EFFECT OF LEAKY SHEET PLIES ON EXIT GRADIENT

Abstract

Although most of the old Barrages and Weirs constructed on permeable foundations without taking account of leakage through piles, in their design, have stood the test of time, yet the effect of leakage through sheetpiles needs consideration. Specially in view of the e- findings that this phenomenon leads to the con,entration of flow lines and might adversely effect the exit gradients. The effect of the leakage through the downstream sheetpiles has been studied and discussed in this thesis. The experimental results have been analysed and presented to bring out the effect of different S/L ratios,different percentages of leakage and depression on the pressure distribution on both the floor and downstream face of the downstream cutoffs and also on the resulting exit gradient. The study reveals that there is definite increase of pressure throughout the downstream face of the downstream sheetpile due to increase in leakages with consequen increase in the exit gradient as compared to the solid cutoff and that there is decrease of pressures below the floor. There is increase of pressure below the floor with the increase of S/L ratio i.e. with the increase of depth of cutoff. The effect of depression is just the opposite i.e. there is decrease of pressure below the floor with the increase in d/L ratio although the pressures e —ef-fe4 on the downstream face of the downstream sheetpile are not appreciably affected.