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There is a fault in the region of Niteroi city, Rio de Janeiro, Brazil, and weathering has formed different soil layers in terms of granulometry, resistance, and stiffness, which are regularly spread throughout the soil mass. These reasonably continuous reliquiae soil layers showed thicknesses varying from a few millimetres to few centimetres. For the weak soil layers, laboratory tests indicated the presence of high activity clay minerals and low shear resistance parameters. The present paper numerically assesses the impact of those relatively weak layers and the excavation execution procedure on the performance of anchored walls. The direction of those layers was orthogonal to the wall face, and the dip was unfavourable to the excavation. The numerical modelling was firstly validated against data from an instrumented structure excavated in gneiss residual soil located in Niteroi city, Rio de Janeiro, Brazil. The results of the parametric study show that the weak layers plastify during the excavation with low lateral movements and the presence of those weak layers leads to an increase of the uphill settlements (about six times), lateral facing displacements (about four times), distortions (about 12 times), and anchor loads (about 1.4 times). This research calls attention to the importance of reliable site investigation for determination of the soil profile and its correct modelling in order to have a safe and cost-effective project. [ABSTRACT FROM AUTHOR]

Previous studies have indicated that many rock slope failures in Rio de Janeiro, Brazil, occur during relatively dry periods when there is little, if any, rainfall. In the present paper, we describe these events and propose possible mechanisms for their occurrence. It is believed that daily fluctuations in temperature may create thermally induced stresses of enough magnitude to propagate fractures already existing in the rock mass. Laboratory experiments were conducted in order to measure temperature variations in a fractured rock system. Using the experimentally obtained data, we carried out numerical analyses in order to verify whether temperature-related stresses were indeed able to propagate fractures existing in the rock mass. The results obtained indicate that cycles of temperature change over time, especially during the colder months of the year can indeed create stress conditions in the rock mass able to propagate existing non-persistent joints, and ultimately lead to failure of the rock slope. [ABSTRACT FROM AUTHOR]