Braz. J. Aquat. Sci. Technol., 2005, 9(1):31-37. 31 INTRODUÇÃOA zona costeira do Rio Grande do Norte possui grandes belezas naturais, destacando-se no litoral oriental sul a praia de Pipa, situada no Município de Tibau do Sul, com suas exuberantes falésias. Atualmente, esta praia está sendo afetada por processos erosivos em conflito com a atividade turística local em expansão. Tal fato, aliado à pressão econômica da ocupação imobiliária provoca sérios impactos ambientais, uma vez que o ambiente costeiro é delicado e frágil, e qualquer mudança que o atinja provoca alterações em todos os fatores naturais envolvidos.Um dos problemas relacionados à expansão do turismo local é a ocupação irresponsável da borda das falésias, que aliada à erosão costeira (avanço da linha de costa na direção do continente) vem ocasionando diversos problemas, tanto aos proprietários da terra, quanto ao poder público e à natureza.O litoral potiguar é caracterizado, de maneira geral, por praias arenosas interrompidas por falésias e arrecifes de arenitos, paralelos e próximos à praia. Especificamente na zona costeira da praia de Pipa estão ocorrendo mudanças nas feições da costa por causa da ação das ondas e das intensas precipitações pluviométricas. Esta zona fica entre as pontas do madeiro e da pedra do moleque (Figura 1), possui aproximadamente 5 km de extensão e sua formação é predominantemente de falésias.Em alguns trechos, essas falésias vêm sofrendo sucessivos recuos, devido à ação do mar e da água das chuvas. A erosão costeira nessa área é motivo de várias pesquisas e trabalhos científicos, cuja importân-cia reside no fato da movimentação turística na região ser muito intensa. O ecoturismo praticado em Tibau do Sul é um dos que mais se desenvolvem no Brasil, segundo dados da Secretaria de Estado do Turismo do RN (Rio Grande do Norte, 2003).Dentro deste contexto, as ações antrópicas aliadas aos processos erosivos naturais são fatores preponderantes no equilíbrio ambiental da região. Sendo assim, é de fundamental importância identificar tais processos naturais vigentes (no caso do presente trabalho, a erosão costeira), a fim de subsidiar o entendimento da capacidade de suporte do meio às atividades humanas desenvolvidas na região. Processos erosivos e movimentos de massas em encostasAs feições morfológicas que compõem a paisagem do planeta foram e são continuamente esculpidas por agentes modeladores externos desde milhares de anos atrás. Entre estes agentes, os mais importantes são: as chuvas, as marés e os vários tipos de intemperismo. A ação deles é geralmente no sentido de tornar o relevo plano. Contrapondo-se a essa ação, tem-se a resistência dos materiais que compõem as superfícies naturais. Quando os agentes modeladores externos atuam com intensidade superior à resistência dos materiais que formam uma encosta, podem ocorrer processos erosivos ou movimentos gravitacionais de massa. However, this beach is being affected by erosive processes in conflict with the local tourist activity, which is in expansion. Such fact ally to the e...

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A região costeira do Estado do Rio Grande do Norte (RN), no nordeste do Brasil é constituída por materiais sedimentares que formam tabuleiros costeiros, dunas, falésias e praias arenosas. A exuberância paisagística dessa área representa um atrativo para a ocupação humana e desenvolvimento de atividades turísticas. Esse processo de urbanização potencializa a ocorrência de movimentos de massa nas falésias, resultante doaumento da carga no topo das falésias, remoção da vegetação e aumento da erosão superficial. Estudos anteriores desenvolvidos nas falésias da região indicam que a linha de costa se encontra em processo de recuo, o que põe em risco a infraestrutura instalada e seus usuários. O presente artigo visa compreender os mecanismos de movimentos de massas que ocorrem nas falésias e resultam no seu recuo. O trabalho sistematiza as informações existentes, adiciona observações de campo e propõe um modelo conceitual contemplando os mecanismos de ruptura e processos erosivos identificados, ao longo da porção sul do litoral Oriental do Estado do Rio Grande do Norte. Os principais mecanismos identificados estão diretamente relacionados à erosão superficial em episódios de chuvas intensas, umedecimento do material e a erosão basal, caracterizada pela remoção de material do pé das falésias, devido a ação das ondas.

