Analyzing stability of protective structures as the elements of geotechnical tailing pond safety

Abstract

Purpose is the assessment of soil retaining wall stability to ensure geotechnical safety during the radioactive waste tailing pond closure and further recultivation (or rehabilitation) in Kamianske town (Ukraine). Methods. Geomechanical stability of the protective structure has been assessed relying upon the analysis of geological-hydrogeological, engineering-geological, and geotechnical conditions of the certain tailing pond area using a deformation elastic-plastic model of a medium implemented on the basis of finite-element method. For the purpose, the dam slopes have been detalized taking into consideration their geometry as well as changes in vertical section of rock material characteristics in accordance with the earlier geophysical studies; exploration drilling; and engineering-geological surveys. Findings. Stability coefficients of protective tailing pond dam have been identified within the typical areas of a hydraulic structure; it provides high reliability and representativeness of the whole structure health in time as well as under various conditions of the industrial waste water saturation. It has been defined that the stability coefficients varies from ks = 1.372 to 4.758. Comparison of the indicators between 2022 and 2016 demonstrates a tendency of the slope stability coefficient decrease due to water saturation and groundwater level rise. Nevertheless, design characteristics of the structure make it possible to ensure satisfactory a stability coefficient along the whole dam length being 1.13 times higher than the standard one (i.e. ks = 1.250). Originality. The dependence of the tailing pond protective dam stability upon a water supply degree at the forecasted groundwater level rise at the expense of atmospheric and melt water ingress to the tailing pond has been defined. The danger of complete radioactive waste water saturation is a significant reduction in the stability coefficient of the protective structure, which can be supported by predictive modelling data. If strength parameters of a dam material decline for the most critical area then the strength coefficient decreases starting from 1.532 in terms of the current groundwater level down to 1.372 as for the forecasted dam water supply. The figure is more than 10% of its initial stability. Practical implications. The obtained results substantiate the necessity; moreover, they are of practical value while improving hydrological, hydrogeological, and geotechnical monitoring of the analyzed tailing pond to ensure its radiation safety under different conditions of further behaviour during closure, recultivation, or rehabilitation.