SCOUR BELOW CAUSEWAY STRUCTURES

Abstract

There exists an obvious choice for bridging the natural channels by using a high level structure. However, often due to financial constraints and inadequate fund availability for road development, the engineer is forced to consider options like providing a cause-way in place of the bridge. Such crossings necessarily entail disruption in the existing traffic during high flood conditions. However, these structures are useful due to savings in the cost provided disruptions in the traffic are within a certain acceptable limits. There are various parameters that affect the hydraulic design of cause-way. Depth of scour is an important parameter that is needed for the design of foundations of the cause-way and its protection works. Generally Lacey's method is used for the determination of normal scour depth below high flood level as per Indian Road congress guidelines as no relationships specifically for determining the scour downstream of cause-way exist. Therefore, there is need for studying the phenomenon of scour downstream of cause-ways. In present study, an experimental investigation has been carried out concerning scour below a cause-way. The available equation for scour depth due to jet flow is found to satisfactorily estimate the scour depth occurring below the cause-way studied herein. However, the Lacey's method found in its present form is not found to be suitable for estimation of the cause-way scour.