Abstract
An existing cut slope on Highway RS-471/BR-153 is studied. The slope is composed of the Serra Geral Formation's material: a highly altered volcanic breccia and above it a slightly altered and very fractured rhyolite. A numerical analysis of the slope is carried out in two dimensions. Fracturing of the rhyolite necessitates the use of a constitutive model for materials with families of discontinuities (Ubiquitous-joint). To simplify the analysis of the problem and to examine some of the most sensitive variables, two more analyses are made, replacing the initial model by a Mohr's constitutive model, which considers the material as continuous. The results obtained from the Ubiquitous-joint model provide an acceptable representation of the field conditions, showing a failure mechanism type of rockfall from the face of the slope in the rhyolite, and the rupture surface of the breccia, without propagation of surface failure. In the analysis, when considering both materials as continuous, it is not possible to take account the fault conditions simultaneously, and this analysis also requires values of the mechanical parameters different from those recommended in literature.
Highlights
Numerical studies of slope stability, besides requiring good characterization of the materials involved, need prior knowledge about the possible mechanisms and situations that could lead the system to rupture
These authors describe cases where the level of fracture of the rocky mass is very high, in which structural control by the discontinuities may be less important than the overall conditions of resistance, which are capable of causing a rotational rupture, as is well known in homogeneous slopes formed by cohesive soil
To obtain a model that represents the current degree of fracture in the rocky mass, the Ubiquitous-joint model available in FLAC was applied
Summary
Numerical studies of slope stability, besides requiring good characterization of the materials involved, need prior knowledge about the possible mechanisms and situations that could lead the system to rupture. Analysis of slope stability using the limit equilibrium method, even though it allows consideration of different layers in each case, does not take account of the effect of excessive mass deformations or of the structural control by the discontinuities that occur mainly in rocky layers. These authors describe cases where the level of fracture of the rocky mass is very high, in which structural control by the discontinuities may be less important than the overall conditions of resistance, which are capable of causing a rotational rupture, as is well known in homogeneous slopes formed by cohesive soil. This work aims to obtain a single representative numerical model for the field conditions and those assumed in the study, through variations in the mechanical properties of the slope, as in the case of a continuous model
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