Structural behavior and damage assessment of residential foundations subjected to subsidence

Coal mining in southern Illinois has resulted in many houses being exposed to subsidence damage. Insurance and coal companies compensate home owners for damage, and thus they are interested in ways to minimize losses. Damage mitigation techniques used in house foundations are effective in minimizing subsidence damage. Various footing damage mitigation techniques were applied to twelve strip foundations constructed above an advancing long-wall mine. Post-tensioning, deformed bars, and steel fibers were used to reinforce three of the footings. Two of the footings were constructed with footing/soil interfaces and one used only plain concrete (control foundation). Construction of the foundations is described. The structural materials used in the foundations were tested to obtain parameters for analytic modeling. The behavior of the foundations was measured by using a tape extensometer. The measured behavior is compared with the costs of the various damage mitigation techniques to establish cost-benefit relationships. The post-tensioned foundation had the least damage but was the most expensive. The deformed bar foundation performed well, but cost only slightly more than the control foundation. The footing/soil interfaces only slightly decreased damage over the control. A need for wall damage mitigation techniques was recognized.