Seepage and Boiling around a Sheet Pile under Different Experimental Configuration

The sheet piles are used below hydraulic structures to reduce seepage flow rate and hydraulic gradients at the outlet of such structures that are rested on the permeable foundations. Up to now, for analysis of seepage under hydraulic structures, a number of research works have been conducted in the form of numerical models. However, less field and laboratory works have been done to study the boiling phenomenon for the evaluation of the numerical models. In the present research work, a laboratory model was made to simulate seepage flow and its behavior downstream of a sheet pile under vertical and inclined configurations. The model consisted of a flume 2.2 m long, 0.8 m deep, and 0.4 m wide, in which vertical and inclined sheet piles were provided by cast acrylic sheet. The flume was made of steel frame and Perspex as well as thick glass sheets. Fine clean sand was used as an alluvial foundation and then compacted to a uniform density at the bottom of 40 cm of flume. Perspex sheets were used as sheet pile variable depth. The piezometric heads were measured both downstream and upstream of the sheet pile using small-diameter clear plastic tubes. The results indicated that the optimal ratio of sheet pile depths for both vertical and inclined sheet piles to reduce boiling under maximum upstream water level were $d/D=0.44$ and $d/D=0.34$, respectively. Finally, it could be concluded that the inclined configuration with the angle of 60° (to the horizontal direction) performed well to reduce boiling compared with the vertical case.