Effectiveness of combinations of raft foundation with aprons as a protection measure against bridge pier scour
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Scour around bridge pier is the main reason for the failure of bridges. The local scour around the pier causes exposure of the foundation and may lead to undermining of the structure. Different types of protection measures such as the provision of raft, apron, sheet piles, etc. can be used as scour protection measures. One of the possible effective bridge scour protection measures is to provide a raft foundation with cut-off walls and provision of flexible stone aprons towards upstream (u/s) and downstream (d/s) sides of the pier. In this study, the effectiveness of various bridge pier scour protection measures using raft and aprons is investigated through hydraulic model studies in the laboratory. The results are compared for various cases, such as a simple pier, pier with raft and extended raft, pier resting on a raft with stone aprons at u/s and d/s of the raft and pier resting on an extended raft with stone aprons on u/s and d/s of it. The comparison of various cases showed that rigid raft with stone aprons on u/s and d/s and extended raft with apron are found to be more effective in reducing immediate scour beyond the rigid raft, thereby giving protection to the bridge piers.
KeywordsScour pier raft foundation stone aprons scour protection physical model study
Authors are thankful to the Ministry of Road Transport and Highways (MORTH) for sponsoring the project titled “Hydraulic Model Investigations for Design of Raft Foundations for Bridges (B-40)” and the Director General, Chief Engineer, Superintending Engineer and Executive Engineer for co-coordinating the project. We express our sincere gratitude to Shri P L Bongirwar, Former Secretary, Maharashtra PWD, and Late Prof. U C Kothyari, Indian Institute of Technology Roorkee, for all the suggestions, help and support provided during the initial stages of this study. We are also thankful to the former and present engineers of Maharashtra PWD (Shri R.R Chonkar, Shri J. T. Nashikkar, Smt. Sanjivani Nigade Saha and others) and the staff of Hydraulics laboratory, IIT Bombay, for their untiring support and help rendered during model preparation and testing.
Funding was provided by Ministry of Road Transport and Highways (MORTH) , New Delhi (Grant No. 09MORTH001).
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