Design of Structures With Intermediate Filters

Until now no solution was available to determine the effect of plane drainage located anywhere between two end cutoffs of a flat floor founded on permeable soil of finite depth. An exact solution has been obtained using conformal mapping. Equations for uplift pressure below the floor and for exit gradient are given. The equations are solved numerically to obtain pressures at key points and at the exit gradient. The results are given in the form of easy‐to‐use design curves. The uplift pressures reduce considerably along the structure's entire profile with the provision of filtering even very small lengths. The uplift pressure, in general, decreases on the downstream side and increases on the upstream side as the filter is moved from upstream to downstream. The uplift pressure decreases along the floor, except along the upstream cutoff, with decreases in pervious soil strata depth. The uplift pressure increases all along the floor with increases in depth of downstream cutoff. The exit gradient decreases with increases in depth of downstream cutoff and decreases in pervious soil strata depth.