Abstract
Local scour is one of the key factors that cause the collapse of structures. To avoid structure failures and economic losses in water, it is usually essential to predict the equilibrium scour depth of the foundation. In this study, several design models which were presented to predict the equilibrium scour depth either under steady clear water conditions and combined waves and current conditions were recommended. These models from China, the United States and Norway were analyzed and compared through experiments. Moreover, flume tests for monopile foundation embedded in sand under different flow conditions were carried out to observe the process and gauge the maximum depth around the pile. Based on this study, for predicting the equilibrium scour depth around bridge piers, the computational results of three design methods are all conservative, as expected. For the foundation of offshore structures in marine environment, most of the predicted scour depths by design methods are different from field data; in particular, the mean relative error with these design methods proposed may reach up to 966.5%, which may lead to underestimation of the problem, overdesign and consequently high construction cost. To further improve the ability of the scour prediction in a marine environment, data from flume tests and some field data from a previous study were used to derive the major factors of scour. Based on the dimensional analysis method, a new model to estimate the equilibrium scour depth induced by either current or waves is proposed. The mean relative error of the new formula is 49.1%, and it gives more accurate scour depth predictions than the existing methods.
Highlights
Scour is recognized as one of the key factors that causes structure failures, which in turn leads to economic and life loss
The local scour depth on the model side was recorded with the help of scale pasted on the side of monopile model
Since the experimental working conditions are relatively few, in order to further analyze and evaluate the accuracy of local scour depth predicted with each equation, another 35 laboratory and 20 field data [6,18,31,32,33,34,35] were selected for verification
Summary
Scour is recognized as one of the key factors that causes structure failures, which in turn leads to economic and life loss. After investigation into the causes of damage to 143 bridges in the world, Smith [1] found that nearly 50% bridges were damaged due to water scour. In July 2013, the Panjiang Bridge in Jiangyou City of Sichuan. Province collapsed due to undermined pier foundation caused by flood scour (Figure 1). Structures in a marine environment suffer scour to different extents, which may endanger the stability of the structures. In September 2010, the ShengLi Well Workover Platform III of Chengdao Oil Field at Yellow River Estuary in Bohai. Sea collapsed due to the interaction of various factors, including scour (Figure 2).
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