Supporting the Illinois State Capitol

Construction of the Illinois State Capitol building in Springfield, Ill., began shortly after the end of the Civil War, and was completed in 1888 using construction materials and the means and methods available at that time. The exterior walls consist of large stone blocks mortared together, with brick and mortar used to build the interior walls and columns (Figure 1). Wall and column footings were constructed with mortared stone blocks underlain by an unreinforced concrete leveling pad bearing on shale or hard silt. The unreinforced concrete encountered during the construction project described here was rudimentary and inconsistent; it's solid in some locations and contains voids in others. The Capitol was largely constructed by hand without the sophisticated equipment used today. Due to the thick walls and heavy construction materials used for the Capitol building, bearing pressures up to 30 ksf were calculated for the existing footings.