EFFECTS OF PILE DENSITY AND ARRANGEMENT ON FLOW CHARACTERISTICS AND SEDIMENT DEPOSITION AROUND A PILE-GROUP DIKE

抄録

Many pile-group dikes have been built along the banks of the Kiso River in Japan for several decades to control the riverbank erosion. However, flow and bed characteristics around pile-group dikes are not treated sufficiently, and no detailed explanation has been found in the literature. This study investigates the effects of different pile-group dikes on the flow and sediment deposition. Different numbers of piles per group, which was defined as pile density, with two types of pile arrangement, namely in-line and staggered arrays were compared. The results indicate that the pile-group dikes can reduce the velocity and enhance sand deposition in the downstream along the bank. Consequently, both can increase riverbank stability. A staggered case had a lower velocity and higher deposition along the bank than an in-line case with the same pile density. Furthermore, the staggered type significantly reduced the turbulence in the downstream. From an economic point of view, a lower pile density in staggered arrays can perform like a higher pile density in an in-line arrangement.