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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]