Old Problem Requires Innovative Investigation Geotechnical Investigations of the Chippawa Power Canal Culvert Foundation

摘要

Highway 420 crosses over the Chippawa Power Canal in Niagara Falls, Ontario supported by a large 22m span concrete culvert structure. The culvert, founded on dolostone bedrock and covered with 16 m of backfill, has experienced some displacements along some of the culvert sections. Significant deterioration of the canal walls above the water level has also been observed. The walls below water could not be visually assessed. The observations raised questions regarding the stability of the culvert and a geotechnical investigation was initiated to determine the causes of the culvert displacements and the rock wall deterioration and to assess the risk to the highway. A major challenge in undertaking the geotechnical investigation was that the power canal had to be kept in service during the investigation. The rapid flow rate and the fact that the canal walls were partly under water did not allow direct access and necessitated a variety of investigation methods. Three state-of-the-art investigation methods were applied: 1) an extensive borehole investigation, 2) a LiDAR survey to investigate the canal walls above water level, and 3) an underwater Sonar survey focused on the walls below water. The methods had to be compatible to combine the three data sets into one single model. The resulting integrated model will allow for a comprehensive stability analysis and assessment of the wall conditions and will consequently enable the determination of appropriate remedial measures.