Risk post-assessment and management of a waste slag site under extreme scenarios

The failure of waste slag is a disaster that impacting both environment and lives. In China, there are many waste slags after the engineering projects such as the construction of railway and road. Although the treatment of the waste slags obeys the regulations that the government have established, some accidents still happened. In order to ascertain the reason for the unexpected failure, the inverse analysis is needed to check the initial stability status and the level of potential damage of slag sites. The conventional failure probability of waste slag site is analyzed based on relevant factors that have considerable uncertainty and are difficult to quantify. Therefore, assuming that the failure of slag sites will occur under extreme scenarios, a methodological procedure of risk post-assessment and management under extreme scenarios is proposed in the paper, which indicates that risk management is necessary during the procedure of design, operation, and maintenance of the slag site. In this method, the Tsunami-Squares method was used to simulate the movement process of tailings sand due to the dam failure and generate hazard mapping with the intensity parameters (flow path and thickness). The integrated risk of economic loss, fatalities, and contamination to children and adults was considered in the paper. Following the As Low As Reasonably Possible principle, the F–N diagram was divided into five domains to represent four different risk acceptable conditions, and accordingly, the risk treatment measures were proposed respectively for waste slag sites. A risk management mode of “risk-sharing community” was presented that sparkplugged the representatives of multi-stakeholder to participate in the risk management. The proposed methodological procedure of risk analysis and management could provide effective supports to the decision-making of the design factors and the implementation of stabilization and monitoring of waste slag sites.