the predictions are poor without matching at D(θ₅). The measured hydraulic properties are used to predict infiltration, runoff and drainage. Constant-flux infiltration theory is used to model soil moisture profiles for various rainfall events. High field moisture contents necessitate the inclusion of gravity effects during infiltration. Rainfall, runoff and soil loss measurements at the Mahal farm indicate that rainfall intensities <10 mm h⁻¹ cause considerable runoff and erosion. For rainfall intensities known to cause runoff and erosion, runoff is not predicted for most Ap horizon cores. Infiltration may be restricted at some sites by the lower horizon but runoff is not predicted at many sites. To evaluated soil moisture conditions between rainfall events, drainage is estimated from a unit gradient model. A rapid decrease in θ between rainfall events predicted by the unit gradient model, but θ measured at the Mahal farm suggests limited drainage between rainfall events. Rainfall, runoff and soil loss measurements suggest that factors other than those measured are contributing to the runoff observed in the field. Compaction, surface sealing and subsurface seepage may be factors influencing runoff and moisture conditions in the field. The high moisture contents observed in the field suggest the water table is perching on a layer of lower conductivity which in consistent with Dunne runoff. However, the measured infiltrabilities suggest Hortonian runoff and the resultes of the thesis are not conclusive with respect to the mechanism of runoff generation. / Land and Food Systems, Faculty of / Graduate

Rural agriculture in Mlondozi, as for South Africa, is has a low productivity, which is the result of poor knowledge, information, beliefs and land tenure which limits the acquiring of loans for inputs. A LandCare Project was conducted for four years. Training was in the form of farmer managed research demonstrations which included the taught Conservation agriculture farming system which they compared to the Traditional farming system. Eighteen farmers initially joined the program and their soils were monitored for four years. At the end of the project undisturbed soil samples were taken from their fields where maize was cultivated following no-till (NT) farming system, and the conventional tillage system (CT). The soils from the two farming systems were compared using a laboratory rainfall simulator for run-off, erosion and infiltration. Each storm event in the rainfall simulator lasted for a period of 110 minutes (50 rotations). There were two statistical analyses done on the results. The first was a t-test was applied to the data to test for differences between the two systems, with a sample size of 72, at 18 sights with 4 replicates, except for carbon which was 36 analyses for the 18 sights. There was a significantly higher soil loss for NT soils for storm 1, compared to the CT soil, and a non significant difference for run-off for storms 1 and 2. Infiltration was significantly lower for the NT soil for the first storm, and not significantly higher for the NT soil for the second storm. The CT soils had a significantly higher infiltration rate for the first 16 rotations. After 68 minutes (rotation 34) the NT soils infiltration rate was higher. For simulated storm 2 the CT soils had a slightly higher infiltration rate up to 32 minutes (16 rotations) where after NT soils had a higher infiltration rate. Between 48 and 80 minutes (rotations 24 and 40) the NT soils had a significantly higher infiltration rate. From the results it can be concluded that the NT soils maintained the aggregate stability far longer than the CT soils. The initial and final infiltration rates were compared for the NT and CT soils for the simulated storms 1 and 2. The CT soils’ initial and final infiltration rate was similar, while the NT soils had a higher initial and final infiltration rate for the second storm, due to the soils settling with the first storm. The results question current literature that states that sealing of soils is a permanent feature. The carbon content of the NT soils was not significantly higher than the CT soils, which corresponded with the results. / Dissertation MInst (Agrar)--University of Pretoria, 2014 / gm2015 / Plant Production and Soil Science / MInst (Agrar) / Unrestricted