Forensic Engineering Assessment of the Failure of a Temporary Sheet Pile Wall

ABSTRACT: A case history documenting the failure of a temporary sheet pile shoring wall at a wastewater treatment facility expansion project is presented. The wall was designed to retain a height (H) of 6 m of soils overlain by 3.8 m high sloping ground behind the shoring. The wall was designed as a cantilever system without secondary supports such as tiebacks and struts, and with nominal embedment depth (D) yielding an H/D ratio of only 0.5. The subsurface conditions consisted of topsoil and fill overlying loose to compact gravelly sand and silty sand, with groundwater levels at a depth of 1 to 1.5 m below ground surface. The cause of failure can be attributed to inadequate embedment of the shoring wall leading to overturning failure, lack of secondary lateral supports as well as inadequate flexural capacity of the sheet pile sections. The failure reinforces the importance of adhering to fundamental principles of geotechnical engineering in the design of excavation support systems and the necessity of geostructural expertise in shoring design for interpreting the results of design analysis. The case history serves as another example of the general lack of attention to the design of temporary works in the industry despite the risk of severe consequences associated with failures.