A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Murphy Creek Flood and Scour Study
A large flood occurred on Murphy Creek, in Wyoming, on August 27, 2002. Using the 1987 U.S. Geological Survey regression equations, the 100-year flood for the study site was estimated by WYDOT to be 6,750 cubic feet per second (cfs), and the 500-year flood was computed to be 14,000 cfs. An approximation of this large flood discharge at Murphy Creek by WYDOT using a depth of 27 ft indicated a discharge of approximately 20,000 cfs, well in excess of the 500-year frequency. Water surface profiles were computed for discharges of 3,420, 6,750, 14,000 and 20,000 cfs. These profiles indicated that the flow passes through critical depth and a large drop in the energy grade line occurs from the downstream face of the downstream bridge. The large drop in energy at the exit section is indicative of the potential erosion power at the downstream side of the bridge. Abutment scour equations are based on the approach flow conditions at the upstream face of the bridge; they do not effectively estimate scour of the abutment at the downstream expansion that occurs under choking conditions. Appreciable amount of energy losses due to contractions can be encountered for flows under choking conditions. A limit opening ratio equation was derived from the principles of energy conservation and continuity and accounts for the critical flow conditions in the contraction and the energy losses caused by severe contractions. The energy loss coefficients are developed based on a total of 186 sets of choking experiments. Using computer modeling, the WYDOT Bridge Program will use the results of this research in predicting the limits of anticipated scour and the design of scour countermeasures at sites having complex hydraulic conditions such as those at Murphy Creek.
Murphy Creek Flood and Scour Study
A large flood occurred on Murphy Creek, in Wyoming, on August 27, 2002. Using the 1987 U.S. Geological Survey regression equations, the 100-year flood for the study site was estimated by WYDOT to be 6,750 cubic feet per second (cfs), and the 500-year flood was computed to be 14,000 cfs. An approximation of this large flood discharge at Murphy Creek by WYDOT using a depth of 27 ft indicated a discharge of approximately 20,000 cfs, well in excess of the 500-year frequency. Water surface profiles were computed for discharges of 3,420, 6,750, 14,000 and 20,000 cfs. These profiles indicated that the flow passes through critical depth and a large drop in the energy grade line occurs from the downstream face of the downstream bridge. The large drop in energy at the exit section is indicative of the potential erosion power at the downstream side of the bridge. Abutment scour equations are based on the approach flow conditions at the upstream face of the bridge; they do not effectively estimate scour of the abutment at the downstream expansion that occurs under choking conditions. Appreciable amount of energy losses due to contractions can be encountered for flows under choking conditions. A limit opening ratio equation was derived from the principles of energy conservation and continuity and accounts for the critical flow conditions in the contraction and the energy losses caused by severe contractions. The energy loss coefficients are developed based on a total of 186 sets of choking experiments. Using computer modeling, the WYDOT Bridge Program will use the results of this research in predicting the limits of anticipated scour and the design of scour countermeasures at sites having complex hydraulic conditions such as those at Murphy Creek.
Murphy Creek Flood and Scour Study
A. Molinas (author) / W. Bailey (author)
2004
64 pages
Report
No indication
English
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