OS PARÂMETROS DE RESISTÊNCIA AO CISALHAMENTO E A ESTABILIDADE DAS ENCOSTAS NO PLANALTO DE PARAIBUNA E SERRA DE CARAGUATATUBA

Abstract

The central aim of this work is to confront spatial behavior of shear strength parameters of soil and regolith materials at Paraibuna Plateau, with those of Caraguatatuba Scarps. The behavior of slope stability and its correlated variables in the soil-regolith transition along slope profiles was evaluated, for granite, migmatite and micaschist parent materials. For this propose, we had making measures of shear strength for residual soils and regolith materials with soil "Cohron Sheargraph" apparatus and evaluated the shear stress tension behavior at soil-regolith boundary along slope profiles, in each environment and lithology. When we compeer the results for the two areas, a compensation mechanism appears. At Paraibuna plateau, the major part of the shear resistance is attributed to cohesion, when at Caraguatatuba scarps is the friction angle the major strength component. An important question here is the change of soil bulk-density variable along slope profile evolution, because the intense clay production, mainly Kaolinite and Gibbsite at B and C-horizons, in the plateau tropical environment. We detected too, at threshold conditions, that slight change in soil bulk-density may changes drastically the equilibrium of stress-strength tensions at potential rupture surface with its consequent loss of stability and landslide event production. At Caraguatatuba scarps, the extremely humid environment would dissolves Kaolinite and promotes the shut down of cohesion.