Navegando por CNPq "CNPQ::ENGENHARIAS::ENGENHARIA CIVIL::GEOTECNICA::MECANICAS DOS SOLOS"

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Acesso aberto (Open Access)
Análise comparativa das sensibilidades obtidas com o vane test e o mini vane em um depósito sedimentar na foz do rio Amazonas
(Universidade Federal do Pará, 2022-11-22) VIEIRA FILHO, Arudá Gomes; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
The reed test has been used in field research for the elaboration of geotechnical projects and in the management of non-clay sedimentary deposits, due to the fact that it provides data such as undrained shear strength (Su) and sensitivity (St). The same results are obtained in the test with the laboratory straw (mini vane), but for that, it is necessary to extract samples considered undisturbed, which, in this research, were recommended by the ABNT NBR 9820 standard. vane shear test with the laboratory vane test, also called Mini Vane. The location of this analysis is in a port region located at the mouth of the Amazon River, in a natural sedimentary deposit, which presented two slope disruptions with characteristics peculiar to soils with high sensitivity. Landslides on slopes are usually predictable from a geotechnical point of view, however in this researched region the soil presented rapid landslides on the slope, showing signs of a soil with high sensitivity. The research pointed out that the laboratory vane test (mini vane) presented a greater (St) when correlated with the (St) of the simple compression tests, giving greater clarity that there is a very soft clayey soil with a depth between 30 and 40 meters, typical of a ground lens that performed with high sensitivity. Comparisons between the reed tests showed consistency in the results, even in soil layers with different consistency indices than the initial layers, the validations of the reed tests were validated with the tests performed by simple compression. Finally, the soil of this deposit had its sensitivity identified in the field straw test. The same identification was confirmed on the Mini Vane. However, at depths greater than the field vane. In this way, the tests carried out by the Vane Shear Test (VST) in situ were primordial in the identification of the sensitivity, having its confirmation with the laboratory reed test (Mini Vane).
Acesso aberto (Open Access)
Análise comparativa entre uso e qualidade do solo na área do reservatório da UHE – Tucuruí com base nos atributos físicos e químicos
(Universidade Federal do Pará, 2018-12-21) RAMOS, Jaqueline Pinheiro; VILHENA, Karyme do Socorro de Souza; http://lattes.cnpq.br/3071495983880548
The construction of dams and their reservoirs generates a series of problems, among them, it is mentioned the erosions in the banks of the reservoirs. The soils forming the UHE-Tucuruí region are subject to different uses and occupations that over time have undergone changes with the seasonality of the lake and the increasing use of land, without considering the potentials and limitations of the soil. Some of these areas already show signs of degradation and erosion occurrence points are also identified. The present work seeks to determine the chemical and physical attributes for the evaluation of erodibility in soils located in the reservoir area of Tucuruí Hydroelectric Power Plant. With the selection of native forest, planting and pasture areas, the collected and deformed samples were collected to perform the chemical and physical tests at the Civil Engineering Laboratory of the Federal University of Pará at the Campus Universitário de Tucuruí. After obtaining the results of the physical and chemical properties of the soils can be prescribed the changes caused by the difference of their use and occupation, in the comparative between the areas, the established parameters showed the chemical degradation of the soil and the loss of nutrients that trigger the erosive processes. Multivariate analysis techniques were applied: Principal Component Analysis (PCA) and Hierarchical Grouping Analysis (HCA) to correlate the variables, the understanding of the data set was facilitated and the interrelation between the variables and samples became clearer, From these analyzes, it was possible to determine that the pasture area in the superficial layer is the one that most differs from the others, when considering all the attributes analyzed and the extracted samples, in addition, the multivariate analysis highlighted the information set, which variables are undergoing changes as a consequence of anthropic activity.
