Earth retaining solutions and façades underpinning for the refurbishment of a historic building in Lisbon

Abstract

This article describes the excavation, earth-retaining, and façade underpinning solutions adopted during the rehabilitation of Palácio do Lavra and Palácio das Pedrosas, a 260-year-old building located in Lisbon. The intervention aimed to construct new basement levels beneath the original foundations, requiring the development of temporary underpinning solutions to allow the safe execution of the underground floors. The project presented significant challenges due to the complex geological and geotechnical conditions of the site, as well as its location in the historic city centre at the base of a slope and within a dense urban environment. The peripheral earth-retaining system consisted of a king post wall solution, temporarily supported by ground anchors, tie rods, and steel struts. Façade underpinning was carried out using tubular micropiles with different diameters, which were also used, whenever possible, as temporary vertical support for the retaining wall panels. This article presents the main constraints that formed the basis for the design of the adopted solution, as well as the calculation models used and the adaptations implemented during construction in response to unforeseen site conditions and instrumentation results.