The problem of human response to blast induced vibrations in tunnel construction and mitigation of vibration effects using cautious blasting in half-face blasting rounds

Blast induced ground vibrations generated by explosives in tunnel construction may cause structural damages in or close to urban areas. Therefore, the aim in blasting must be to suppress the vibration effects and mitigate the possible hazard on structures. But the psychological character of human response to vibrations involves highly subjective attitudes about what kind of environment is "acceptable" even if no structural damage is occurred. Therefore, we utilize the method of cautious blasting for half-faces that is environmentally friendly, and easy to utilize for tunnel construction. Small charges in this method are detonated sequentially to produce minimum side effects. This method is tested in a tunnel construction in Istanbul with numerous experimental shots. In these experiments, the duration and also quantity of explosives are carefully controlled. Regarding human response, better results are obtained with short durations (about 300 ms) compared to long durations (9000 or 480 ms). The quantity of maximum co-operating explosive charge decreases from 3.088 to 1.744 kg while the vibration levels defined as peak particle velocity (PPV) become more tolerable around 300 ms shot durations.