Authors:

Abstract

Significant safety challenges can arise at tunnelling works as they are conducted in semi-enclosed environments. This study aimed to develop a safety risk assessment framework for drill and blast tunnel construction in Sri Lanka. Tunnelling expert surveys in three sites were used for collecting the necessary data. Initially, a Risk Score Analysis was conducted to identify the critical hazardous events. They were identified as: direct spraying of concrete on eyes and skin, being exposed to noxious dust, and constant exposure to noxious noise. A Bow Tie Analysis was conducted to analyse each critical hazardous event, identifying their causes, preventive measures, recovery measures, and consequences. A probability-based Event Tree Analysis that shows all possible outcomes following the success or failure of protective barriers was also conducted. For example, according to the event tree analysis of ‘direct spraying of concrete on eyes and skin,' there is an overall probability of 19.1% such that significant consequences could be prevented. The research has justified the practicality of these risk analyses for drill and blast tunnelling sites. Also, recommendations are provided for the contractors and workers targeting continuous improvement of safety provisions at tunnelling sites.

Keywords: Tunnel safety, Drill and blast method, Risk score analysis, Bow tie analysis, Event tree analysis