This paper presents monitoring results from a deep supported excavation in central Oslo, Norway. Sheet pile walls and tensioned tieback anchors drilled into bedrock supported the excavation in soft low sensitive clay to a depth of about 9 m. In two specific areas, relatively large settlements were observed, coinciding with drilling of anchors for the sheet pile wall. The immediate subsidence during drilling was followed by a period of ongoing settlements at a lower rate. These ongoing displacements were not expected as pore pressure reduction alone could not explain the rate or extent of displacements measured. Immediate subsidence during drilling was largest in areas with sandy and silty layers and is related to erosion and loss of soil volume due to excessive flushing and remoulding of soil during drilling. The observed mechanisms are characteristic for deep excavations in Norway and the collected data inform further work to reduce ground displacements caused by excavation works.