Acesso aberto (Open Access)
Avalanche como rede de percolação não homogênea
(Universidade Federal do Pará, 2019-09-13) SOUZA, Raimundo Nonato Carneiro de; TAVARES, Heliton Ribeiro; http://lattes.cnpq.br/1313373547379006; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
Avalanches can be considered as a percolation process. This hypothesis will be posted to evaluate if this approach is possible and what are its advantages. Some literature speculates that there is the possibility of considering avalanches as a percolation event. However, there is no clear distinction from the percolation model that these events describe, either a homogeneous or non-homogeneous process. This work deals with avalanche simulations as physical cases of percolation. To characterize the avalanches, two percolation models were simulated: homogeneous and heterogeneous. Simulations were developed to compare avalanches in both models. To perform these simulations, the probability of a site being open equal to 0:5 was used. The sizes and transients were measured for each avalanche in the different models. To close the work, experiments were carried out to create avalanches, in order to better calibrate the simulations using real avalanche data. For when comparing the simulated results with existing data in the literature, a typical behavior of a probability function was perceived. Given this behavior one can make predictions about the size of the avalanches. Analyzing the results obtained, it is possible that the behavior of avalanches created with non-homogeneous probability presented well defined characteristics, having larger values of size and transient. It was concluded that the non-homogeneous model has a high stability and is better in the evolution aspect of the avalanche, so with some adjustments the heterogeneous model can approach a real avalanche with greater accuracy.
Acesso aberto (Open Access)
Avaliação da sensibilidade de uma argila mole do Amapá por meio da correlação entre ensaios de CPTU e de laboratório
(Universidade Federal do Pará, 2022-11-03) GONÇALVES, Andrey da Costa; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
The identification and mapping of sensitive soft clayey soils are of great interest for planning, design and protection purposes, as these materials can exhibit fragility, loss of strength and softening by deformation, in addition to being more prone to landslides. The occurrence of sensitive clays in the port region of the municipality of Santana, state of Amapá, region of the mouth of the Amazon River, motivated the study about the geological and geotechnical characteristics of the local soil. In this context, this research aims to evaluate the sensitivity of clays from a fluviomarine sedimentary deposit. The geotechnical investigation was divided into three areas, called investigation islands. On each island, piezocone tests (CPTU) were performed and undisturbed samples of high quality soil were collected for laboratory tests. Soil behavioral type abacuses (SBT), which use CPTU data, indirectly identified layers (lenses) of sensitive soft clays. Through the relationship between the undrained soil shear strengths (𝑆𝑢 and 𝑆𝑢𝑟), obtained by the unconfined simple compression test, the sensitivity values were directly obtained. The Atterberg limit tests, total granulometric analysis and moisture content, served to characterize the region's soil. The results showed that the sedimentary deposit is constituted mainly by silt and clay, of low resistance and high plasticity and compressibility, with moisture content close to 50%. The methods of Robertson (1990) and (2016) and Schneider et al. (2008) identified sensitive thin material. The clay showed 𝐵𝑞 values lower than 1.0. The results for 𝑆𝑢 were between 33.67 and 103.53 kPa, while for 𝑆𝑢𝑟 between 4.44 and 16.29 kPa. According to Skempton and Nortey's (1952) classification, 83.33% of the samples were classified as medium to extrasensitive clays, with a sensitivity range of 3.3 to 12.7 and an average of 7.06. Thus, the results were consistent with similar ones in the literature, evidencing the applicability of the geological geotechnical investigation for identifying and mapping sensitive soils in the Amazon region.
Acesso aberto (Open Access)
Confiabilidade aplicada à análise da estabilidade de taludes: um estudo de caso de uma encosta fluvial no norte amazônico
(Universidade Federal do Pará, 2021-04-02) NASCIMENTO, Rafael Silva do; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
Among the geotechnical structures, the river slopes stand out for the uncertainties in their properties. In addition, the use of coupled reliability methods in the analysis of slopes has grown, in contrast to deterministic methods that do not consider uncertainties. In this context, the present work presents the study of the reliability of a fluvial slope in the Amazon region that suffered a rupture. For this, three reliability methodologies were used (Monte Carlo, FOSM and PEM), using the limit equilibrium method and finite elements. The properties of the hillside soft clays were treated as random variables and the reliability indicators for each methodology were obtained. In addition, sensitivity analyzes of these parameters were carried out. The results of the slice models were compared to the numerical results. Finally, it was concluded that the uncertainties in the properties of soft soils were not sufficient to cause the rupture of the slope, therefore, another factor(s) must have triggered the rupture.
