Limit State Sinkhole Risk Assessment

A unique sinkhole limit state risk assessment methodology has been developed that incorporates: (1) an evaluation of primary triggering mechanisms; (2) assessment of key risk factors (past failure history, soil-bedrock type, groundwater flow, and hydrology); (3) an evaluation of human activities (site development, drainage changes, construction activities); and (4) and most importantly, the impacts of extreme weather (precipitation, temperature, flash flooding, erosion). Baseline load and resistance parameters for a given karst area or site are analyzed for normal pre-failure or typical failure limit states. Various load and critical resistance factors are then applied to determine possible failure limit states. A simple graph or map of each critical load or resistance factor with time or location is developed for key parameters such as sinkhole failure history, precipitation, groundwater fluctuations-flow, surface runoff, drainage changes, and any relevant activity by man. The average normal range, upper and lower damage-failure thresholds are identified along with the upper and lower extremes that are associated with major failures and disasters. By overlaying the various load-resistance factors, critical limit states and sinkhole risk are determined for any given area and combinations of loading-resistance conditions. The use of the sinkhole limit state risk assessment methodology is presented for a PA33-Tatamy Road Pennsylvania sinkhole case study.