Geotechnical Issues Associated With the Design and Construction of the Middle River Bridge

The existing short single span, single lane, concrete bridge constructed in 1930 across the Middle River in the Town of Mc Kellar, Ontario required replacement as a result of age and sub-standard approach roadway geometrics. In 1986, a geotechnical investigation was undertaken to upgrade the existing bridge. This investigation was undertaken primarily within the river since the new bridge structure was contemplated on an alignment with improved geometrics. The proposed structure was designed but was never constructed. In 2009, the need for a new structure was revived with the idea of placing it on the existing alignment with minor alignment modifications. However, as a result of buried timber being encountered during the geotechnical investigation, conventional drilling had to be abandoned and an air track rig used to ascertain the nature of the subsurface conditions. Thirty two (32) probe holes/boreholes were undertaken to define the preferred location of the new abutment piles. During bridge construction, the designed batter piles slipped along the steeply dipping rock surface at the west abutment and had to be retained by a massive deadman anchor. This paper addresses the issues encountered and concerns raised during the geotechnical investigations and how these were addressed and resolved. This site although small exhibited challenging ground conditions resulting from the lack of historic evidence, physical constraints imposed on the geotechnical investigation by the river and surroundings, and overall expenditures

Full-Scale Load Testing of 57-Year Old Raymond Piles for Foundation Re-use

The proposed reconstruction of a demolished coke battery superstructure of a steel mill to a level higher than originally constructed in 1952 required the evaluation of the geotechnical resistance and settlement characteristics of its existing foundation piles. Except for design drawings showing the layout of the substructure elements and the borehole logs, there were neither as-built drawings nor any records available about the design and construction of the piles. A total of nine (9) axial compressive load tests were initially undertaken. Two (2) 19 ft long piles were initially tested under the pusher tracks, and a further seven (7) piles of varying lengths under the foundation of the coke batteries. These piles were assumed to have been installed into hard clay till underlying the site. The load tests showed that the mandrel driven outer steel casing and concrete in-filled piles could accommodate a load of 90 tons with minimal settlement. Cylindrical cores of the pile concrete taken following the load testing provided compressive strengths varying from 46 to as much as 62 MPa. This case study provides details of the excavation and dewatering issues, load test set-up, and the difficulties encountered in assessing and testing old foundations for re-use in a confined underground environment. It is hoped that this case study and its findings will encourage the proper assessment and evaluation of existing foundations as this could result in considerable savings in superstructure revitalization, emphasize the need to maintain design and construction records, and to instrument and monitor important foundations for long term reuse