Other than cost consideration, what problems will probably occur as a result of the following design? What methods might be used to overcome these problems?: A 2.5 thick fill is to be placed over a thick stratum of soft clay, then a one-story office building is to be built on the top of the fill. According to a settlement analysis, the weight of this fill will cause 600 mm of the total settlement over a period of 30 years. The differential settlement will probably be about 100mm. Although the building could be supported on spread footing foundations in the fill, the design engineer has decided to support it on a system of drilled shaft foundations that penetrate through the fill and into the underlying soils, thus insulating this building from the settlement problem.