Numerical Insight into the Geotechnical Mechanisms Triggering Failure at the Winter Park Sinkhole in Florida

On May 8^th, 1981, a gigantic sinkhole in Winter Park, Florida (USA), opened up mobilizing 250,000 cubic yards of soil, including extensive damage to two adjacent streets, a three-bedroom house, and car dealership. This catastrophic sinkhole has been referred to in the technical literature as the Winter Park sinkhole. When it stopped growing, the crater reached approximately 107 meters in diameter and 30 meters in depth, causing a devastating $4 million in damage to the community. Numerous site investigation efforts were performed in the vicinity of the sinkhole, and several geotechnical reports detailed the geotechnical characteristics of the site. In this study and for the first time, finite element based numerical investigations were conducted to elucidate the geotechnical failure mechanisms of the Winter Park sinkhole. PLAXIS 2D using the hardening soil small model (i.e., HSSmall, which captures small strain behavior of soils) was selected as the numerical platform for this study. Constitutive soil parameters were determined using published correlations and site-specific subsurface investigation data. Failure was triggered in the numerical model by incrementally increasing the size of a subsurface cavity until collapse of the model occurred. This analysis was aimed to assess the mechanical behavior of soils around cavities associated with stresses, strains, deformations, and excess pore water pressures. The shearing stress paths and evolution of ground surface deformations that triggered the geotechnical failures during the sinkhole formation are presented in this paper.