Modified Mat Foundation Design Over Soft Clay

The case history of how design and construction were interdependent on a project involving a 26-story apartment building over Chicago soft clay is described. A modified mat foundation solution was selected as the most economical and feasible type of foundation for the structure. Due to the high stress levels induced in the soft clay layer from the building weight, an instrumentation program consisting of settlement readings, pore pressure measurements, and inclinometer readings was necessary to monitor performance of the structure and soil during construction. A reasonable factor of safety required that significant pore pressure dissipation and shear strength increase occur in the soft clay layer during construction of the project. The results obtained verified the design approach.