Frederico Garcia Sobreira

The use of GPR for characterizing underground weathered profiles in the sub-humid tropics

Ground penetrating radar (GPR) has been used as a tool to access information about ground subsurface features. Such information is very important for different types of studies, varying from those related to archeological research to those studying geological elements of bedrock. More recently, however, GPR has been increasingly applied to environmental studies, especially for soil research. This paper presents the results of an application of GPR for the study of weathered profiles. GPR was used to discover the degree of trustworthiness of the information on the ground subsurface through the interpretation of the results of the radar sections as well as the data collected from boreholes, which reached until 21 m. The results show a relatively high degree of details obtained by GPR, indicating the possibility of speeding up ground subsurface surveys related to geomorphological, geological, and pedological studies.

Comportamento hidrológico superficial e erodibilidade dos solos da região de Santo Antônio do Leite, Distrito de Ouro Preto - MG

O presente trabalho analisou o comportamento hidrologico superficial e a erodibilidade dos solos na regiao de Santo Antonio do Leite (Ouro Preto-MG), que se destaca pela intensidade e pelas proporcoes gigantescas de processos erosivos em forma de ravinas e vocorocas. Esse estudo analisou a resistencia da camada superficial dos solos, em relacao as chuvas, que, nesse caso, constitui-se no principal agente erosivo. Para tanto, monitorou-se uma vertente, atraves de parcelas de monitoramento de erosao laminar, ensaios de infiltracao, ensaios de Inderbitzen, ensaios de estabilidade de agregados do solo e analise granulometrica. Pode-se concluir que a camada superficial dos solos da regiao e resistente a erosao laminar e que essa camada serve como uma superficie protetora dos horizontes sub-superficiais, que sao friaveis quando impactados pelas chuvas. No entanto, a regiao e palco de grandes vocorocas e, dessa forma, pode-se entender que algum disturbio de ordem natural ou antropica deve ter ocorrido, para romper essa camada superficial e auxiliar no surgimento e/ou desenvolvimento das feicoes erosivas observadas. Esse trabalho teve o apoio da Fundacao de Amparo a Pesquisa de Minas Gerais (FAPEMIG).

Análise temporal da flora nativa no entorno de unidades de conservação: APA Cachoeira das Andorinhas e FLOE Uaimii, Ouro Preto, MG

The increasing fragmentation of the landscapes has contributed for the loss of the biological diversity in many Brazilian regions. In most cases, this is due to the disordered manner in which man has been using and occupying lands. The creation of protected areas or conservation units (UC) has been one of the main mechanisms used for the protection of biodiversity (in situ), in addition to commit wider objectives as for example the protection of the hydro resources, of threatened species, genetic resources, degree of endemism, habitats, among others. However, it is necessary the existence of periodic evaluation tools of its conservation status aiming at suppling subsidies to management plans by identifying the potential threats to the ecological functionality of these protected areas. Based on thematic maps of soil cover classification, elaborated for the years 1989 to 2008, with the purpose of analyzing the changes in the study area in this very period, the present work quantified the dynamics of the native flora in the interior and surroundings of the Area de Protecao Ambiental Estadual Cachoeira das Andorinhas and Floresta Estadual do Uaimii, located in Ouro Preto (MG). The results show that throughout the 19 years of comparison, the area occupied by the native flora remained the same with indices of 82 to 83% inside the UCs and 74% in its surroundings. With the results of the fragmentation, it is possible to identify the most critical areas or the greatest anthropic pressure and to direct specific programs, in the management scope, to minimize them.

Influência da expansão urbana nos movimentos em encostas na cidade de Ouro Preto, MG

Nowadays the city of Ouro Preto is faced with large problems relating to its expansion and urban increase, due to the lack of places with adequate geothecnical conditions for building. The city has been facing the consequences of inadequate occupation of the urban environment due to excessive inhabitation, lack of areas for urban expansion and the concentration of poor people around the rivers, brooks and the surroundings. Even in the central area, which is occupied by people with good social-economical conditions, the neglect of the risk of landslides is evident. This paper discusses this question, presenting in particular the problem of occupation of Morro do Curral hill.

Avaliação do perigo de queda de blocos em rodovias

Highway rock slopes are potentially unstable surfaces and as such are susceptible to rockfalls that affect the highways user safety, transportation infrastructure and surrounding environment. The geomechanical behavior of rock masses and also the geometric and traffic conditions of highways are fundamental aspects of rockfall evaluation. This research presents a case study of rockfall evaluation for slopes bordering highway sections, aiming to classify them and determine a hierarchy for intervention, based on defined criteria. In order to use this approach, field investigations including geomechanical classification of rock mass are necessary. In this context, twelve slope sections containing rock slopes in Espirito Santos road network were investigated. The slopes were analyzed individually and the influence of each parameter in the global rating was evaluated. Parameter effectiveness in the proposed method was also evaluated. The slopes were classified to define priority measures to minimize roadway problems in each place.

AVALIAÇÃO DA SUSCEPTIBILIDADE DE SOLOS GNAISSICOS À EROSÃO SUBSUPERFICIAL

The basement rock areas of the Maracuja hydrographic basin show great incidence of huge gullies. This work aims to investigate the influence of the underground erosive processes in the evolution of these features and to understand how the mineralogical and textural factors could affect soil erodibility, specially of the saprolites, since the lateric soils of this basin are more resistant to erosion. So, basic characterization and erodibility essays were carried out in representative soil samples. Soil susceptibility to piping and seepage erosion were investigated through current and modified pin-hole-essays. Laboratory physical models were used in order to observe these and other possible underground erosion mechanisms, especially the slides. However, piping erosion only occurs in the unsaturated portion of gully slopes, provoked by the concentration of superficial water, since pipes are not stable under total saturation, when their roofs tend to collapse, because of the low cohesion of these saprolites. In the other hand, slumps are very common in the saturated portion of gullies, affecting saprolites even in small and low declivity slopes.