How Much Is Too Much? A Case Study of Excavation-Induced Building Settlement

This paper presents a case study of building settlement resulting from an adjacent deep excavation (approximately 5 ft away and 40 ft deep). The settled structure was a multi-story brick building, which leased residential and commercial space. The excavation was supported by steel sheeting and three levels of internal steel bracing. Many aspects of the temporary excavation support system were prescribed in the specifications, including the size of the sheeting, embedment of the sheeting, number of bracing levels, elevation of bracing, and the magnitude and location of the adjacent structure loads. The building was monitored by survey points before, during, and after construction, and lateral movement of the sheeting was measured by inclinometers and survey points. During construction, the maximum lateral movement of the sheeting in front of the structure exceeded the limiting value set by project specification, and due to the proximity, the settlement of the adjacent structure was approximately equal to the lateral movement of the sheeting (causing architectural damage to the structure). This paper discusses the formation of expectations and communication of risk with project stakeholders and provides recommendations for future project planning.