Deep mining operations require special measures in order to keep safe and economic aspects. After mine ore is extracted, voids are created and need to be filled with high-strength, low-cost materials. Cemented Paste Backfill (CPB) has recently become one of the main alternatives in filling stopes. Although numerous papers have mentioned the magnitudes of the strength of this material, its behavior under high confining pressures is still not well understood. Therefore, the purpose of this study is to increase the knowledge regarding the CPB behavior. Triaxial compression tests were performed using a Hoek Cell and Load Frame System under high confining pressures. Samples with two different binder contents were used in order to obtain the CPB strength improvement. Besides the self-weight consolidation curing method, samples were subjected to a different curing method that simulated a zero gravity condition (rotating wheel) in the first curing day to compare their mixture properties. The results suggested that both curing method and binder content have influenced the geomechanical properties of Cemented Paste Backfill. By increasing the curing time, the CPB shear strength has increased slightly, whereas specimens with higher binder content presented a significant increase in shear strength values.

Landslides are part of the natural processes of Earth’s surface dynamic, which could be accelerated or triggered by anthropic interference. Inadequate occupation of areas highly susceptible to landslide processes is the principal cause of accidents on Brazilian urban slopes, especially those occupied by settlements and slums. In Natal, Rio Grande do Norte state, Brazil, the existence of areas with steep and densely occupied slopes makes the municipality susceptible to landslides. In this context, the present study aimed to map the risk of landslides in an urban area located in the city of Natal. Using the quali-quantitative model proposed by Faria (2011), adapted for the conditions of the study area, which applies a multicriteria analytical hierarchy process (AHP) to a Geographic Information System (GIS), 11 risk indicators were submitted to pairwise comparisons by 10 risk management specialists in order to determine the relative importance (weighting) for each of these factors as a function of their contribution to the risk. The weightings obtained were combined to produce the final risk map of the study area, using a map algebra framework. The results show the existence of a critical risk for the resident population, primarily related to the possibility of a landslide, with potentially negative economic, environmental, and mainly social impacts.

Many slope failures in residual soils have been attributed to increased soil pore pressure. During the rainy season, water infiltration occurs, which can lead the slope to rupture by increasing the pore pressure. However, some landslides have been observed with pore pressures below those required for failure. Hypotheses for such ruptures include the occurrence of creep or fatigue due to cyclic variations in the piezometric level on the slope. This paper presents a study on the effect of pore pressure on the behaviour of the residual soil of the Soberbo hillside in Rio de Janeiro, Brazil, subjected to monotonic and cyclic pore pressure. Triaxial tests that simulate the increasing piezometric level (constant shear drained-CSD tests), drained creep (DC-CSD tests) and cyclic pore pressure variation (CPP tests) in slopes were carried out. The CSD test results showed that the failure due to increasing pore pressure is essentially dilatant and confirmed the peak strength obtained from conventional drained triaxial tests. Sudden failure was observed in all CSD tests at the end of the pore pressure increase phase. The results show that the failure of the slope may occur due to drained creep and the loss of soil shear strength under cycling pore pressure.

The methodologies used to calculate piled raft foundations are normally more complex than conventional foundations due to the large number of variables involved in the problem. In the conventional block, the interaction variables considered are only between the pile and the soil. In the piled raft, all the interaction effects must be considered, as follows: plate-soil, plate-piles and piles-soil, simultaneously. The Finite Element Method (FEM) has proven to be a useful tool in analyzing these types of problems. This study aims at assessing the behavior of piled rafts using the Cesar-LCPC numerical tool, version 4.0, which is based on the finite element method. Literature cases of rafts supported by 9, 15 and 16 piles were analyzed. The results obtained were compared with analysis methods presented in the bibliography. The following parameters were assessed: relative spacing (S/D), relative length (L/D), relative stiffness between piles and the soil (KPS), and settlement of piles and the raft. The spacing between piles has a significant influence on load distribution between piles and the raft. Very small spacing provides stiffness to the foundation, which then functions as a conventional pile foundation, in which only the piles absorb the load from the superstructure. The larger the L/D ratio, the lower the settlement and for a given modulus of elasticity of the pile, the increase in relative stiffness (KPS) causes an increase in settlement. In all analyses, the data obtained corroborated the results presented by other methods published in the literature.

The aim of the present study is to assess the incorporation of kaolin processing waste as partial substitute for aggregates in asphalt concrete. Mixtures elaborated from the conventional mixture with the gradual incorporation of kaolin processing waste (5 to 40%) were evaluated by volumetric composition, mechanical behavior and susceptibility to moisture tests, obeying current Brazilian norms, according with international standards. The results show that the coarse kaolin waste displays grains with varying diameters, and, as such, can substitute part of the conventional aggregates and filler used in an asphalt mixture. Moreover, its mineralogical composition showed the same minerals in the composition of conventional aggregates used in paving. The assessment of the mechanical behavior of these mixtures indicate that the increased waste levels in the mixtures studied caused an increase in stability and a reduction in tensile strength. When susceptibility to moisture was considered, the results indicate that up to 25% of residue can be used as a substitute for conventional aggregates.