SOME ASPECTS OF 3-DIMENSIONAL PRESSURES UNDER HYDRAULIC STRUCTURES IN HIGH GROUND WATER TABLE REGIONS

Abstract

Effect of providing sheet piles below the upstream or downstream half of the main wing call and extension of the usual cut-offs at the end to different lengths under the return wings on pressure distribution underneath the floor of the hydraulic structure and along the dotnstream face of the downstream end cut-off o for. the to different high ground eater table elevations viz. H above tail water levolg and 0.511 above tail eater level$ has been investigated on a 3 imwnsional electric analogue model. similar combination of piles has been tried both at upstream and downstream of the structure. Cross variation of pressures on the floor and on the do tnstream Paco of the cut-off has been observed. 2-Dimoncional seepage pressures for the sawe dimensions of the floor and cutoff have been evaluated from Khosla'o curves and theoretical Analysis. It has boon concluded that the provision of piles in the upstream portion in general is batter for reduction of uplift on the up stroau half of the floor. It is also found that proportionato advantage will not be gained by the extension of the pile belowr return wing !gall to a larger length over 12.5 percent length of the floor or so.