Design stability charts for construction procedure of basement walls using staged bermed excavation: a parametric study

The construction of basement walls using discontinuous staged berms is based on excavating the central zone of a lot and leaving a lateral berm – which is then removed in phases with unexcavated sections (buttresses) remaining until a concrete wall is completed in the excavated areas. It is a commonly used technique in many nations, but its use is unsupported by regulations or scientific studies. This paper addresses the need for a analysis of this technique and makes a study of the geotechnical parameters of the subsoils where it is applied, as well as the commonly used practices. The research involved over 4000 finite element method calculations integrating geotechnical parameters with construction geometry. The results have enabled the preparation of four stability design charts based on linear polynomial surface adjustment for two project scenarios: with and without surcharge load. This paper proposes the use of these stability design charts for staged bermed excavations in a broad spectrum of soil types and the incorporation of a designer-defined safety level to ensure temporary stability. Additional charts are provided to assess the safety factor of projects once the geometries and geotechnical parameters of the subsoil are known.