Numerical Analyses Of The Influences Of Scour On The Vertical Bearing Behavior Of Single Pile Foundations For Bridges

Scour is a process of soil erosion, which can occur around the foundations of bridges caused by flowing water, it can, therefore, reduce the capacity of the foundations and sometimes lead to the failure of the bridges. Failure of bridges due to scour had motivated many researchers to explore the causes of scour and to predict the maximum scour depth at piers, in which, however, limited ones had considered how to evaluate the effects of scour on piles under bridges. Therefore, this paper lays emphasis on vertical bearing behavior of pile foundations under scouring conditions.Based on the finite element model established with ABAQUS, the excavation method were used in the researching process of numerical simulation of fluid scour. The main work and results are summarized as follows.Firstly, during an analysis of scour effects on vertically loaded piles, scour effects were considered by simply removing the whole soil layer to the scour depth previously. In this paper, however, scour pit geometry is not ignored, in other words, the width and slope of scour pit are considered. The computed results indicate that scour depth is the most influential factor in the pile scour response compared with width and scour slope.Secondly, to gain more understanding of scouring effects on the vertical capacity of the piles embedded in sandy soil, factors such as soil stiffness and pile slenderness ratio were studied to show their effects on the percentage decrease of vertical load capacity of single pile foundations under scouring conditions. As the result shows, the PDV values due to scour are higher for the piles in dense sand than those in loose sand, and the PDV values of piles in loose sand reaches almost 50% when the scour depth reaches 8 times the pile diameter. The decrease in vertical load capacity due to scour is more serious for short piles. Increasing pile diameter is good for diminishing the declining trend of vertical load capacity of piles due to scour, which, however, is not so obvious.Thirdly, the scour depth was studied to show its effects on the distribution regulations of axial force and lateral frictional resistance of piles under scouring conditions.The basic understandings of scour effects on vertical bearing behavior of single pile foundations under scouring conditions have been gained in this paper, which lays the foundation for evaluating the safety of bridge subjected to fluid scour and the improvement of design theory of the pile foundations.