Abstract:
Construction industry has been responsible for a significant amount of accidents, injuries and
other safety related issues at work place, of which the consequences can be fatal or severe.
Tunnel construction is one of the most advanced fields of subsurface constructions in the world.
However, the tunnel construction works lead to serious safety challenges due to their semi
enclosed environment. Hence, continuous improvement of safety provisions at tunnelling work
is vital for preventing hazards. This research study is aimed at conducting a safety risk
assessment for drill & blast tunnel construction which is the commonly used tunnelling method
in Sri Lanka. Tunnel Construction in Broadlands Hydropower Project is taken as the main study
area. A questionnaire survey is conducted with tunnel experts in order to identify the most
critical hazardous events. It uses hazard severity and hazard likelihood rating categories
developed for the drill & blast tunnelling method to come up with a risk score for each hazard.
The risk score value for a hazardous event is calculated multiplying the hazard severity and
hazard likelihood ratings. Based on the resultant risk score values, critical hazardous events are
identified. Here ‘being exposed to noxious dust’ and ‘direct spraying of concrete on eyes or
skin’ have been identified as critical hazardous events. A detailed risk assessment which
specifically addresses what are sources/causes of the hazard, their preventive measures (prior
to event), recovery measures (post- event) and the consequences is conducted and graphically
represented using a Bow Tie diagram. A probabilistic risk assessment is also planned to conduct
via Event Tree Analysis. Finally, using the Bow Tie and Event Tree analysis results, a set of
recommendations are presented to develop a proactive safety culture in the drill & blast tunnel
construction industry in Sri Lanka.