ABSTRACT
The causes of severe cracks on lightly loaded buildings within the Sokoto Rima River Basin Development Authority Heaaquarters Complex have been found to be due to inadequate foundation aesign. The soil within the complex is founa to be predominantly Reddish Brown Well Graded Clayey Gravel exhibiting collapsing characteristics. The soil has been shown to exhibit large settlement and reduction in bearing capacity on inundating with water. It has been shown that while reduction in bearing capacity is observed as moisture content is increased, the foundation failures observed were mainly, due to large excessive total and differential settlements. It has also been observed that the strip type of foundation used for most lightly loaded buildings on the site, lacked the rigidity needed for foundation on collapsible soils. Furthermore it has been shown that variation in moisture content of the soil across the seasons is minimal from 2.5m downwards. A design criteria for lightly loaded foundations on collapsible soils is therefore put forward. A survey of alternative foundation types has been undertaken and the most favoured of these foundations was that using spread footings at depths not. suqceptible to Tuch variation in moisture content. It has also been found that attention need also be focussed on environmental factors such as landscaping and long term site and plumbing maintenance, if foundation stability is to be guarranteed. A typical design of the most favoured foundation was undertaken and found to impose a bearing pressure of 47KN/m2 and an angular distortion of 1:556 which are less than the permissible values