Control of Seepage Flow
When the general ground as well as the impervious strata below are slopping, seepage
flow is likely to exist. If the seepage zone is at depth less than 0.6 to 0.9 metre from the
Subgrade level, longitudinal pipe drain in trench filled with filter materlal and clay seal
may be constructed to intercept the seepage flow. Figure 11.7 shOws the method by
which the seepage line can be lowered to the desired depth.
Control of Capilary Rise
If the water reaching the subgrade due to capillary rise is likely to be detrimental, it is
possible to solve the problem by arresting the capillary rise instead of lowering the eater
table. The capillary rise may be checked either by a capillary cut-of of any one of the
following two types
(i) A layer of granular material of suitable, thickness is provided during the
construction of embankment, between the subgrade and the highest level of subsurface
water table, (See Fig. 11.8). The thickness of the granular capillary cut-off layer should
be sufficiently higher than the anticipated capillary rise within the granular layer so that
the capillary water can not rise above the cutoff layer.
(ii) Another method of providing capillary cut-off is by inserting an impermeable or a
bituminous layer in the place of granular blanket. (See Fig. 11.9).
