ABSTRACT

Barbosa, N.; Taquez, D.; Santos Jr, O.; Freitas Neto, O.D., and Scudelari, A., 2020. The effect of basal erosion on sea cliff stability. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 362–366. Coconut Creek (Florida), ISSN 0749-0208.

Coastal areas attract substantial interest from the general population, and development is quite common in these regions. Therefore, it is necessary to study coastal erosive processes to provide a better understanding of the factors that influence the stability of sea cliffs and consequently their safety. In this paper, two typical cliff profiles were studied: a vertical cliff section and another with a lower slope. Both profiles are representative of slopes existing on the northeastern coast of Brazil. Basal incisions of 1 m, 2 m and 3 m were evaluated. The cliffs considered are not subjected to anthropogenic activities, and thus, only natural conditions influence their stability. The stability of the cliffs was investigated through a comparative analysis between the tensile stresses acting on the slopes and the tensile strengths of the materials considered. For the cliff with a lower slope, it was verified that the tensile stresses obtained presented low values, whereas in the vertical cliff, the tensile stresses were significantly higher. The main mechanism responsible for triggering instability processes is the partial increase in the degree of soil saturation caused by rainfall, which decreases the soil strength and triggers landslides. From the tests carried out, it was observed that the cohesion intercept of the saturated soils is approximately 26% of the value obtained for the soils with natural moisture content. However, the angles of internal friction in both cases suffer negligible variations. The study of the stability analysis presented in this paper effectively represents the types of failures observed in cliffs on the Brazilian coast. The analysis by tensile stress is much more coherent than the failure surfaces obtained by traditional methods of analysis.

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