Acesso aberto (Open Access)
Eletroquímica coloidal e sua relação com a sensibilidade de um solo argiloso na foz do rio Amazonas
(Universidade Federal do Pará, 2023-06-29) SOUSA, Flaviany Luise Nogueira de; TEIXEIRA, Marcelo Rassy; http://lattes.cnpq.br/8912916360456192
Clays have always played an important role in the history of civilizations, mainly because they are a mineral resource with varied technological applications. Among the several existing types, sensitive clays (quick clays), for example, are very complex soft soils that are considered real challenges for engineers due to the difficulty in obtaining their geotechnical parameters. In this sense, the aim of the present study was to analyze the sensitivity of a clay soil found in a region of the city of Santana, in the state of Amapá, Brazil. To this end, physical and chemical tests were carried out, including the SPT (Standard Penetration Test), X-Ray Diffraction (XRD), Zeta Potential (ζ), pH, Cation Exchange Capacity (CEC), as well as resistance assays (Vane Test and Fall Cone Test – FCT). The analyzed area is located in the Macapá Fluvio-marine Plain, which is composed of sediments that were deposited both by rivers and by the sea as a result of the region’s proximity to the mouth of the Amazon River. The geological profile obtained through geotechnical investigation indicated that the soil is constituted of mottled sandy-clay sediments, sandy-silty sediments with plant remains, and sandy- silty sediments with pebbles. As for the mineralogy of the samples, they were essentially composed of quartz and three clay minerals: kaolinite, mica/illite, and chlorite. Regarding sensitivity, all samples were classified as quick clays, with medium or high amounts of organic matter (O.M.); greater organic matter content was associated with increased sensitivity. In addition, it was understood that the intensity of clay sensitivity was higher with the increase in monovalent cations and the decrease in divalent cations such as Ca2+ and Mg2+, which must have been removed by the O.M. The soil pH reading ranged from high to very high acidity, an expected classification due to the increase in H+ concentration due to the O.M. All samples showed similar ζ values, with the lowest being 31.3 mV and 33.2 mV, which are still considered high, indicating that the soil colloids repel each other, forming a dispersed structure. Our results were consistent with similar reports in the literature; however, regionalized studies are necessary for a better understanding of the local peculiarities capable of influencing the profile of this soil.
Acesso aberto (Open Access)
Estudo da erodibilidade de solos do reservatório da UHE Tucuruí
(Universidade Federal do Pará, 2019-10-30) SILVA, Lucas Manoel da; GOUVEIA, Fernanda Pereira; http://lattes.cnpq.br/1772072130947378; ALENCAR JÚNIOR, Júlio Augusto de; http://lattes.cnpq.br/3663658632717465
The Tucuruí Hydroelectric Power Plant, besides being the 5th largest hydroelectric plant in the world in generating capacity, transfers electric power to several Brazilian states and, having a reservoir of 2,917 km², is strongly subject to erosion. Several studies report the occurrence of erosive features near the its reservoir, besides being constantly subjected to laminar erosive actions in its drainage areas. In this work we carried out bibliographical surveys, field checks and direct and indirect analyzes of the erodibility of samples of the main soils of the Tucuruí HPP reservoir. Indirect analyzes employed semiempirical formulations based on physical and geotechnical characteristics of the, and the direct ones tested undisturbed samples under runoff, exposure to gradual and total water immersion processes, and under intense sample remoulding levels for evaluations in the Tropical Compacted Miniature - M.C.T. It was possible to notice a significant increase in the reservoir territorial occupation, favoring the exposure to erosive processes, and that the samples classified as Pedisol as Ultisol and Yellow Latosol presented average erodibility rates, as 0.0392 and 0.0323 g / cm² / min / Pa and low levels of disaggregation, while Red Latosol presented low erodibility as 0.002 g / cm² / min / Pa, medium to high levels of disaggregation and expansions, in the MCT methodology. These conclusions indicate that the agricutural activity in the area must grow crops that maintain the surface coverage of the first soil areas, and the prevention of uses that may disrupt and damage the last soil.