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<br />7.5 f100dwalls
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<br />The purpose of floodwalls is similar to that of levees - to keep water out of an area. They
<br />are subject to hydraulic loading on one side with little or no earth resistance on the other
<br />side, Cantilever walls, cellular walls, buttress walls, and gravity walls are different kinds of
<br />f100dwalls shown in Figure 7.16. Possible modes of failure for floodwalls are overturning, slid-
<br />ing, or failure of underlying soil. If competent rock formations are present, the floodwall
<br />should be keyed into the rock for extra protection against failure.
<br />
<br />Cutoffs and drains should be provided to carry away any significant amount of seepage.
<br />However, the presence of drains should not lessen the design for uplift pressures. Also, drain
<br />pipes should not be placed directly under the base of a floodwall.
<br />
<br />Two general application guidelines will be mentioned here. Gravity walls are most approp-
<br />riate for low, lightly loaded walls, They are easy to design and construct, but the large
<br />volume of concrete can become a prohibitive factor in economic considerations for large
<br />heads of water. The cantilever wall is a more complex design, but requires much less con-
<br />crete, It is suitable for many situations, especially where a moderately high wall is needed.
<br />The cantilever wall's base may be supported on drilled piers or piles if soil conditions are
<br />very poor. A final point in the design of this kind of floodwall is freeboard. The freeboard
<br />requirement depends on whether a single structure is being protected or a big area of a
<br />community. Freeboard requirements were given in Table 7.1, The design and construction of
<br />floodwalls should only be done with experienced, professional engineering direction.
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<br />Figure 7,16, Floodwalls, (Reference 8)
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