CASE G3 (continued)
Collection of Facts: Upon inspection of the site, it was apparent that an
upwards force had caused the failure. A geotechnical evaluation revealed a
water table close to the ground elevation. However, the tank was designed
without consideration of the uplift force due to hydrostatic head. Therefore,
no provisions for anchorage of the bottom were made.
Solution: One of the most critical loading conditions of any structure below
the water line is hydrostatic pressure. This pressure is applied on the side
of the structure as well as upwards on the bottom. Various solutions were
taken into consideration. The basic elements included gravity weight and an
anchoring system to counteract the uplift and a method to repair the buckled
plate. The most cost effective and reasonable solution was to provide a
concrete slab anchored to the bottom of the tank (See Fig. 2).