Optimising Tunnel Blasting: Practical Approaches to Vibration Control and Safety in Underground Works

Blasting-induced vibrations pose a critical challenge in tunnel construction, where the confined environment and unique excavation conditions distinguish underground work from surface operations, such as open-pit mining. This paper focuses on vibration control and prediction, specifically in tunnelling, highlighting the distinct requirements and practical solutions for safe and efficient underground excavation. Tunnel blasting is a highly cyclic process. Most of each work cycle is devoted to drilling, loading, and preparing the initiation system, while the detonation, which generates most of the vibrations, lasts only a few seconds. Each blast produces a sequence of extremely short impulses, separated by variable silent intervals, whereas drilling generates continuous, though considerably lower-intensity, vibrations. Rock fragmentation is achieved through impulsive pressures from explosive gases, with peak pressures typically ranging from 10⁵ to 10⁶ MPa over a few milliseconds. Each charge releases several megajoules of energy within microseconds, detaching and fragmenting rock volumes from hundreds of litres to several cubic metres. Depending on tunnel dimensions and excavation sequence, groups of 10–150 charges may be detonated in seconds. This emphasises the need for precise source-level vibration control and accurate prediction of vibration propagation to surrounding structures. The paper provides an overview of tunnelling-specific blasting techniques and equipment and presents selected practical approaches that have proven effective in reducing vibrations. By concentrating exclusively on underground works, this study bridges the gap between general blasting experience and the specific demands of tunnel excavation, offering valuable guidance for engineers seeking safer, more controlled, and efficient construction practices.