Forensic Investigation of a Slurry Wall Failure: A Case Study

The use of numerical modelling in solving geotechnical problems has significantly increased in the past two decades due to its widespread acceptance by geotechnical engineers and the rapid growth in computing power. In this work the failure of a slurry wall system which was the subject of a dispute between two contractors is investigated. The failed slurry wall was part of an excavation shoring system for a power plant intake structure in Australia. The construction sequence provided by the wall designer/contractor was not followed by the main contractor. The slurry wall failed and resulted in flooding of the excavation and significant ground deformations. This was followed by extensive and costly remediation works. The main contractor believed that the adopted construction procedure was not responsible for the failure, but its inadequate design was. This paper presents the methodology and results of modelling undertaken of the slurry wall installation to determine the magnitudes of induced stresses and displacements in the wall as a result of the adjacent excavation for two scenarios, “as designed” and “as constructed”. The analysis was carried out utilizing the FLAC 2D program (Itasca group) for a plane strain case, and its built-in elastic-plastic Mohr-Coulomb stress-strain model.